Recent Work in the Field of High Pressures\*

P. W. Bridgman

Submitted 1947 | SovietRxiv: ru-194701.01617 | Translated from Russian

Full Text

Recent Work in the Field of High Pressures*

P. W. Bridgman


The influence of pressure on thermal effects	346
Electrical effects of high pressure	350
Magnetic effects at high pressure	370
Optical effects of high pressure	373
The influence of pressure on chemical reactions	380
The influence of pressure on biological effects	394

The Influence of Pressure on Thermal Effects

Any separation of a thermal effect from a mechanical one is to a considerable extent arbitrary and is a matter of convenience. Indeed, all $P$-$V$-$T$ relations and phase transitions described in the preceding sections as mechanical effects could with equal justification have been described also as thermal ones. In the present section there will be discussed a comparatively small number of such works whose belonging here would be clearly confirmed by their title.

1. The Influence of Pressure on Heat Capacity

If the complete $P$-$V$-$T$ dependence is known, then the change of heat capacity with pressure can be found thermodynamically by differentiation, and this is the most usual method of procedure. In addition, mainly for gases, there are also direct experimental measurements of heat capacity under pressure.

Hoxton^398 compared the values for the heat capacity of oxygen and air at $26^\circ$ and between 20 and 100 atm, calculated from $P$-$V$-$T$ data, with those found experimentally.

In his opinion, differentiation of $P$-$V$-$T$ data is so unreliable that experimental data should be preferred. Workman^399 described a new dynamic method for measuring heat capacity

* Conclusion. See Uspekhi Fizicheskikh Nauk, vol. XXXI, no. 1, p. 53; no. 2, p. 210.
P. W. Bridgman, Reviews of Modern Physics, 18, No. 1, 1 (1946).

and applied it to oxygen at 26° up to 100 atm. Creitz and Mackey^400 described a dynamic method for determining the heat capacities of gases at pressures up to 1000 atm and applied it to nitrogen up to 200 atm.

Newitt^401, from data on explosions of mixtures of carbon monoxide and hydrogen with air at initial pressures up to 170 atm, derived values of the molecular heat capacity of nitrogen, water vapor, and carbon dioxide up to 3000° C.

Workman^402 determined, by means of his dynamic method, the heat capacity of oxygen, nitrogen, and hydrogen up to 60° and 130 kg/cm². At any constant temperature $C_p$ increases approximately linearly with density, this increase being smallest for hydrogen (4% for the maximum pressure) and greatest for oxygen (20%). Godnev^403 obtained good agreement between experimental and calculated data for $C_p$ of oxygen up to 200 atm. Workman^404 experimentally determined $C_p$ for carbon dioxide up to 65.3 kg/cm² and found that $C_p$ depends strongly on temperature. $C_p$ for helium does not change appreciably at pressures between 10 and 120 kg/cm².

Golubev and Kul’chitskii^405 determined the heat capacity of gaseous mixtures $3\mathrm{H}_2 + \mathrm{N}_2$ up to several hundred atmospheres between 25 and 100°. The heat capacity increases with pressure to a greater extent at low temperatures. Here there is agreement between experiment and calculation up to 200 atm and divergence thereafter.

Zlunitsyn^406 determined the heat capacity of ammonium chloride and ammonium bromide up to 1425 kg/cm². I am acquainted with the article only from the abstract, and comparison with the original is desirable. The heat-capacity measurements were made within 0.01° of the discontinuity point; the discontinuity is apparently finite and indicates a phase transition. For $\mathrm{NH}_4\mathrm{Cl}$ the temperature of the discontinuity point decreases by 14° at 1525 atm, and for $\mathrm{NH}_4\mathrm{Br}$ by 28° at 1430 atm.

This is completely contrary to my results. I found that the discontinuity point rises with pressure for the chloride and decreases for the bromide. It is possible that in the abstract a discontinuity of the second kind, which at atmospheric pressure occurs below 0° C, has been confused with a phase transition occurring at a temperature above 100°. In a second paper Zlunitsyn^407 measured the heat capacity of $\mathrm{NH}_4\mathrm{J}$ between $-60$ and $10^\circ$ for four pressures up to 1550 kg/cm² and, from thermal data, determined the displacement with pressure of the temperature of the Curie point (a transition of the second kind?) and of the phase-transition point. The first point decreases, while the second increases. In the latter case these results are, at least qualitatively, in agreement with my data.

Trapeznikova and Milotin^408 measured the heat capacity of $\mathrm{CH}_4$ and $\mathrm{CD}_4$ at pressures up to 2000 kg/cm² and at temperatures from 12 to 30° K, i.e. in the solid phase. $\mathrm{CH}_4$ has two anomalies: the first shifts from 20.6° K to 30° K at 2000 kg/cm², and the second from 18.5° K to 27° K with the same increase in pressure.

CD$_4$ at $1\ \text{kg}/\text{cm}^2$ is equivalent to CH$_4$ at $1410\ \text{kg}/\text{cm}^2$, as far as the first anomaly is concerned. The thermal anomalies are connected with anomalies of density.

Matveenko$^{409}$ wrote a theoretical article in which he gives a method for extrapolating data on the compressibility of hydrogen, nitrogen, methane, and nitrogen–hydrogen mixtures to high temperatures and pressures, and for calculating heat capacity.

CITED LITERATURE

L. G. Hoxton, Phys. Rev. 36, 1091 (1930). Notes on the variation of the heat capacity of gases with pressure, derived from compressibility data.
E. J. Workmann, Phys. Rev. 36, 1183 (1930). A new method for measuring the change of the heat capacity of gases $(C_p)$ with pressure.
N. W. Krase and B. H. Mackey, J. Am. Chem. Soc. 52, 108 (1930). Heat capacity of gases at high pressures.
D. M. Newitt, Proc. Roy. Soc. 125, 119 (1929). Molar heat capacities at high pressure.
E. J. Workmann, Phys. Rev. 37, 1345 (1931). Measurement of the heat capacity $(C_p)$ of oxygen, nitrogen, and hydrogen with pressure.
I. N. Godnev, Zhurn. obshch. khim. 1, 634 (1931). Heat capacity of gases at high pressures.
E. J. Workmann, Phys. Rev. 38, 787 (1931). Change of $C_p$ of nitrogen and hydrogen with temperature at pressures of $65.3\ \text{kg}/\text{cm}^2$; heat capacity of helium as a function of pressure.
I. F. Golubev and N. V. Kulachinskii, Zhurn. khim. prom. 15, 36 (1938). Heat capacity of a nitrogen–hydrogen mixture $(3\text{H}_2+\text{N}_2)$ at high pressures.
S. A. Zlunitsyn, Zhurn. eks. teor. fiz. 8, 794 (1938). Heat capacity of bromic ammonia and chlorine-bromic ammonia under pressure.
S. A. Zlunitsyn, Zhurn. eks. teor. fiz. 9, 72 (1939). Heat capacity of NH$_4$J under pressure.
O. N. Trapeznikova and G. A. Milotin, Nature, 144, 632 (1939). Heat capacity of a metal under pressure.
A. A. Matveenko, Zhurn. khim. prom. 16, 23 (1939). Determination of the heat capacity of gases at high pressures.

2. VARIOUS THERMAL EFFECTS OF HIGH PRESSURE

Saunders$^{410}$ investigated (theoretically) natural convection at high pressures; applying dimensional analysis, he showed how convection in large systems can be obtained from experiments on small models when the pressure of the medium (air) is increased. Results are given up to $700\ atm$, using Michels and Gibson’s data on the viscosity of air as a function of pressure; but the author warns that data above $100\ atm$ should be used cautiously, since it is not known how the thermal conductivity of air increases with pressure, as it has not yet been measured.

Basse[^411] measured the energy expenditure necessary to maintain a spiral heating element, arranged along the axis of a cylindrical bomb, at a temperature of 600° C in an atmosphere of hydrogen or nitrogen at various pressures up to 6000 kg/cm². The energy expenditure increases with pressure at a steadily decreasing rate, possibly asymptotically. In the case of nitrogen, and at the maximum pressure, it is 62.5% greater for hydrogen than for nitrogen. Basse believes that at low pressures the main part of the losses is due to convection; he notes that the losses are approximately proportional to the total mass of the medium.

Guzik[^415] experimentally constructed an enthalpy diagram for nitrogen within the pressure range from 60 to 200 atm and at temperatures from 115° to 292° K. Up to 60 atm his results coincide with those of the Bureau of Mines.

Starr[^416], working in my laboratory, determined the effect of pressure up to 12,000 kg/cm² at room temperature on the thermal conductivity of a series of metals. He considerably improved the technique with which I had worked earlier; I used two methods: one for metals of low conductivity and the other for metals of high conductivity. The latter method gave unsatisfactory results.

Starr’s improved method for very heat-conducting metals eliminates several sources of error in my method and shows the erroneousness of my conclusions that, for such metals, the Wiedemann–Franz ratio between electrical conductivity and thermal conductivity may both increase and decrease with pressure. Starr found for copper, silver, and gold that the ratio of thermal conductivity to electrical conductivity increases by approximately 1% up to 10,000 kg/cm².

Allen and Ganz[^414] investigated the effect of pressure on the thermal conductivity of helium II. In this case the pressure was, of necessity, limited to an interval up to 25 kg/cm². It is known that the apparent thermal conductivity is a function of the temperature gradient. Working with a constant temperature drop of 0.001° per cm, they found that below 1.63° K the pressure coefficient for the thermal conductivity is positive, and above it negative. The explanation is complicated and is connected in some way with the transfer of the mass of the liquid.

Budengol’tser, Sage, and Lacey[^415] measured the Joule–Thomson coefficient for methane between 70 and 220° F at six pressures between 20 and 175 atm, and, for a table of various thermodynamic functions, which can be calculated from the Joule–Thomson coefficient.

These same authors[^416] determined, for the same parameters, the Joule–Thomson coefficient for three mixtures of ethane and methane.

Danilend and Luke[^417] developed an expansion method for determining enthalpy and measured the enthalpy of benzene up to 200 atm and 290° C, i.e., up to a temperature 1.2 times greater than the critical temperature.

Volarovich⁴¹⁸ determined the effect of heating various rocks and minerals up to 1100° at pressures up to 1000 atm. The volcanic rocks showed no changes. Sedimentary rocks changed color and microstructure the more, the higher the pressure had been. Rhodochrosite oxidized and was transformed into pyrolusite.

Budenholzer, Botkin, Sage, and Lacey⁴¹⁹ measured the Joule–Thomson coefficient for three mixtures of methane and propane between 70 and 310°F up to 105 kg/cm² and calculated the partial enthalpies of methane and propane in their mixtures.

CITED LITERATURE

O. A. Saunders, Engineering, 138, 436 (1934). Natural convection at high pressures.
J. Basset, Comptes rendus, 203, 1338 (1936). Heat transfer in nitrogen and hydrogen at pressures up to 6000 kg/cm².
I. M. Guzak, Physik. Zschr. Sowjetunion 11, 60 (1937). Enthalpy diagram of nitrogen from 60 to 200 atm.
C. Starr, Phys. Rev. 54, 210 (1938). Pressure coefficient of the thermal conductivity of metals.
J. F. Allen and E. Ganz, Proc. Roy. Soc. 171, 242 (1939). Effect of pressure on the thermal conductivity of liquid helium II.
R. A. Budenholzer, B. H. Sage, and W. H. Lacey, Ind. Eng. Chem. 31, 369 (1939). Phase equilibria in hydrocarbon systems. Joule–Thomson effect for methane.
R. A. Budenholzer, B. H. Sage, and W. H. Lacey, Ind. Eng. Chem. 31, 1288 (1939). Phase equilibria in hydrocarbon systems. Joule–Thomson effect for mixtures of methane and ethane.
E. R. Gilliland and R. V. Lukes, Ind. Eng. Chem. 32, 957 (1940). Effect of pressure on the enthalpy of benzene.
M. P. Volarovich, Proceedings of the Third Conference of the Experimental Mineralogical and Petrographic Institute, Geological Sciences, USSR Academy of Sciences, 45–54 (1940). Heating minerals and rocks at pressures up to 1000 atm.
R. A. Budenholzer, D. E. Botkin, B. H. Sage, and W. N. Lacey, Ind. Eng. Chem. 34, 878 (1942). Phase equilibria in hydrocarbon systems. Joule–Thomson effect for the methane–propane system.

ELECTRICAL EFFECTS OF HIGH PRESSURE

1. EFFECT OF PRESSURE ON THE ELECTRICAL RESISTANCE OF SOLIDS

Many theoretical works have been written in which the methods of wave mechanics were applied in attempts to explain the effect of pressure on resistance. However, this does not fall within our task, and therefore we shall not dwell on these works, except for a brief summary at the end of the present section.

With the exception of my own works, there are comparatively few new experimental works in this field, and most of them are of an incidental nature. Of these incidental works

mention should be made of the work of Michels’ laboratory. Michels and Jensen^420 carried out a very careful investigation of the influence of annealing temperature (up to 400°) on the change in the electrical resistance of pure gold at pressures up to 2000 kg/cm². This investigation was undoubtedly prompted by the desire to test the suitability of gold as a material for making a precision resistance manometer.

At the end of the period covered by my book, Michels wrote an article on the influence of pressure on electrical resistance, in which he emphasized the irregularity of the change of resistance with pressure that can be caused by the corresponding treatment; apparently, at that time it was believed that the change of resistance was not suitable for exact measurements. The spirit of the work of Michels and Jensen was the opposite, namely to find whether the behavior of resistance with pressure, under suitable conditions, could be used for exact measurements.

Michels and Jensen found a 4% change in resistance as a result of annealing and a 3% increase in the pressure coefficient; a noticeable hysteresis of resistance with pressure is always observed after the first application of pressure to the annealed material.

The influence of pressure was studied at four temperatures from 25 to 100°, and complete tables of results are given.

Most of this work with gold was reproduced in Jensen’s doctoral dissertation^421; additional measurements were also made with manganin up to 1000 kg/cm². The normalization procedure, which consisted in repeated compression and heating of the material, was carefully investigated; in compression cycles up to 1000 kg/cm², a zero stability of 1/20 kg/cm² was obtained, and for cycles of 2000 kg/cm²—1/10 kg/cm².

Michels and van Sante^422 measured the influence of pressure, in their usual pressure range, on three alloys of nickel and iron between 25 and 125°C. The pressure coefficient decreased by more than a factor of three with increasing temperature and passed through a noticeable maximum with increasing nickel content at 45% nickel.

Fisher^423 measured the change in the pressure coefficient for Pb, W, Mo, Cu, Fe, and constantan down to the temperature of liquid hydrogen. He reached 150 kg/cm². The pressure was produced by compressed hydrogen from a cylinder. In general he found a noticeable increase of the pressure coefficient with decreasing temperature and, surprisingly, this increase is greatest for the metals with the highest characteristic temperature; thus, the coefficient for tungsten at 20°K increases threefold in comparison with room temperature.

My later measurements did not confirm his numerical data; I think that his pressures were too small to give accurate results. The measurements are too difficult for such small pressure changes as these.

Braunbek^424 measured the electrical resistance of mercury under the pressure of its vapors up to 600°. In the same year Birch^425 published his ...

doctoral dissertation under my supervision, in which the resistance of liquid mercury between 0 and 1200° and at pressures up to 4000 kg/cm² was determined. The mercury was in a quartz capillary wound with a heating wire and placed in an autoclave. The temperature was measured by thermocouples introduced into the high-pressure vessel.

The work gives tables for the resistance, and also for the temperature coefficient and the pressure coefficient within the range of the measurement parameters. These three quantities increase with increasing temperature and decrease with increasing pressure.

At the upper boundary of the interval the resistance of the vapor was also determined. The critical point, determined by extrapolation, is equal to 1460 ± 20° C and 1640 ± 50 kg/cm².

Basse[^426] determined the resistance of a rod of zirconium oxide containing 10% thorium oxide and 10% yttrium oxide, at a temperature of 900° C and pressures up to 4000 kg/cm². The maximum pressure increases the resistance from 4300 ohms at atmospheric pressure to 1,500,000 ohms.

Jost and Nelep[^427] measured the resistance of AgCl and AgBr at 300° C up to 300 atm. The resistance increases with pressure; the pressure coefficient of the chloride is $2.5 \cdot 10^{-4}$ and that of the bromide $3.5 \cdot 10^{-4}$. They gave a theoretical expression agreeing to within 25% with the experimental data.

Holmes and Allen[^428] measured the resistance of a selenium single crystal up to 700 kg/cm². For short holding times a noticeable hysteresis is observed, disappearing when the experiment is continued to 30 minutes or longer. Under these conditions the resistance decreases linearly with pressure, the coefficient being $3.1 \cdot 10^{-4}$. This is apparently the largest of the known coefficients.

Keene, in the already mentioned[^350] article on the phase diagram of binary alloys of sodium and potassium, gave data concerning the change in resistance up to 10,000 kg/cm² of liquid sodium-potassium alloys for four characteristic compositions. These are “measured” resistances, including the compressibility of the glass capillary. The resistance decreases with increasing pressure, and the coefficient is noticeably smaller than for the pure components. Keene suggests that the liquid alloy rich in potassium (85.5%) may have a resistance minimum at a pressure considerably lower than 25,000 atm—the pressure at which pure potassium has a minimum.

Wilson, in connection with his already noted[^240] measurements of the effect of pressure on the transition of an ordered phase into a disordered one in alloys, gives numerous graphs for the resistance as a function of temperature and pressure up to 10,000 kg/cm² for four alloys. These alloys are: CuAu, Cu₃Au, CuZn, and Cu₄Zn. The resistance of all the alloys decreases with pressure. With the exception of regions with internal changes, the resistance varies approximately linearly

with pressure. In all cases the pressure coefficient increases with temperature at an increasing rate (the curve is concave upward). In the case of CuAu and Cu$_3$Au there is a noticeable acceleration of the increase above 250°. It should be recalled that for pure metals the pressure coefficient is almost independent of temperature.

Minz$^{429}$ measured the resistance of various carbonaceous substances—artificial graphite, coke, petroleum coke, and anthracite—between 20 and 2100° up to 350 kg/cm$^2$.

High pressures reduce the influence of temperature. The results, as explained, depend on ionization in microscopic cracks.

Lazarev and Kan,$^{430}$ using a method already described in the section on technique,$^{12}$ studied the influence of pressure up to 1750 kg/cm$^2$ on the transition of tin and indium into the superconducting state. The superconducting temperature of tin at 1750 kg/cm$^2$ is lowered by 0°.095; the pressure coefficient that can be obtained from these data agrees with the value found by Kizom at a lower pressure, so that the effect apparently depends linearly on pressure. For indium only preliminary data were obtained.

It is necessary to note here two papers from Michels’s laboratory,$^{488,493}$ which will be considered in detail later in connection with other questions, and in which measurement of the influence of pressure on resistance was carried out in order to determine the displacement of the Curie point. These articles give complete data for the influence of pressure up to 2650 atm in the temperature interval encompassing the Curie region, for a 70—30% Ni—Cu alloy and for monel metal containing Ni 68%, Cu 29%, Fe 1.6%, Mn 1.0%, Si 0.1%, and C 0.15%. The pressure coefficient is negative; various anomalies connected with the Curie point were found.

My work in this field was carried out in the early years of this period in the usual interval up to 12,000 kg/cm$^2$, and later up to 30,000 kg/cm$^2$. A technique for measuring resistance at higher pressures had not yet been developed; the difficulties consisted in the need to select a suitable transmitting medium and to insulate the electric leads so that they could withstand the stresses.

In 1931$^{177}$ I published measurements of the influence of pressure on the resistance of TiN and TiC; the resistance of both substances decreases with pressure, and this decrease is unusually small and, within the limits of experimental error, linear. In the same work the influence of pressure on the resistance of a magnesium single crystal in different crystallographic directions was determined. The resistance falls with pressure and can be expressed by the usual quadratic equation in pressure. The pressure coefficient is almost the same in both crystallographic directions, and is somewhat higher in the direction perpendicular to the hexagonal axis. Approximate equality in the two directions might have been expected from the fact that the structure of a magnesium crystal is that of close-packed spheres. However, small

deviations from isotropy occur in the abnormal direction, and the resistance has its smallest value perpendicular to the cleavage planes, i.e., parallel to the hexagonal axis.

In 1932,^[181] the effect of pressure on the elements Cb, Rh, Ru, Cr, and As and on alloys of silver with gold was measured. The first three elements show a normal decrease of resistance with pressure, the value of the pressure coefficient corresponding to the normal magnitude for refractory metals. Chromium gives noticeable anomalies, detectable only in very pure metal; earlier I measured the resistance of chromium of a lower degree of purity and found no anomalies. The curve of the change in the resistance of pure chromium with temperature at atmospheric pressure has an S-shaped form, with a minimum and a maximum lying close together near $0^\circ$, and is very reminiscent of the curve of the specific volume of water in the region of considerable supercooling. The resistance decreases at all temperatures with increasing pressure, but, owing to the character of these curves at atmospheric pressure, a complex intersection of the curves is obtained. The effect of pressure on the resistance was measured between $-80$ and $90^\circ$. The pressure coefficient has a sharp maximum at $-40^\circ$, where it is almost twice as large as at the highest temperature. The effect was also investigated in three different orientations of a bismuth single crystal. The effect is very irregular and not reproducible. Clearly expressed time effects are present, sometimes so large that the initial application of pressure causes an increase in resistance instead of a decrease, as occurs after a more or less stationary state has been established. The dependence between pressure and resistance can be represented approximately by three straight lines with different slopes, as can the dependence between volume and pressure. The effect of pressure on the resistance is smallest for that orientation in which the hexagonal axis is perpendicular to the direction of the current.

The action of pressure on three alloys of gold and silver gives nothing unusual; the resistance decreases with pressure and can be expressed by the usual quadratic equation. For compositions $50:50$ the coefficient is smaller than for other compositions. The resistance exhibits small anomalies, as was found for the effect of pressure on volume; in general, such anomalies are appreciably smaller for resistance than for volume changes, partly, probably, owing to the greater sensitivity of volume changes.

In 1932,^[431] I published investigations on the effect of pressure up to $7000\ \mathrm{kg/cm^2}$, at temperatures down to the temperature of liquid oxygen, $90^\circ\mathrm{K}$, on the resistance of the following fifteen metals: Pb, Mg, Al, Ag, Au, Cu, Ni, Fe, Pd, Cb, Pt, Rh, Mo, Ta, and W. The pressure was transmitted by helium, chiefly because any other substance freezes at such temperatures and pressures.

There were considerable technical difficulties, mainly in connection with the leakage of helium due to the mechanical imperfection of the steel. The lead to the specimen was made through a connecting tube on the block, in which the insulation was kept at room temperature. In general, the coefficient of pressure resistance increases at low temperature, but to a considerably lesser extent than was found by Fischer[^42]; moreover, the character of the change as a function of the metal does not agree. Fischer found the greatest increase for tungsten and tantalum, whereas I found a decrease for these two metals. I have already indicated that this is explained both by Fischer’s use of low pressures and by the absence of normalization under these conditions. (Normalization also does not occur at pressures several times greater than those used by Fischer.)

Two questions are of interest in connection with the influence of pressure on resistance at low temperatures: whether pressure induces a state of superconductivity at temperatures higher than usual, and whether it may be assumed that the suspected minimum of resistance will be observed at lower pressures when the temperature is lowered. The measurements gave a negative answer to both questions.

Following the investigation of the resistance of fifteen metals (most of them of the cubic system) at low temperatures, measurements were made[^42] of the resistance of seven non-cubic single crystals along different orientations in the same range of temperatures and pressures. These were Zn, Cd, Sn, Bi, Sb, As, and Te. With the exception of tellurium, which is not a metal, the effect on the six metals is the same as had been found earlier: at low temperatures the pressure coefficient is arithmetically larger, whether positive or negative, than at high temperatures. As regards the difference in the influence along different directions, it is known that pressure at ordinary temperatures smooths out the difference in the resistances along different directions for zinc, cadmium, and antimony, and increases this difference for bismuth and tin.

At low temperatures this smoothing for the first three metals becomes less noticeable, but for the latter two the difference increases.

The effect of pressure on tellurium is very large, and the resistance at $12\,000\ \mathrm{kg/cm^2}$ is of the order of one percent of its value at atmospheric pressure. In a first approximation the logarithm of the resistance changes linearly with pressure; the rate of decrease of resistance with pressure is considerably smaller at $-78$ and $-182^\circ$ than at $0$ and $95^\circ$. This causes an intersection of the curves and a change in the sign of the temperature coefficient with increasing pressure. These effects in tellurium do not depend noticeably on the direction in the crystal.

In 1935[^183] I published my first measurements in a wider pressure range, up to $20\,000\ \mathrm{kg/cm^2}$.

The apparatus did not differ radically from that on which the experiments up to $12\,000\ \mathrm{kg/cm^2}$ had been carried out; it was made of considerably stronger steel and, for greater strength, was made without any supply tubes or side outlets.

The resistance of gold, silver, and iron was measured up to $20\,000\ \mathrm{kg/cm^2}$ in comparison with a manganin manometer, in order to obtain confirmation of the regularity of extrapolating its readings from $12\,000\ \mathrm{kg/cm^2}$—the calibration range—to $20\,000\ \mathrm{kg/cm^2}$.

Four metals—gold, silver, iron, and manganin—showed a consistent extrapolation from $12\,000$ to $20\,000\ \mathrm{kg/cm^2}$, whence the conclusion was drawn that linear extrapolation for manganin up to $20\,000\ \mathrm{kg/cm^2}$ was possible, with an error of no more than a fraction of a percent.

Assuming that the readings of the manganin manometer were accurate, we measured the resistance of three other substances: black phosphorus, tellurium, and copper sulfide. It was known that the effect of pressure for these substances is large, and therefore an error in the readings of the manganin manometer would have had comparatively little consequence.

Both black phosphorus and tellurium, judging by their resistance, approach the behavior of metals: the temperature coefficient of resistance changes sign at high pressure, and there are clear indications that at a higher pressure a minimum of resistance will be reached.

Copper sulfide was the first semiconductor investigated at such high pressures. At $30^\circ$, the resistance decreases by almost $10\%$ at $20\,000\ \mathrm{kg/cm^2}$; the effect of pressure is repeatable and reversible, and there is a sharp break in the tangent at $3000\ \mathrm{kg/cm^2}$, the rate of decrease of resistance with pressure above $3000\ \mathrm{kg/cm^2}$ being ten times less than below $3000\ \mathrm{kg/cm^2}$. At $75^\circ$, the resistance also falls, but here there are irreversible phenomena with slow internal changes and creep.

In 1935[^182] I also determined the effect of pressure up to $12\,000\ \mathrm{kg/cm^2}$ on the same intermetallic compounds that were listed above in connection with compression measurements, and also on germanium and silver sulfide.

The resistance of all the intermetallic compounds, with the exception of those noted below, decreases with increasing pressure, the value of the coefficient being of the same order as for pure metals. The resistance of $\mathrm{Mg_3Al_2}$ increases with pressure at both temperatures; the coefficient for $\mathrm{Ag_5Zn_8}$ is numerically unusually small and is negative at $30^\circ$ and positive at $75^\circ$, whereas for $\mathrm{Ag_2Al}$ it is positive at $30^\circ$ and negative at $75^\circ$. Most of these compounds exhibit the shift of internal equilibrium also found in measurements of volume.

Anomalies in the change of resistance are, in general, less noticeable than anomalies in the change of volume under the experimental conditions. Со-

the resistance of germanium increases with pressure, at a rate increasing with pressure, and with noticeable deviations from a quadratic equation; the increase at $12000\ \text{kg}/\text{cm}^2$ is of the order of 25%. The resistance of silver sulfide decreases strongly with increasing pressure, reaching at $12000\ \text{kg}/\text{cm}^2$ as little as 0.001 of its value at atmospheric pressure.

The logarithm of the resistance is almost a linear function of the pressure.

In 1938,^5 I published measurements on the effect of pressure up to $30000\ \text{kg}/\text{cm}^2$, at 30 and $75^\circ$, on the resistance of the following eighteen metals: Cu, Ag, Au, Fe, Pb, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Hg, Bi, Zn, Sn, and Te.

The last four metals were studied for two directions relative to the single crystal.

The pressure was measured on the basis of a linear extrapolation of the readings of a manganin manometer; since the deviations from linearity of the resistance changes for these metals are large, extrapolation errors play a comparatively small role.

The resistance of the relatively hard metals—Cu, Ag, Au, and Fe—proved to be just as one would have expected from extrapolation from $12000\ \text{kg}/\text{cm}^2$. However, the quadratic equation is not obeyed; moreover, if a substance has a minimum of resistance at high pressure, it is observed at a higher pressure than follows from extrapolation by means of the quadratic equation applicable up to $12000\ \text{kg}/\text{cm}^2$.

For other metals, extrapolation from $12000\ \text{kg}/\text{cm}^2$ succeeds so poorly that it is scarcely advisable.

The minimum of resistance which had been assumed for potassium was found at $25400\ \text{kg}/\text{cm}^2$, i.e., almost $2000\ \text{kg}/\text{cm}^2$ higher than had been determined by extrapolation.

The minimum for sodium was not reached, although it had been predicted at pressures below $30000\ \text{kg}/\text{cm}^2$; if it exists, then apparently it is at pressures above $40000\ \text{kg}/\text{cm}^2$. The resistance of rubidium continues to increase beyond the minimum found earlier, with increasing rate.

The resistance of calcium, strontium, and barium continues to increase (the curvature is upward) in the new interval of investigation; moreover, for barium this increase was interrupted by a small drop near $17000\ \text{kg}/\text{cm}^2$, owing to a phase transition which was also detected volumetrically.

Cesium undergoes a transformation at about $23000\ \text{kg}/\text{cm}^2$; both before and after it the resistance increases with increasing pressure. The decrease of resistance with pressure therefore appears to be an effect possibly not directly connected with the crystal lattice.

The jump in resistance at the transformation is directed upward, while the jump in volume is downward. This is the first example of a completely anomalous effect;

usually the discontinuity in resistance along the direction coincides with the discontinuity in volume. A second example of the same anomaly was found later for bismuth. At the first phase transition of bismuth I into bismuth II the resistance falls, which is normal, but unusually strongly, by about a factor of six. For the second transition of bismuth II into bismuth III the resistance increases by a factor of 2.5, which is abnormal. In both modifications II and III the pressure coefficient is negative.

The resistance of solid mercury decreases with pressure within limits normal for soft metals in view of their position in the periodic table.

By a fortunate circumstance, measurements of resistance made it possible, with unusual accuracy, to establish a point on the melting curve of mercury at a pressure almost twice as great as the maximum pressure of previous experiments. The melting curve of mercury is unusually straight and can be extrapolated with greater than usual accuracy. The accuracy of the extrapolation along the melting curve gave independent confirmation of the supposition that the linear extrapolation of a manganin manometer gives only a small error.

At high pressures the ratio of the resistances in different directions changes for a zinc single crystal; namely, the resistance along the hexagonal axis becomes smaller than that for directions perpendicular to it. In a tin single crystal the resistance in both directions decreases smoothly over the whole pressure interval, and the ratio of the resistances in different directions remains practically unchanged.

A single crystal of antimony is the only known example of a metal whose resistance passes through a maximum as pressure is increased; this maximum occurs at pressures that are lower the more nearly the direction of measurement approaches the perpendicular to the crystal axis. The pressure of the maximum depends strongly on temperature. The resistance of a tellurium single crystal decreases at $30\,000\ \mathrm{kg/cm^2}$ by almost a factor of six hundred; it is probable that the temperature coefficient of resistance changes sign somewhat above $30\,000\ \mathrm{kg/cm^2}$.

In 1939,[^20] I reported results, published a year later, on the establishment of fixed pressure points for a new interval (the phase transitions of bismuth) and on an accurate determination of the change in the resistance of manganin. It turns out that, with linear extrapolation from $+7600$ to $25\,000\ \mathrm{kg/cm^2}$, the pressure obtained is smaller by one or two percent. The exact magnitude of the deviation varies depending on the specimen of manganin, and each coil must be calibrated separately. It should be noted that the deviation from linearity occurs in the anomalous direction and shows that the curve of resistance as a function of pressure for manganin is concave with respect to the pressure axis, instead of being convex, as in all other known cases with a positive pressure coefficient.

Finally, one should note attempts, in connection with shear experiments350, to bring the limit of resistance measurements up to 50,000 kg/cm². The method consisted in measuring the resistance of a thin disk placed between a steel punch and a rectangular steel block. Only rough qualitative results were obtained. Apparently, in some cases, especially for bismuth, there may be a very large surface resistance in the highly disorganized surface layer—of the order of a thousand times greater than the resistance of a massive disk. This surface film, despite its disordered structure, is capable of showing breaks in the resistance curve when passing through polymorphic transformations. The resistance of the surface film decreases noticeably with increasing pressure, although the resistance of massive bismuth increases. On the other hand, other metals may have a significantly smaller surface resistance; for example, the surface resistance of silver practically disappears at pressures above 40,000 kg/cm².

The following summary of theoretical explanations of the influence of pressure on electrical resistance does not claim to be complete, but aims only to point out the nature of the phenomena considered in the works, without entering into the argumentation.

Honda, Nishina, and Hirone in 1932433 and Honda and Hirone in 1938434 analyzed the influence of pressure on resistance, checking their theory against my data.

The method consists in estimating the effect of pressure on various coefficients in Sommerfeld’s equation for resistance. They found that fairly good agreement with experiment was obtained, but apparently this agreement cannot serve as an argument in favor of the assumed value of the basic idea, because the final mathematical expression contains two arbitrary empirical constants, one of which is chosen so as to give the experimentally determined slope of the resistance curve as a function of pressure at the beginning of this curve. The difference between their calculated values and the experimental data increases with increasing speed as pressure increases.

Kroll435, on the basis of the Bloch–Peierls theory, derived an expression for resistance as a function of pressure containing the lattice parameters, compressibility, and Poisson’s ratio. Neglecting the change of Poisson’s ratio with pressure, he obtained values for the pressure coefficient of silver and gold that are close to the experimental data, and also obtained a positive sign for lithium; but in general the agreement is not very good, and here there may be errors of the order of several hundred percent. Frank436 took up the problem of the pressure coefficient for alkali metals, in particular the difference between sodium and lithium. He attributed this difference to the different form of the energy curves as functions of atomic distances for $2p$ and $2s$ electrons; for lithium $\Delta E$ decreases with decreasing

atomic distances, and for sodium it increases. He calculated the increase in the resistance of lithium at $12\,000\ \mathrm{kg/cm^2}$ with an error of $25\%$.

The theory indicates a possible change of sign of the pressure coefficient for sodium, which is suggested by the experiments, and also an infinite resistance for lithium at some finite pressure, without there being any particular experimental evidence for this.

Mott $^{437}$ developed a general theory of the resistance of metals from the standpoint of wave mechanics and applied it specifically to the effect of pressure. His theory essentially leads to Grüneisen’s expression, which gives satisfactory agreement with experiment. It may be expected that, in general, the pressure coefficient of alloys should be smaller than for pure metals, which is confirmed by experiment. He obtained good agreement with experiment for the effect at low temperatures (my data). The anomalous positive sign for calcium and strontium is explained by special forms of the Brillouin zones, but it is difficult to produce evidence in favor of a positive sign for lithium.

Lennsen and Michels $^{438}$ derived an expression for the dependence of resistance on pressure, based on Nordheim’s theory of resistance (on the basis of wave mechanics). The effect of pressure on the thermal part of the resistance and on the part remaining at absolute zero is considered separately. As regards agreement with experiment, no entirely definite conclusions have been reached, and the final formula contains too many arbitrary constants.

Shaha $^{439,440}$ wrote two papers on the effect of pressure. In the first he bases his analysis on Nordheim’s rigid-ion model, using a screened Coulomb potential.

He obtained good agreement with experiment for silver, gold, and copper and, in general, for metals with low compressibility. Comparison with Kroll’s results shows that the present method of approach should, in general, be preferred to Fermi’s method; apparently, no methods give results for the alkali metals.

In his second paper Shaha describes the application of Bloch’s deformable-ion model; at ordinary temperatures he obtains satisfactory agreement with experiment for sodium, potassium, silver, gold, copper, nickel, lead, palladium, platinum, and molybdenum. He found that at the temperature of liquid air the pressure coefficient should be larger, which is qualitatively in agreement, in general, with my results.

The increase in the resistance of lithium cannot be reconciled with the theory.

Grüneisen $^{441}$ considers the application of his theory specifically to my measurements at low temperature. The residual resistance, owing its origin to impurities, introduces complications that require special discussion.

For pure metals the theory gives constancy of the pressure coefficient and its independence of temperature in the region of high temperatures. At low temperatures the theory leads to a second pressure coefficient, considerably larger and likewise independent of temperature, and to an intermediate transition region. This normal behavior may be so altered by residual resistance that in some cases the pressure coefficient may increase with increasing temperature.

Fairly good agreement is obtained with my low-temperature data, and also with some of Fischer’s data. A positive pressure coefficient of resistance lies outside the scope of the theory.

Cited Literature

A. Michels and M. Lenseen, Physica 2, 591 (1935). The effect of pressure on the electrical resistance of cold-drawn gold wire in various stages of annealing and of soft gold wire.
M. H. Lenseen (Amsterdam 1936). Dissertation. The effect of pressure on the electrical conductivity of metals.
A. Michels and J. W. van Sante, Physica 9, 737, 1942. The effect of pressure on the resistance of three ferromagnetic Fe—Ni alloys.
Ulrich Fischer, Zschr. f. physik. Chemie 8, 207 (1930). On the dependence of the electrical conductivity of metals on pressure at low temperatures.
W. Braunbek, Physik. Zschr. 33, 830 (1932). Electrical conductivity of mercury at high temperatures and pressures.
F. Birch, Phys. Rev. 41, 641 (1932). Electrical resistance and the critical point of mercury.
J. Basset, Comptes rendus 199, 38 (1934). The effect of pressure on the electrical resistance of a rod of impure zirconium oxide in air.
W. Jost and G. Nehlep, Zschr. f. physik. Chemie 34, 348 (1936). Dependence of the ionic conductivity of solids on pressure.
R. M. Holmes and H. W. Allen, Phys. Rev. 55, 593 (1938). The effect of hydrostatic pressure on the resistance of selenium single crystals.
B. V. Milits, Nonferrous Metals 12, 65, 1940. Electrical conductivity of carbon materials as a function of temperature.
B. Lazarev and L. Kan, J. Exp. Theor. Phys. 14, 474 (1944). Measurements at high pressures and low temperatures. II. Superconductivity of tin and indium at a pressure of 1750 kg/cm².
P. W. Bridgman, Proc. Am. Acad. Arts. Sci. 67, 305 (1932). Pressure coefficient of resistance of fifteen metals up to the temperature of liquid oxygen.
P. W. Bridgman, Proc. Am. Acad. Arts. Sci. 68, 95 (1933). The effect of pressure on the electrical resistance of metal single crystals at low temperatures.
K. Honda, T. Nishina, and T. Hirone, Sci. Rep. Tohoku Imp. Univ. 21, 851 (1932). Theory of the change in the electrical resistance of metals caused by hydrostatic pressure.
K. Honda and T. Hirone, Sci. Pap. Inst. Phys. Chem. Research, Tokyo 34, 1292 (1938). Further development of the theory of the change in the electrical resistance of metals produced by hydrostatic pressure.
W. Kroll, Zschr. f. Physik 85, 398 (1933). On the theory of the dependence of the electrical conductivity of metals on pressure.

N. H. Frank, Phys. Rev. 47, 282 (1934). Influence of pressure on the electrical conductivity of alkalis.
N. F. Mott, Proc. Phys. Soc. 46, 680 (1934). Conductivity of metals.
M. H. Lenssen and A. Michels, Physica 2, 1091 (1935). Influence of pressure on the electrical resistance of metals.
N. K. Saha, Ind. J. Phys. 9, 623 (1935). Influence of pressure on the electrical resistance of metals.
N. K. Saha, Trans. Nat. Inst. Sci. India 1, 125 (1936). Investigations on the electron theory of the solid metal.
E. Grüneisen, Ann. d. Physik 40, 543 (1941). Change of the pressure coefficient of the resistance of metals with temperature.

2. INFLUENCE OF PRESSURE ON THE ELECTRICAL RESISTANCE OF SOLUTIONS

Here there are two papers from Tammann’s laboratory which, chronologically, should be assigned to the end of the period covered by my book; since they were not abstracted there, they will be noted now.

Tammann and Tofute 442 measured the resistance of solutions of six acids and ammonia up to 3000 kg/cm² at 0, 20, and 40°; the pressure coefficient of the increase in electrical conductivity, plotted as a function of concentration, reaches a maximum at concentrations that are higher for acids having a large dissociation constant. The pressure coefficient of the degree of dissociation increases with concentration more slowly for ternary than for binary electrolytes.

Pressure increases the friction of ions, with the exception of H- and OH-ions, for which it decreases it.

Tammann and Romann 443 measured, up to 3000 kg/cm² at 20 and 40°, the electrical conductivity of solutions of various concentrations of NaOAc, KCN, BaCl₂, CeCl₃, HgCl₂, NH₄CN, NH₄OAc, and HCN. The increase in electrical conductivity with increasing pressure passes through a maximum for strong electrolytes, the maximum being the less pronounced the greater the concentration and the higher the temperature. HgCl₂ has no maximum.

If a correction is introduced for the dependence of viscosity on pressure, then the electrical conductivity is almost independent of pressure for strong electrolytes, which indicates complete dissociation.

Adams and Hall 444 measured, up to 4000 bar at 0, 25, and 30°, the electrical conductivity of dilute and concentrated NaCl solutions and dilute K₂SO₄ and KCl solutions.

Pressure decreases the electrical conductivity of dilute NaCl solutions and increases it for concentrated solutions. At high pressures the electrical conductivity of NaCl solutions passes through a maximum with increasing concentration. Monosson and Pleskov 445 measured the influence of pressure on solutions in ammonia of LiNO₃, NaNO₃, and KNO₃. The paper is known only from an abstract, and the details of the work are not given.

Brander $^{446}$ worked with solutions of $\mathrm{CO_2}$, $\mathrm{O_2NC_6H_4OH}$ $(\mathrm{CHCO_2H})_2$, $\mathrm{NaHCO_3}$, $\mathrm{O_2NC_6H_4ONa}$, $(\mathrm{CHCO_2Na})_2$, $\mathrm{K_2SO_4}$, and $\mathrm{MgSO_4}$.

For salts of monovalent ions, $R_p/R_0$ does not depend on concentration. The change with pressure is small for $\mathrm{K_2SO_4}$ and greater for $\mathrm{MgSO_4}$. The effect of pressure on $\mathrm{CO_2}$ solutions is anomalously large. Zisman $^{447}$ measured in my laboratory the electrical conductivity at 30 and 75° up to $11\,000\ \mathrm{kg/cm^2}$ of the following $0.01\,N$ solutions in water: $\mathrm{HCl}$, $\mathrm{LiCl}$, $\mathrm{NaCl}$, $\mathrm{KCl}$, $\mathrm{RbCl}$, $\mathrm{CsCl}$, $\mathrm{NaF}$, $\mathrm{NaBr}$, $\mathrm{NaJ}$, $\mathrm{Na_2SO_4}$, $\mathrm{Na_2C_2H_3O_2}$, $\mathrm{CaCl_2}$, $\mathrm{ThCl_4}$, $\mathrm{BaCl_2}$, $\mathrm{K_3Fe(CN)_6}$, and $\mathrm{K_4Fe(CN)_6}$.

In many cases the electrical conductivity has a flat maximum with respect to pressure at low pressures; between 3000 and $8000\ \mathrm{kg/cm^2}$ the electrical conductivity in almost all cases decreases linearly with increasing pressure and at the same rate for all solutions. The behavior of $\mathrm{KCl}$ is exceptional. The maximum of electrical conductivity cannot always be explained by a change in the degree of dissociation with pressure. The Debye–Hückel equation requires a large change in ionic diameter with pressure. Edler and Zeier $^{448}$ measured the electrical conductivity at 200 atm of pure transformer oil. Ohm’s law is not obeyed; the increase in pressure does not affect the deviations from Ohm’s law. In a constant field the current decreases exponentially with increasing pressure.

Fisher $^{449}$ gave a review of works with fifteen references. Jost and Nelep $^{450}$ published theoretical calculations of the energy of disordering and swelling and also discussed the effect of pressure on the conductivity of electrolytes.

CITED LITERATURE

G. Tammann and W. Tofaut, Zschr. f. anorg. Chemie 182, 353 (1929). Effect of pressure on the conductivity of acid solutions.
G. Tammann and A. Rohmann, Zschr. f. anorg. allgem. Chemie 183, 1 (1930). Effect of pressure on the electrical conductivity of salt solutions.
L. H. Adams and R. E. Hall, J. Phys. Chem. 35, 2145 (1931). Effect of pressure on the electrical conductivity of solutions of sodium chloride and other electrolytes.
A. M. Monoszon and V. A. Pleskov, Zhurn. fiz. khim. 3, 236 (1932), physicochemical properties of solutions in compressed gases. IV. Electrical conductivity of solutions of alkali-metal nitrates in liquid ammonia under pressure.
Einar Brander, Soc. Sci. Fenn. Comm. Phys. Math. 6, No. 8, 1 (1932). Effect of pressure on the conductivity of electrolytes.
W. A. Zisman, Phys. Rev. 39, 151 (1932). Effect of pressure on the electrical conductivity of aqueous solutions of salts.
H. Edler and O. Zeiger, Zschr. f. Physik 84, 356 (1933). Conductivity of liquid dielectrics at high pressure.
P. Z. Fisher, Izv. Inst. khim. Akad. Nauk USSR 2, 303 (1935). Effect of pressure on the electrical conductivity of solutions.
W. Jost and G. Nelep, Zschr. f. physik. Chemie 32, 1 (1936). Theory of the electrolytic conductivity and diffusion in crystals. III. Calculation of the energies for the disruption of order and swelling. Effect of pressure on electrolytic conductivity.

3. EFFECT OF PRESSURE ON THE DIELECTRIC CONSTANT

The largest number of works in this field was carried out by the laboratories of Michels and Keyes.

A. Michels and C. Michels $^{451}$ measured the dielectric constant of nitrogen up to $150\ atm$ at 25, 75 and 125°, with the exception of 1 and $25\ atm$, where the measurements were not very accurate; they found that the Clausius–Mossotti expression $(\varepsilon-1)(\varepsilon+2)(1/d)$ is constant. The same authors $^{452}$ measured the dielectric constant of carbon dioxide up to $1000\ atm$ between 25 and $150^\circ\mathrm{C}$; these limits include the critical region and extend somewhat above and below it. The Clausius–Mossotti expression is independent of temperature and has a tendency to decrease with increasing pressure.

Michels, Jaspers and Sanders $^{453}$ measured the dielectric constant of nitrogen up to $1000\ atm$ between 25 and 100°. Within this range the Clausius–Mossotti expression is quite constant. Michels, Sanders and Schipper $^{454}$ measured the dielectric constant of hydrogen up to $1425\ atm$ between 25 and 100°; the Clausius–Mossotti expression is constant within the limits of experimental error.

Michels and Kleerekoper $^{455}$ measured the dielectric constant of carbon dioxide at 25, 50 and 100° up to $1700\ atm$. This was a partial repetition of earlier measurements, with the special aim of increasing the accuracy in the region of small densities. It was found that the Clausius–Mossotti expression has a clearly pronounced maximum at pressures below $300\ atm$, the total change of the expression being of the order of 2%; the maximum at 50° is sharp, and at 100° rounded.

Keyes and Kirkwood $^{456}$ measured the dielectric constant of carbon dioxide at 0, 35, 70 and 100° up to $200\ atm$. The Clausius–Mossotti expression is independent of temperature, but depends on density, increasing asymptotically at high densities.

Keyes and Kirkwood $^{457}$ measured the dielectric constant of ammonia at 100, 125, 150 and 175° up to $100\ atm$. The Clausius–Mossotti expression is far from constant, increasing with increasing pressure and decreasing with increasing temperature; the largest deviations correspond to values from 36.49 to 43.05.

Ylig, Kirkwood and Keyes $^{458}$ repeated and extended the previous measurements with carbon dioxide and ammonia and supplemented them for methane, hydrogen and nitrogen. The limits were extended from 0 to 200° and up to $250\ atm$. The Clausius–Mossotti expression does not depend on density for methane, hydrogen and nitrogen; it increases slowly with density for carbon dioxide and more rapidly for ammonia. The molar polarization $P_0$ is independent of temperature for all the substances investigated, with the exception of ammonia, which indicates the absence of a permanent dipole moment. $P_0$ for ammonia increases with temperature; the permanent dipole moment, calculated by extrapolation,

by its temperature variation agrees with that observed by other investigators.

Keyes and Oncley $^{459}$ gave an extensive literature review on the dielectric constant of compressed gases. They come to the conclusion that the Clausius–Mossotti expression does not depend on density and temperature for helium, hydrogen, and nitrogen, and is a function of density for carbon dioxide, methane, and propane.

The next four papers likewise concern the influence of pressure on the dielectric constant of gases. Brockson $^{460}$ measured the dielectric constant of air up to $170\ \mathit{atm}$; he found that it varies with pressure almost linearly.

In a second paper Brockson $^{461}$ gives data for commercial nitrogen within the same limits. $\varepsilon - 1$ varies linearly with pressure at a rate of $556 \cdot 10^{-6}$ per atmosphere at $16^\circ.5$. Macnabney, Moulton, and Boymlin $^{462}$ determined the dielectric constant of air and hydrogen at $20^\circ$ between 72 and $335\ \mathit{atm}$. For air the Clausius–Mossotti expression is probably constant within the limits of experimental error; for hydrogen it decreases uniformly with increasing pressure from 1.16 to 0.99.

Kubo $^{463}$ gave a carefully developed theory of the effect of pressure on gases on the basis of Debye’s polarization theory, the special feature being the method of integration over all orientations for both polar and nonpolar molecules. Satisfactory agreement was obtained with the experimental data of Keyes and Kirkwood, and also of Michels.

The remaining papers relating to this field concern the dielectric constant of liquids. Apparently, during this period no measurements were made on solids, for which the experimental difficulties are evidently considerably greater than in the case of gases and liquids.

Trendelenburg $^{464}$ proposed a method for measuring rapidly varying pressures by measuring, with an oscillograph, changes in the capacitance of a capacitor filled with a liquid. Benzene was proposed as a suitable liquid, and the paper contains data on the measurement of the dielectric constant of benzene as a function of pressure up to $200\ \mathit{atm}$. Noticeable deviations from linearity were found. An explanation is given of the application of this method up to $300\ \mathit{atm}$. Danforth $^{465}$, in my laboratory, measured the dielectric constant at several temperatures between 0 and $75^\circ$ up to $12{,}000\ \mathit{kg}/\mathit{cm}^{2}$ for the following ten liquids: carbon disulfide, ethyl ether, $n$-pentane, chlorobenzene, bromobenzene, hexyl alcohol, ethyl alcohol, $n$-butyl alcohol, glycerin, and eugenol. The measurements were performed at sonic frequency and at 247,000 cycles. At the high frequency a noticeable decrease in the dielectric constant at high pressures was observed for liquid glycerin, $i$-butyl alcohol, and eugenol. These are precisely the three liquids in which

pressure causes the greatest increase in viscosity. The obvious explanation of the abnormal dispersion is the suppression of the ability of the molecules to rotate sufficiently rapidly following the field because of the excessively high viscosity.

There is no trace of an anomaly at acoustic frequencies, which proves that this effect is not caused by freezing. The dielectric constant has the same course also in the region of pressures above 3000 atm as that found earlier by Karolus in the last pressure interval. The Clausius–Mossotti expression, in general, decreases with increasing pressure. Danforth found, however, that a simplification is introduced if the reciprocal Clausius–Mossotti expression is plotted as a function of density instead of pressure. The data of the majority of liquids plotted in this way fall almost on a straight line. The results lead one to suppose the necessity of a change in the polarizability of the molecules under pressure and in the “internal-field constant,” which is usually taken equal to $4\pi/3$. These two effects cannot be separated on the basis of the influence of pressure on the dielectric constant; other data are required.

In 1934 Chang $^{468}$ published the results of measurements of the dielectric constant of liquids up to $12000\ \mathrm{kg}/\mathrm{cm}^2$, which he had made in my laboratory several years earlier. This work is briefly described in my book, and since it was carried out before Danforth’s work, no further explanation is required. Scott $^{467}$, at the Bureau of Standards, measured, up to 700 atm, the dielectric constant, power factor, and electrical conductivity at 1000 cycles for a large number of sulfur–rubber compounds containing up to $32\%$ sulfur. The effect of pressure changed noticeably depending on the sulfur content; each of these three properties has a maximum with increasing sulfur content, and under pressure this maximum shifts toward a lower sulfur content. Up to $7.5\%$ S the dielectric constant increases slightly with pressure and decreases at higher contents. The power factor is independent of pressure up to $2\%$ sulfur, increases with pressure between 2 and $12\%$ S, and decreases with further increase in sulfur content.

In the interval from 12 to $19\%$ sulfur the electrical conductivity increases with pressure; outside this interval it decreases with pressure.

Bancroft $^{468}$ in my laboratory measured the influence of pressure up to $10000\ \mathrm{kg}/\mathrm{cm}^2$ on the permittivity of Rochelle salt within the temperature range from $-20$ to $60^\circ$. At atmospheric pressure it is well known that Rochelle salt has a lower critical temperature of $-18^\circ$ and an upper critical point at $23^\circ.7$; between these two temperatures the dielectric constant has an infinitely large value, and the behavior of the salt is an electrical analogue of ferromagnetic substances.

Bancroft found that both critical temperatures increase with pressure approximately linearly; the upper one rises by $10^\circ.73$

and lower by 3°.77 at 1000 kg/cm². Complete curves are given in the form of the reciprocal permeability as a function of pressure, at every 10° C both for the ferromagnetic region and for the normal regions on each side. On the basis of modern theory, it is apparently impossible to give a simple explanation.

Owen and Brinkley⁴⁶⁹ published a theoretical paper on the effect of pressure on a liquid, in which they found that the dielectric constant satisfies an equation of exactly the same form as Tait’s equation for density, already discussed in connection with Gibson’s work, the constants in the logarithmic part being the same for both equations. This equation reproduces the experimental data of Frank, Kiropulos, and Danforth.

Böttcher⁴⁷⁰ considered the effect of pressure on molecular polarization in nonpolar gases and liquids. A modified form of the Clausius–Mossotti expression was derived, including the effect of molecular polarization and molecular radius. This equation reproduces Danforth’s data for CS₂ up to 12,000 kg/cm².

The equation requires that molecular polarization, with increasing pressure, pass through a maximum. There is experimental confirmation of this in the case of CS₂ and CO₂.

CITED LITERATURE

A. Michels and C. Michels, Phil. Mag. 13, 1192 (1932). Dielectric constant of nitrogen up to 150 atm at 25, 75, and 125° C.
A. Michels and C. Michels, Phil. Trans. Roy. Soc. London 231, 409 (1933). Effect of pressure on the dielectric constant of carbon dioxide up to 1000 atm between 25 and 150° C.
A. Michels, A. Jaspers, and P. Sanders, Physica 1, 627 (1934). Dielectric constant of nitrogen up to 1000 atm at temperatures from 25 to 150° C.
A. Michels, P. Sanders, and A. Schipper, Physica 2, 753 (1935). Dielectric constant of hydrogen at pressures up to 1425 atm and temperatures of 25 and 100° C.
A. Michels and L. Kleerekoper, Physica 6, 586 (1939). Dielectric constant of CO₂ at 25, 50, and 100° C up to 1700 atm.
F. G. Keyes and J. G. Kirkwood, Phys. Rev. 36, 754 (1930). Dielectric constant of carbon dioxide as a function of temperature and density.
F. G. Keyes and J. G. Kirkwood, Phys. Rev. 36, 1570 (1930). Dielectric constant of ammonia as a function of temperature and density.
H. H. Uhlig, J. G. Kirkwood, and F. G. Keyes, J. Chem. Phys. 1, 155 (1933). Dependence of the dielectric constant of gases on temperature and density.
F. G. Keyes and J. L. Oncley, Chem. Rev. 19, 195 (1936). Relation between the dielectric constants of certain compressed gases and density.
J. W. Broxon, Phys. Rev. 37, 1388 (1931). Dielectric constant of air at high pressure.
J. W. Broxon, Phys. Rev. 38, 2049 (1931). Dielectric constant of industrial nitrogen at high pressures.

R. McNabney, W. Moulton and W. L. Beuschlein, Phys. Rev. 47, 695 (1935). Dielectric constants of air and hydrogen at high pressures.
M. Kubo, Bull. Chem. Soc. Japan 13, 167 (1938). Dielectric constant of gases at high pressure.
F. Trendelenburg, Zschr. f. techn. Physik 11, 465 (1930). Investigation of the effect of pressure on liquids by measuring the dielectric constant with pressure.
W. E. Danforth, Jr., Phys. Rev. 35, 1224 (1931). Dielectric constants of liquids at high pressures.
Z. T. Chang, Chinese J. Phys. 1, No. 2, 1 (1934). Dielectric constant of liquids at high pressure.
A. H. Scott, J. Research Nat. Bur. Stand. 15, 12 (1935). Effect of pressure on the dielectric constant, power factor, and breakdown strength of vulcanized rubber.
D. Bancroft, Phys. Rev. 53, 567 (1938). Effect of hydrostatic pressure on the permeability of Rochelle salt.
B. B. Owen and S. R. Brinkley, Jr., Phys. Rev. 64, 32 (1943). Effect of pressure on the dielectric constants of liquids.
C. J. F. Böttcher, Physica 9, 945 (1943). Dependence of the molecular polarization of nonpolar gases and liquids on pressure.

4. VARIOUS ELECTRICAL EFFECTS OF PRESSURE

Poulter, Richey, Wilson, and Fulton^471 in 1929 published a study of the effect of pressures up to 16,000 atm on the electromotive force of the Weston cell. This was followed in 1932 by a paper on the same question by Poulter and Richey^472, in which more precise experiments at pressures up to 12,000 kg/cm² were described. Two experimental procedures were used. According to one, used up to 8000 kg/cm², the cell is mounted in an open glass or wax vessel, the electrodes being introduced through the open top. According to the other procedure, which was used for the maximum pressures, the cell is mounted in a completely closed rubber container, the pressure being transmitted through its walls. The e.m.f. increases with pressure; the rate of increase for the first thousand atmospheres agrees with the results obtained earlier by Cohen and Zinninge. Above the first few thousand atmospheres, large deviations from linearity are observed in the direction of a decrease in the rate of increase.

The total change of the e.m.f. in the pressure range studied is from 1.018 to 1.074 volts. The authors understood that there are too many unknown factors here to attempt to predict thermodynamically the change of e.m.f. with pressure. Cohen and Zinninge obtained agreement between theory and experiment within the limits in which they worked; therefore at high pressures it is necessary to assume the presence of new, as yet unknown factors.

Skutta^473 measured the electrical resistance of nickel and iron tubes subjected to high internal pressure of hydrogen or nitrogen. The tubes were activated by preliminary heating to

red heat in hydrogen at a pressure exceeding the applied one. The resistance increased with pressure for the steel—hydrogen system and decreased for the nickel—hydrogen system.

With nitrogen, the resistance of both metals increases considerably.

Scouli and Kantorovich^474 compressed fifteen dry metal powders to 4000 atm, and found that the electrical resistance of a pressed specimen varies from 1.1 times this value for massive tin to a 400-fold increase for massive tungsten.

Bellin^475 found that the Hall coefficient increases when the pressure is raised to 50 atm; this is apparently the only investigation of this question.

Cassel and Crumbaugh^476 measured the influence of pressure up to ten atmospheres on the overvoltage in the electrolysis of water. Some of their data agree with the data of other investigators; other data are considerably larger.

Cohen and Pippenbroek^477 measured the influence of pressures up to 1550 kg/cm^2 on the emf of the concentration cell Te—amalgam (Te CNS—K CNS / KCl—TeCl) Tl—amalgam.

At atmospheric pressure the emf was 0.00856 volts, and at 1500 atm it increased to 0.01282 volts. The theoretical value, calculated thermodynamically, agrees with these data to within 0.75%, better than might have been expected if one takes into account the presence of errors in the thermal data. Shishkin and Karnaukh^478 found that the anodic and cathodic potentials of nickel electrodes used in the electrolysis of 0.5 N NaOH decrease slightly at a pressure of 100 atm. A similar, but somewhat smaller, effect was found on iron electrodes.

Sharavsky^479 investigated the influence of pressure up to 8000 kg/cm^2 on the properties of a cuprous-oxide rectifier. Rectification improved up to 4000–5000 atm. Above this pressure deterioration sets in. No change in the electrical conductivity of Cu₂O was detected up to a pressure of 8570 atm.

Michels, Michels-Ferart, and Bijl^480 processed some of their previous results for the dielectric constant of CO₂ and found that the Clausius–Mossotti expression decreases with increasing pressure and is approximately a single-valued function of pressure, but not of density. They believe that the polarizability of the molecule must be a function of pressure.

This article was followed by another theoretical article on the same question by Michels, de Boer, and Bijl^481, in which they use their experimental data up to 3000 atm.

Trey^482 found that the rectifying action associated with a layer adsorbed on the surface of a piece of compressed PbS powder disappears if this piece is subjected to a pressure above 4000 kg/cm^2. Birch^483 investigated small corrections associated with the action of

pressure on the thermoelectromotive force, when a thermocouple is introduced into a vessel that is under pressure.

Basset484 described experiments in which he succeeded in maintaining a voltaic arc between graphite electrodes in an atmosphere of nitrogen or argon at pressures up to 9000 kg/cm². It was necessary to pass a current of 10 amperes at a voltage of 600 volts. The crater was very small, and the rods burned away very quickly; the temperature of the crater was about 5000°. He also produced an arc between tungsten and tantalum electrodes under similar conditions.

CITED LITERATURE

T. C. Poulter, C. Ritchey, R. Wilson and J. Fulton, Proc. Yowa Acad. Sci. 36, 304 (1929). Effect of pressures up to 16 000 atm on the electromotive force of a Weston cell.
T. C. Poulter and C. Ritchey, Phys. Rev. 39, 816 (1932). Effect of pressure on the e.m.f. of a normal Weston cell.
T. Skutta, Zschr. f. Physik 65, 385 (1930). Electrical conductivity of steel and nickel at high gas pressure.
F. Skaupy and O. Kontorowich, Zschr. f. Elektrochemie 37, 482 (1931). Behavior of metallic powders under pressure.
F. Bellia, Nuovo Cimento 10, 221 (1933). Effect of pressure on galvanomagnetic phenomena.
H. M. Cassel and E. Krumbein, Zschr. f. physik. Chemie, A. 171, 70 (1934). Effect of pressure on the overvoltage in the electrolysis of water.
Ernst Cohen and K. Piepenbroek, Zschr. f. physik. Chemie, A. 170, 145 (1934). Effect of pressure on affinity. IV.
V. Shishkin and E. Karnaukh, Zschr. f. Elektrochemie, 42, 693 (1936). Effect of pressure on the electrode potentials in the electrolysis of water.
P. V. Sharavsky, Zhurn. tekhn. fiziki 6, 1531 (1936). Effect of high pressures on the properties of cuprous rectifiers.
A. Michels, C. Michels—Veraart and A. Bijl, Nature 130, 509 (1936). Indication of a decrease in the polarizability of nonpolar molecules with pressure.
A. Michels, J. de Boer and A. Bijl, Physica 4, 981 (1937). Remarks on molecular interaction and its influence on polarizability.
F. Trey, Physik. Zschr. 37, 213 (1936). Destruction of the adsorbed rectifying layer under pressure.
F. Birch, Rev. Sci. Inst. 10, 137 (1939). Measurements of high temperatures in an apparatus of high pressure by means of a thermocouple.
James Basset, Comptes rendus 214, 715 (1942). Electric arc in gases at very high pressures.

MAGNETIC EFFECTS AT HIGH PRESSURE

Comparatively few new works have been carried out in this field. Adams and Green485 investigated the effect of pressures up to 3600 atm on the temperature of the magnetic inversion point of steel containing 35% nickel, of pure iron, meteoritic iron, and magnetite. In the measurements the specimen was included as an arm of a transformer placed under ...

pressure in a vessel containing a small heating furnace. The investigators came to the conclusion that the influence of pressure on the inversion point of any of these metals is too small for it to be measured reliably; in the limiting case the temperature may decrease very slightly with increasing pressure. They indicated that the earth’s core is at a temperature considerably exceeding the temperature of possible magnetization.

Steinberger $^{486}$, in my laboratory, studied the influence of pressure on the magnetic-flux density for eleven iron–nickel alloys, at intervals of ten percent nickel, including the pure metals. The specimens were made in the form of armature rings, with primary and secondary windings. The influence of pressure was studied both from the change in the magnetic field at various constant pressures and from the change in pressure at a constant field. The effects were complex; linear, nonlinear, and hysteresis effects were observed. The application of pressure at a constant field usually caused a decrease of the flux, often a comparatively large one. An alloy with $30\%$ nickel became almost nonmagnetic under a pressure of $12\,000\ \mathrm{kg}/\mathrm{cm}^{2}$. Of the other alloys, pure iron gave the greatest change of flux, and the alloy with $90\%$ nickel the smallest.

Ebert and Cusman $^{487}$ studied the influence of a pressure of $300\ \mathrm{kg}/\mathrm{cm}^{2}$ at room temperature on magnetic permeability over a wide range of field strengths, but especially at saturation intensity. A ballistic method was used, with two apparatus designs for strong and weak fields. In the case of strong fields, a high-pressure vessel made of nonmagnetic beryllium bronze was placed along the axis of an electromagnet in such a way that it could be rapidly and completely removed from the field by longitudinal displacement along the axis of the electromagnet, while a geometrically similar specimen not subjected to pressure was simultaneously introduced into the field. Measurements were made on pure iron and nickel, on alloys of iron with nickel, cobalt, chromium, and platinum, on alloys of nickel with aluminum, chromium, cobalt, copper, and manganese, on alloys of platinum with manganese, and on ternary iron—cobalt—chromium systems. In general, the influence of pressure on magnetic saturation is very small and varies from $0.1$ to $0.01\%$ per $1000\ \mathrm{kg}/\mathrm{cm}^{2}$.

There are, however, certain alloys in the critical composition region for which this effect may be significantly greater, up to a decrease of $6.5\%$ per $1000\ \mathrm{kg}/\mathrm{cm}^{2}$. Such critical compositions are: $70\%$ Fe and $30\%$ Ni, $60\%$ Pt and $40\%$ Fe, and one of the Fe-Co-Cr compositions. Here, apparently, there is a connection between these large coefficients and the noticeable temperature hysteresis between the $\alpha$- and $\gamma$-phases.

Michels, Jasperse, de Boer, and Strijland $^{488}$ investigated the influence of pressures up to $2615\ \mathrm{atm}$ on the temperature of the Curie point for an alloy containing $70\%$ Ni and $30\%$ Cu. At atmospheric pressure the Curie region is smeared out between $10$ and $40^\circ\mathrm{C}$. The method consisted in measuring the elec-

tric resistance and determining how far the region of anomaly in the resistance is displaced with pressure. Since these phenomena are strongly smeared out, it is difficult to obtain precise results. The authors came to the conclusion that the anomaly is displaced in the direction which should correspond to a rise in the fictitiously selected Curie point by $6.5\cdot 10^{-5}$ degree per 1 atm. Ebert and Kusmann$^{489}$, in a second paper, investigated the effect of pressure up to $4000\ \text{kg}/\text{cm}^2$ on the Curie temperature in the temperature range from 100 to $200^\circ$ for seven different alloys: Ni—Cu, Ni—Al, Ni—Fe—Mn (4), and Co—Fe—Cr. The magnetization decreases with increasing pressure. The effect of pressure on magnetization increases with increasing temperature and decreases with increasing pressure up to the Curie point; the rates of change become more pronounced near this point. Extrapolation leads to the conclusion that the surface formed in the coordinates pressure—temperature—magnetization must approach a plane asymptotically, so that ferromagnetism cannot disappear at any finite pressure. This agrees with the assertion that pressure does not affect the Curie-point temperature, which, however, contradicts the data of other investigators. Leĭpunsky$^{490}$ published a theoretical paper in which, from the Clapeyron equation and Heisenberg’s theory of ferromagnetism, he calculated that the Curie point in nickel and iron should be shifted by pressure by a quite definite amount. He believes that the experiment simply has never been carried out under the necessary conditions. According to his calculations, the Curie point for iron or nickel inside the Earth lies between 2000 and $4250^\circ$, which should not exclude ferromagnetism of the Earth’s core.

Birch studied the effect of pressure up to $4000\ \text{kg}/\text{cm}^2$ on the $\alpha$—$\gamma$ transformation in iron. At atmospheric pressure it occurs at $900^\circ\text{C}$ with a decrease in volume, so that the transition line is shifted by pressure toward lower temperatures. The measurements were carried out by the method of thermal expansion, which made it possible to determine the pressure-induced shift of the temperature at which the volume—pressure curve breaks. The dependence on pressure is expressed by a straight line; the temperature is lowered by $8.5^\circ$ per $1000\ \text{kg}/\text{cm}^2$. It follows from this that the $\alpha$-phase plays a comparatively small role in the problem of terrestrial magnetism, since it disappears at the pressures occurring in the Earth’s crust.

Sleter$^{492}$ published a theoretical work in which he shows, applying the Clapeyron equation, that in iron–nickel alloys the initial effect of pressure on pure iron consists in raising the Curie temperature by $5\cdot 10^{-5}$ degree per atmosphere. This coefficient becomes smaller with increasing nickel content and should change sign at 70% nickel. The author is of the opinion that there is no plausible explanation of terrestrial magnetism from the point of view of ferromagnetism.

Michels and Strijland$^{493}$ determined the effect of a pressure of $2640\ \text{kg}/\text{cm}^2$ between 0 and $99^\circ$ on the electrical resistance of monel metal (Ni—68%, Cu—29%, Fe—1.64%, Mn—1.0%, Si—0.1%, C—0.15%)

and, having studied the displacement of the region of the resistance anomaly, came to the conclusion that the Curie temperature increases by $0.03^\circ$ per $1000\ atm$. In the pressure interval investigated, the pressure coefficient of resistance has an acuminate maximum.

References Cited

L. H. Adams and J. W. Green, Phil. Mag. 12, 361 (1931). The influence of hydrostatic pressure on the critical temperature of magnetization of iron and other substances.
R. L. Steinberger, Physica 4, 150 (1933). Magnetic properties of iron–nickel alloys under hydrostatic pressure.
H. Ebert and A. Kussmann, Physik. Zschr. 38, 437 (1937). Change in magnetic saturation.
A. Michels, A. Jaspers, J. de Boer, and J. Strijland, Physica 4, 1007 (1937). Influence of pressure on the Curie point for a 70–30% Ni—Cu alloy.
H. Ebert and A. Kussmann, Physik. Zschr. 39, 598 (1938). On the influence of hydrostatic pressure on the temperature of the Curie point.
O. I. Leipunsky, Zhurnal Eksperimental’noi i Teoreticheskoi Fiziki 8, 1026 (1938). Displacement of the Curie point under the action of pressure.
F. Birch, Am. J. Sci. 238, 192 (1940). Transformation of iron at high pressures and the problem of terrestrial magnetism.
J. C. Slater, Phys. Rev. 53, 54 (1940). Note on the effect of pressure on the Curie point of iron–nickel alloys.
A. Michels and J. Strijland, Physica 8, 53 (1941). Influence of pressure on the Curie point of monel metal.

Optical Effects of High Pressure

1. Influence of Pressure on the Refractive Index

Bennett $^{484}$ measured, by an interferometric method, the dispersion and refractive index of nitrogen for three wavelengths up to $7\ atm$. The Lorentz–Lorenz equation was observed, and the dispersion depended linearly on pressure. Poulter, Rich, and Benz $^{485}$ measured the refractive index of paraffin oil up to $13\,600\ atm$ and of glycerin up to $7200\ atm$. The apparatus consisted of a high-pressure vessel with two Poulter windows arranged at an angle of $30^\circ$ to one another, so that the space between them corresponds to a 30-degree prism. The refractive index of the medium filling the vessel was determined by the method of minimum deviations, using the usual formulas and without introducing a correction for the influence of pressure on the refractive index of the windows. It was found that the Lorentz–Lorenz equation is approximately constant for both liquids over the entire pressure range; small deviations from constancy of the Lorentz–Lorenz expression were unsystematic and did not exceed two parts in 300 for the oil and four parts in 300 for glycerin.

Pointexter and James^496 described apparatus, largely similar to Poulter’s, in which they measured, for three wavelengths, the influence of pressure up to 1440 atm on the refractive index of water. The Lorentz–Lorenz expression is not constant, but at the maximum pressure decreased by from 4 to 14 parts in 2000, the decrease being the greater the shorter the wavelength.

Pointexter and Rosen^498 investigated the influence of pressure up to 1800 kg/cm² on the refractive index of pure water, pure ethyl alcohol, and five intermediate solutions. The measurements were made with a liquid prism with an angle of 51°. The authors express the dependence of the refractive index on pressure by an equation with four constants. The behavior of the Lorentz–Lorenz expression is not discussed; the change in the refractive index of pure water in this pressure interval amounts to only one third of the corresponding relative change in density.

Pointexter^498, apparently with the same apparatus and in the same pressure interval, investigated the influence of pressure on the refractive index of carbon disulfide. The measurements were made for three wavelengths. The dispersion increases with pressure, but apparently not linearly, the rate of increase being greater at low pressures.

John^499, in Calcutta, published a theory of the influence of pressure on the refractive index and dielectric constant of carbon dioxide, and succeeded in bringing the theory into agreement with the experiments of Phillips and Michels and Michels.

Michels and Hamers^500 investigated the influence of pressure up to 2400 atm on the refractive index of CO₂ at 25, 32, 50, and 100° for six wavelengths between 4471 and 6678 Å. Detailed tables and graphs are given. The Lorentz–Lorenz expression is not constant, but decreases with increasing pressure by a maximum of 2.3%.

Gibson and Kincaid^501 measured, up to 1250 bar and from 25 to 65°, the volume and refractive index of benzene. The refractive index was measured by a new method, in which the pressure of disappearance of the outlines of optical glasses with different refractive indices immersed in the liquid is recorded. The correction for the change in the refractive index of the glass under pressure amounts to only 2.5%. The Lorentz–Lorenz expression $[(n^2 - 1)/(n^2 + 2)]\cdot[1/d] = \mathrm{const.}$ deviates strongly from constancy in one direction, while the Gladstone and Dale expression $(n - 1)/d = \mathrm{const.}$ deviates in the other. The purely empirical Eykman formula $[(n^2 - 1)/(n + 0.4)]\cdot[1/d] = \mathrm{const.}$ represents the data within the experimental error. The dispersion, i.e. $n_{589} - n_{486}$, increases by 7% per 1000 bar. Hayden^502, under Pointexter’s direction and using his apparatus, in 1938 measured the refractive index and dispersion of glycerin for three wavelengths up to 2500 atm. The dispersion proved to be a linear function of pressure and increased with increasing pressure. The Lorentz–Lorenz expression was confirmed.

References Cited

C. E. Bennett, Phys. Rev. 37, 263 (1931). Dispersion and refractive index of nitrogen as functions of pressure, measured by the interferometric displacement method.
T. C. Poulter, C. Ritchey and C. A. Benz, Phys. Rev. 41, 366 (1932). Effect of pressure on the refractive index of paraffin oil and glycerin.
F. E. Poindexter and L. E. James, Phys. Rev. 42, 910 (1932). High-pressure refractometer.
F. E. Poindexter and J. S. Rosen, Phys. Rev. 45, 760 (1934). Effect of pressure on the refractive index of aqueous solutions of ethyl alcohol.
F. E. Poindexter, Phys. Rev. 47, 202 (1935). Effect of pressure on the refractive index of carbon disulfide.
P. O. John, Phil. Mag. 22, 274 (1936). Refractive index and dielectric constant of carbon dioxide at high pressures.
A. Michels and J. Hamers, Physica 4, 995 (1937). Effect of pressure on the refractive index of CO₂.
R. E. Gipson and J. F. Kincaid, J. Am. Chem. Soc. 60, 511 (1938). Effect of temperature and pressure on the volume and refractive index of benzene.
C. K. Hayden, Univ. Microfilms, Ann Arbor, Michigan, No. 173 (1940). Effect of high pressure on the refractive index and scattering power of glycerin.

2. Photographic Processes at High Pressure

Most of the works concern the effect of “pressure,” which is not hydrostatic pressure but simply compressive stress. There is undoubtedly some connection between the effect of the two kinds of stress, and I considered it necessary to note all these works. Unless otherwise specified, “pressure” should be understood to mean simple compression.

Schwarz and Urbach^503 published a paper on the photochemistry of alkali-metal halides and elementary photographic processes, which I have seen only in abstract. It states that a pressure of 100–200 kg/cm² produces a noticeable effect, but no details are given.

Maring^504 studied the effect of pressure on the formation of the latent image and on the reversal process in the region of solarization. Pressure decreases the density of the image, and this decrease is greater the higher the pressure and smaller the greater the exposure. The density of the image depends linearly neither on pressure nor on exposure. In the region of solarization, pressure gives a noticeable acceleration of reversal.

Ni and Tsen^505 found that pressure always decreases sensitivity both in the region of normal exposures and at large overexposures. The effect of pressure decreases with increasing

wavelength and varies over a wide range depending on the nature of the film. Ni and Lu^506 described an apparatus for applying pressure to a plate—a strong quartz plate pressed against the photographic plate by a special lever—and a method for measuring sensitivity. Rirdon^507 studied the effect of pressures up to $1375\ \mathrm{kg/cm^2}$, depending on the method of development; pressure reduces the density of the image for all methods of development. The decrease ranges from 13 to 68%, depending on the method of development.

Poindexter, Rirdon, and Defoe^508 described a “new” photographic effect produced by pressure. After exposure and before development the film was subjected to hydrostatic pressure in water at $2500\ \mathrm{kg/cm^2}$ for 20 to 30 minutes. The density of the developed image decreases by 4–5% for an image density of about 0.7.

Ni^509 found that pressure lowers the density of the image, and that this effect increases with the wavelength of the incident light, while the relative decrease does not depend on the absolute value of the density.

Jacobs^236,287, in two papers already mentioned above in connection with polymorphic transitions, incidentally describes the behavior of a photographic film under hydrostatic pressure of helium at $5000\ \mathrm{kg/cm^2}$ under the action of X-rays. The influence of pressure on sensitivity, if it existed at all, was no more than 10–15%. In order not to damage the film mechanically during the application and removal of pressure, special precautions were taken. After the application of pressure the film is stretched by 2%. This makes it necessary to use certain wavelengths.

Rirdon^510 described experiments in which the film is subjected to simple compression by a glass block during exposure. In all cases pressure decreases the density of the image, and this decrease depends on the exposure and the methods of development. Lu, Chang, and Lu^511 investigated the effect of pressure on the sensitivity of film to X-rays. It was already known that pressure decreases sensitivity to visible light but increases it with respect to $\gamma$-radiation. Simple compressive stresses from 110 to $1180\ \mathrm{kg/cm^2}$ were applied. The sign of the pressure effect for X-rays depends on the type of plate. Sensitivity falls for Kodak and Agfa plates and increases for Ilford plates. There are probably two different mechanisms here—one for visible light and another for $\gamma$-rays; X-rays excite both reactions, but the predominance of one mechanism or the other depends on the type of plate.

Lu, Chang, and Lu^512 gave a systematic description of the effect of pressure up to 140 atm. Chung^513 compressed with nitrogen up to 140 atm. He observed varied but not sharply expressed effects, the same for violet and yellow colors.

CITED LITERATURE

G. Schwarz and F. Urbach, Phot. Korr. 61 (1932). Photochemistry of alkali-metal halides and the elementary photographic process.
Karl A. Maring, Phys. Rev. 42, 911 (1932). The influence of pressure on the formation of the latent photographic image, especially its influence on reversal in the region of solarization.
Tsi-Ze Ny and Long-Chao Tsien, Chinese J. Phys. 1, 66 (1934). Influence of pressure on photographic sensitivity.
Tsi-Ze-Ny and Ta-Juan Lu, J. Opt. Soc. Am. 26, 26 (1936). Influence of pressure on photographic sensitivity.
Anna Joyce Rearden, Phys. Rev. 49, 413 (1936). The influence of pressure and physical development (and a decrease in the density of the latent image).
F. E. Poindexter, A. J. Rearden and O. K. DeFos, Phys. Rev. 49, 414 (1936). A new effect of pressure in photography.
Tsi-Ze Ny, 9-th Congr. Intern. Photo, Paris 83 (1935). Influence of pressure on photographic sensitivity.
A. J. Rearden, J. Opt. Soc. Am. 29, 427 (1939). Influence of pressure on the solarized latent photographic image.
S. S. Lu, Chang Hung-Chia and Lu Ta-Juan, Comptes rendus 208, 1296 (1939). Influence of pressure on the sensitivity of photographic plates to X-rays.
S. S. Lu, Chang Hung-Chia, Lu Ta-Juan, Chinese J. Phys. 4, 55 (1940). Photographic effects caused by pressure.
Choong Shin-Piaw, J. Opt. Soc. Am. 31, 186 (1941). Influence of pneumatic pressure on photographic sensitivity.

3. VARIOUS OPTICAL EFFECTS AT HIGH PRESSURE

Przibram^514 investigated the piezochromatism of natural minerals. Various mineral powders were pressed at $20\,000\ \mathrm{kg/cm^2}$, and the change in color was studied. Yellow and red fluorite changed their color little, but green and blue fluorite became violet, and light-green fluorite became blue-green. Barytes and tourmalines did not change color. Yellow calcite became light gray with a bluish tint—a color not found in natural calcite. The color changes depend little on particle size. The change in color is attributed to deformation of the lattice and to complete or partial neutralization of free ions by electrons released by the photoeffect.

Poulter and MacComb^515 observed, through glass windows, the phosphorescence of a ZnS screen under pressures up to $30\,000\ \mathrm{atm}$ and found that the intensity of the phosphorescence decreases by one half.

No decrease was observed in the number of scintillations emitted by the screen under the action of radioactive substances placed in a high-pressure vessel.

Bhagavantam^516 found that discrete lines in the Raman spectrum of gases disappear above a certain pressure. Calculations give results that are in approximate agreement with experiment.

The calculated values of the pressure range from 450 atm for hydrogen to 5 atm for carbon dioxide; in all, nine gases were investigated.

Eizeman and Harris^517,518 from Keyes’s laboratory published two papers on the absorption spectra of argon, methane, and carbon dioxide at high pressures and low temperatures. At pressures reaching a maximum of 400 atm, no absorption whatever was found, either in the gaseous or in the liquid phases, for wavelengths from 2130 to 6780 Å. The positive results that they had previously obtained for carbon dioxide could not be reproduced and were attributed to the presence of some unknown impurities.

These results contradict the investigations of Garig, who, as the authors believe, made an error.

Kohn^519 described various attempts, mostly unsuccessful, begun in my laboratory, to carry out an investigation by means of x-rays under pressure. The x-rays were introduced into a high-pressure vessel through a beryllium window and were let out through a glass window arranged in such a way as to obtain a large angle. The pressure was brought up to 3000 atm. The experimental technique was later improved by Jacobson^236,237.

Grut and Bol^520,521 studied the emission and absorption spectra of mercury vapor at pressures up to 300 atm. They observed a bright continuous spectrum from ultraviolet to infrared light. The superposed spectral lines became blurred and shifted toward the red end. To determine the pressure, after careful calibration, optical absorption was used instead of manometers.

Cinzer^520,523 used apparatus with Poulter windows to study the influence of pressure on the optical absorption of water and the rotation of a sugar solution. For the absorption of water under pressure no satisfactory data were obtained because of disturbances caused by deformation of the window under pressure. The optical rotation of the sugar solution decreases with pressure; the decrease is linear up to 200 atm and then slows down. Pressure causes a strong inversion of the sugar solution. If the pressure over the sugar solution is maintained for several hours at 200 atm and then reduced, the rotation decreases greatly, and the sugar does not crystallize from the solution upon evaporation, but forms a gel.

Gibson and Loeffler^524 investigated the influence of pressure up to 1500 bar between 25 and 85° on the optical absorption of solutions of aniline, dimethylaniline, diphenylamine, and triphenylamine in nitrobenzene and a number of similar solutions. The apparatus was the same as that used in the investigation of the effect of pressure on the refractive index. With increasing pressure, the absorption shifted noticeably toward longer wavelengths; the same occurred with increasing temperature at constant volume; but a shift in either direction could be caused by an increase in

temperature at constant pressure. The authors consider that this effect cannot be attributed to the formation of compounds in solution, but that it occurs as a result of mutual polarization of molecules of different kinds.

Deych^525 compressed Rochelle-salt powder from 560 to 11,300 kg/cm² and then took Laue diagrams. The pressed powder had a density equal to only 80% of the density of the single crystal. The interference patterns and asterisms were very weak.

Kuss and Stuart^526 determined the Kerr constant for nitrogen, carbon dioxide, methane, and ethylene for pressures up to 400 atm. For carbon dioxide this constant changes smoothly in passing through the critical point. The results were explained from the standpoint of short-range and long-range order. At high pressures, apparently, short-range order is represented to a significant degree.

Bodolev and Leifutskii^527 found that under a pressure of 2500 atm at 25° the rate of mutarotation of glucose is 3.4 times greater than at atmospheric pressure. The activation energy is 14.5 cal instead of 17.5 cal.

Zander^528 investigated the influence of pressures up to 600 atm on the inversion of sucrose and the mutarotation of glucose. The rate of inversion does not change with pressure, but the rate of mutarotation increases.

CITED LITERATURE

Karl Przibram, Sitz. Ber. Preuss. Akad. Wien, IIA, 138, 263 (1929). Piezochromism in natural minerals.
T. S. Poulter a. M. C. Comb, Yowa Acad. Sci. 37, 311 (1939). Study of phosphorescent screens of zinc sulfide and radioactivity at ultrahigh pressures.
S. Bhagavantam, Nature 128, 188 (1931). Effect of pressure on the Raman spectrum.
B. J. Eisenman, Jr. a. L. Harris, J. Am. Chem. Soc. 54, 1778 (1932). Absorption spectra at high pressures and low temperatures. Transparency of argon and methane.
B. J. Eisenman, Jr. a. L. Harris, J. Am. Chem. Soc. 54, 1782 (1932). Absorption spectra at high pressure and low temperatures. Liquid carbon dioxide.
W. M. Cohn, Phys. Rev. 44, 326 (1933). X-ray investigations at high pressures.
W. de Groot, Verh. op 25 Mei 1935 aangeboden Prof. Dr. P. Zeeman, 312. Emission and absorption spectra of mercury at very high pressures (up to 300 atm).
W. de Groot a. C. Bol (see footnote 520).
R. H. Zinser, Phys. Rev. 50, 1097 (1936). Effect of pressure on the absorption and optical activity of water.
R. H. Zinser, Trans. Kan. Acad. Sci. 41, 241 (1938). Effect of hydrostatic pressure on polarization in an optical system.
R. E. Gibson a. O. H. Loeffler, J. Am. Chem. Soc. 62, 1324 (1940). Effect of pressure, temperature, and chemical composition on light absorption by mixtures of aromatic amines.

Karl Deutsch, Zschr. f. techn. Physik 21, 134 (1940). X-ray diffraction patterns of Seignette salt at high pressure.
E. Kuss u. H. A. Stuart, Physik. Zschr. 423, 95 (1941). Kerr effect and the state of order in strongly compressed gases and liquids.
V. K. Bodolev and O. I. Leipunsky, Zhurn. fiz. khimii 15, 1104 (1941). Mutarotation of glucose under pressure.
F. V. Sander, J. Biol. Chem. 148, 311 (1943). Effect of high pressure on the inversion of sucrose and the mutarotation of glucose.

EFFECT OF PRESSURE ON CHEMICAL REACTIONS

We do not attempt to classify the effect of pressure on various chemical phenomena. In most studies the displacement of chemical equilibrium or the change in the rate of reaction was investigated; these are so closely connected that they cannot usefully be separated from one another.

The papers reviewed relate chiefly to gas reactions having industrial applications. They will be discussed only briefly. The presentation is chronological.

Komatsu and Masumoto ^529 studied the catalytic hydrogenation of esters up to 100 atm. Komatsu and Hagiwara ^530 investigated the catalytic action of reduced copper on phenols at pressures up to 122 atm and 220°. Hugel and Cohn ^531 investigated the effect of temperatures up to 300° and pressures up to 1000 kg/cm² on hydrocarbons whose decomposition temperature is below their critical temperature, and also on hydrocarbons that decompose at a temperature above the critical one. Gillespie and Beattie ^532 published a theoretical paper in which they correlated known data on the synthesis of ammonia from 352 to 952° and 1000 atm with data on the compressibility and heat capacity of pure gases by means of the mass-action equation, which contains only two arbitrary constants. Nhegowan ^533, in a theoretical article, applies the van der Waals equation to the Haber–Bosch process of ammonia synthesis up to pressures of 1000 atm, where the yield of NH₃ is greater than the calculated one. Ipatieff and Muromtsev ^534 investigated the displacement of metals and their oxides from solutions of their salts by hydrogen at 300° and 250 atm. This article is devoted specifically to metal nitrates. In a second article, Ipatieff, Razuvaev, and Malinovsky ^535 considered, under the same conditions, specifically the displacement of arsenic from its salts by hydrogen. Morgan ^536 and co-workers discussed the industrial application of catalytic reactions under high pressure, with consideration of the latest theories.

Bohn ^537 published a review devoted to gas reactions at high pressures.

Komatsu and Mitsui ^538 studied the catalytic hydrogenation of benzoic acid at 225° and 92 atm.

Tanaka and Amatatsu ^539 studied the catalytic hydrogenation of safrole at 100 atm.

Lyon and Eyring⁵⁴⁰ investigated the reaction $N_2O_5 \rightleftarrows N_2O_4 + 1/2 O_2$, dissolving $N_2O_5$ and $N_2O_4$ in $CCl_4$ and subjecting the solution to a pressure of gaseous oxygen up to 1000 atm. The reaction proceeds completely to the right. The value of $\Delta H$, according to their experiments, does not exceed 1600 cal, as against the value 2690 cal reported in the literature.

Adkins, Kramer, and Connor⁵⁴¹ studied the rate of hydrogenation of five organic compounds on a nickel catalyst at pressures between 27 and 350 atm. Acetoacetic ester is hydrogenated at 30 atm, but the reaction rate increases considerably at high pressure, especially between 120 and 350 atm. Dehydroacetic acid is reduced at 149 atm twice as fast as at 108 atm, and more than four times as fast at 323 atm. Aniline does not react at all at pressures of the order of 30 atm. When the pressure is raised, the reaction proceeds, but its rate is insufficient for industrial use. The reduction of phenol and benzene proceeds well at 30–40 atm, but is appreciably accelerated when the pressure is raised to 330 atm.

Morgan⁵⁴² published a review article on organic syntheses carried out under pressure and gave many references to patents.

Tammann and Peip⁵⁴³ studied the effect of pressure up to 3000 kg/cm² at temperatures from 0 to 400° on the polymerization of styrene, isoprene, vinyl acetate, dimethylbutylene, and indene. At high pressures polymerization begins at lower temperatures. The rate of the process obeys the equation of a monomolecular reaction. They suggested that polymerization is caused by certain changes in the individual molecules.

Ipatiev and Tikhomirov⁵⁴⁴ studied the displacement of antimony by hydrogen from solutions of its salts at pressures up to 150 atm. Up to this pressure the rate is proportional to the pressure. This is a first-order reaction.

Ipatiev, Platonova, and Malinovskii⁵⁴⁵ carried out the same work for the displacement of arsenic by hydrogen from solutions of its salts. Up to 150 atm the amount of arsenic liberated is proportional to the pressure, and up to 250 atm, for solutions not stronger than 1 N, the reaction proceeds according to the first order. Ipatiev, Molzhentin, and Teodorovich⁵⁴⁶ carried out a similar investigation for the displacement of bismuth. The rate of displacement changes markedly, depending on the metal. In order to displace 1% of bismuth by hydrogen at 100 atm from a 1 N solution of $BiCl_3$, 37 years are required; under the same conditions 1% of antimony from an N solution of $SbCl_3$ will be displaced in 160 years, while the displacement of 1% of arsenic from an N solution of $AsCl_3$ will require 1440 years. A summary article was published by Ipatiev and Teodorovich⁵⁴⁷. The difference in the potentials of these three metals in solution is no more than 0.02 volt.

Tammann and Ruenbeck⁵⁴⁸ studied the behavior of several carbon compounds when heated to 650° at constant volume and an initial pressure of 1000 kg/cm². For a series of substances the rate of pressure increase with temperature was constant up to 400–500°, and above this

a much greater increase in pressure due to decomposition was observed.

Brown and Souder^549 and Brown, Souder, and Smith^550 described a high-pressure apparatus for studying the properties of paraffin hydrocarbons. Leon and Wint^551 investigated the effect of pressure up to 150 atm on the saccharification of cellulose with sulfuric acid before and after boiling. Pressure had no effect on the preboiled material. The unboiled material, which formed 30.4% glucose at atmospheric pressure, gave 36.5% glucose at 150 atm. Warren^552 investigated the influence of pressure on the pyrolysis of methane. He passed methane through a quartz tube at temperatures from 900° to 1120° and at pressures up to 104 atm, at various rates of gas passage. Increasing the pressure to 10 atm decreases the yield of unsaturated hydrocarbons, but has little effect on the yield of hydrogen, which decreases at higher pressures. Hugel and Kohn^553 carried out 22 experiments on the decomposition of hexadecene at 300—400° and pressures up to 1000 kg/cm². Hugel and Fries^554 studied the hydrogenation of several coal-tar derivatives at high pressures and temperatures. The results were complex in character; at higher temperatures cracking occurred. Conant and Peterson^555 published the final article in a series of works on polymerization under high pressure; the two preceding papers in this series—by Bridgman and Conant, and by Conant and Tongberg—were cited in my book. In this paper they specifically studied the mechanism of the reaction. They now believe that the presence of oxygen is always necessary for polymerization, changing the opinion expressed in one of their earlier papers. The role of pressure in accelerating polymerization consists in the fact that pressure orients the molecules and bundles, whereby chain reactions with long chains become possible.

They report a new substance capable of polymerization—cyclohexene oxide. The reaction proceeds very slowly. Attempts to stabilize the polymer of the aldehyde, which is formed under pressure and depolymerizes when the pressure is released, proved unsuccessful. The new experiments, as usual, were carried out in the range up to 12,000 kg/cm². Hugel and Kohn^556 give more detailed results of their 22 experiments already noted above. In addition to hexadecene, the principal object of study, several other hydrocarbons were investigated. Between 300 and 400° and at pressures above 15 kg/cm², only polymerization takes place. At temperatures above 400° cracking begins; between 400 and 450° decomposition occurs only in the vapor phase, and above 450° also in the liquid phase.

Cohen and Piepenbroek^557 verified the Planck equation for the equilibrium constant up to pressures of 1500 atm, measuring the effect of pressure on the emf of a cell with thallium-amalgam electrodes:

$$ \left(\frac{\partial \log K}{\partial p}\right)_T = -\frac{\Delta V}{kT}. $$

The experimental data are evidently the same as in the article already mentioned^477 on the effect of pressure on the emf, but the calculations are carried out in a different form.

Fawcett and Gibson, R. O.^558 investigated fifty organic reactions up to 160° and 3000 kg/cm². They first discussed theoretically various types of reaction course. They found that reactions which proceed at atmospheric pressure are slowly accelerated under pressure; at 3000 kg/cm² the rate increases on the average by a factor of 5–10.

If a reaction does not proceed at all at atmospheric pressure in the absence of a catalyst, it will not proceed at 3000 atm either. They found that the equilibrium in a tautomeric system can be shifted by pressure.

In a second paper^559 the same authors present the results of studies of the influence of pressure up to 3000 kg/cm² on the rate of formation of cetylpyridinium chloride and bromide.

Here, at first, a very noticeable acceleration with pressure is observed, but there is no influence on the final equilibrium, which is established at atmospheric pressure in 250 hours with a yield of 75%. Several experiments at 6000 kg/cm² gave anomalous results—the yield was lower than at 3000 kg/cm².

Kassel^560 gave a theoretical explanation of monomolecular decomposition at high pressure, in which he arrives at a conclusion contrary to the conclusions of Coffin and Geddes.

Starkweather^561 studied polymerization between 20 and 74° at pressures from 2000 to 9000 kg/cm². A large number of unsaturated organic compounds containing conjugated double bonds polymerize under these conditions; they give a first-order reaction constant with $\Delta E$ equal to approximately 20,000 cal. Increasing the pressure from 6000 to 7000 kg/cm² approximately doubles the rate of polymerization. Bushmakin, Frost, and Ruzhkov^562 investigated the influence of elevated temperatures and pressures up to 350 atm on the oxidation of yellow and red phosphorus, phosphorous acid, and phosphine. Vyazevich and Frolich^563 studied the oxidation of several saturated hydrocarbons from CH₄ to C₇H₁₄ and natural gas by air or oxygen at pressures from 33 to 200 atm. All these are gases, with the exception of C₇H₁₄, which is a liquid.

Coffin and Geddes^564 discussed the possibility of decomposition of complex molecules at high pressures. They found that the rate of homogeneous decomposition of gaseous paraaldehyde slowly decreases with increasing pressure, and proposed a possible mechanism which is applicable to all first-order decomposition reactions of complex molecules.

Poulter and Fraser^565 investigated the action of sulfuric acid on zinc up to 30,000 kg/cm². The rate of dissolution changes little up to 5900 kg/cm². Above this pressure the chemical action practically

ceases, probably as a result of the formation of ice VI. An electrolytic cell with zinc and hydrogen as electrodes changes its polarity at the pressures at which ice VI forms. At $20^\circ$ and $8900$ atm, in the presence of spongy platinum, the reaction proceeds completely:

\[ 4\mathrm{H}_2+\mathrm{H}_2\mathrm{SO}_4 \longrightarrow \mathrm{H}_2\mathrm{S}+4\mathrm{H}_2\mathrm{O}. \]

Basse and Dode $^{566}$ studied the direct oxidation of iodine and iodides under pressure. Iodine combines directly with oxygen to form $\mathrm{J}_2\mathrm{O}_5$, but the yield is very small; thus at $325^\circ$ and $1200\ \mathrm{kg}/\mathrm{cm}^2$ partial pressure of oxygen ($3600\ \mathrm{kg}/\mathrm{cm}^2$ total pressure), in two hours only $2.3\%$ was obtained. Increasing the oxygen pressure or adding platinum black did not increase the yield.

In the oxidation of $\mathrm{KJ}$ under an oxygen partial pressure of $1200\ \mathrm{kg}/\mathrm{cm}^2$ and at a temperature of $410^\circ$, after one hour about $40\%$ $\mathrm{KJO}_3$ is obtained, and after 5–6 hours up to $90\%$. At a higher temperature the reaction proceeds faster, but more free iodine remains.

Dode and Basse $^{567}$ described experiments, most of which are only repetitions of those just cited, but which provide additional material on the formation of $\mathrm{KClO}_3$. $\mathrm{KClO}_3$ cannot be oxidized to $\mathrm{KClO}_4$ at an oxygen pressure of $1200\ \mathrm{kg}/\mathrm{cm}^2$ and temperatures up to $475^\circ$. At higher temperatures rapid decomposition begins.

Basse $^{568}$ studied the synthesis of ammonia at pressures up to $4500\ \mathrm{kg}/\mathrm{cm}^2$ and temperatures up to $1200^\circ\mathrm{C}$. The yield is not sensitive to poisons such as $\mathrm{H}_2\mathrm{S}$ or $\mathrm{CO}_2$. At $850^\circ$ and $4500\ \mathrm{kg}/\mathrm{cm}^2$ the yield does not depend on the presence of a catalyst, and the reaction is practically at equilibrium ($97\%$). At $2000\ \mathrm{kg}/\mathrm{cm}^2$ at this temperature the yield is $40\%$, and at $1000$ atm only $30\%$.

R. O. Gibson, Fawcett, and Perrin $^{569}$ studied the effect of pressure up to $3000\ \mathrm{kg}/\mathrm{cm}^2$ on the reaction between sodium ethylate and ethyl iodide in solution, and at $8500\ \mathrm{kg}/\mathrm{cm}^2$ between pyridine and ethyl iodide. The $K$ in the reaction equation

\[ K=Ae^{-E/RT} \]

increases with pressure to a greater degree for the slow reaction. Both $A$ and $E$ also change with pressure. Vollbrecht and Dittrich $^{570}$ studied the corrosion by hydrogen and by its mixtures with $\mathrm{H}_2\mathrm{S}$ of two steels at $200\text{–}300^\circ$ and pressures up to $200$ atm over $20\,000$ hours. Hydrogen without impurities acts considerably more strongly; in the presence of $\mathrm{H}_2\mathrm{S}$ a protective film of $\mathrm{FeS}$ is formed.

Ipatieff and Freitag $^{571}$ heated $\mathrm{BaSO}_4$ and $\mathrm{Na}_2\mathrm{CO}_3$ to $320^\circ$ in an autoclave; in the presence of a twofold, relative to the equivalent, amount of $\mathrm{Na}_2\mathrm{CO}_3$, $\mathrm{BaSO}_4$ was converted into $\mathrm{BaCO}_3$ by $97\%$.

Kraft, Johnson, and Kirkpatrick $^{572}$ investigated the effect of hydraulic pressure up to $140$ atm on the hardening of cement. In general, the temporary compressive strength of cement decreases with increasing temperature and increases with increasing pressure. Cement hardened

when at $180^\circ\mathrm{F}$ and a pressure of $140\ \mathrm{atm}$, had a temporary resistance $116\ \mathrm{kg}/\mathrm{cm}^2$ greater than that of cement setting at atmospheric pressure at the same temperature. When cement sets at $205^\circ\mathrm{F}$, the corresponding increase in temporary compressive resistance is $240\ \mathrm{kg}/\mathrm{cm}^2$.

Adams $^{573}$ published a theoretical work on the change in activity and the thermodynamic functions associated with it as functions of temperature and pressure, with the aim of obtaining these relations in a convenient form allowing their use in the treatment of experiments carried out under pressure. Adams himself considers the old thermodynamic potential the most convenient.

Lewis $^{574}$ published a theoretical study devoted chiefly to the application of thermodynamic data to gases and gas reactions of interest to industry.

Komar and Ivanov $^{575}$ found that the rate of transformation of white tin into gray decreases at pressures up to $160\ \mathrm{atm}$. The temperature at which the transformation proceeds at the maximum rate shifts from $33^\circ$ at atmospheric pressure to $38^\circ$ at $90\ \mathrm{atm}$. Gillespie $^{576}$ theoretically discussed a method of thermodynamic correlation of gas equilibria at high pressures with the properties of pure gases, and found that the principal shortcoming is the lack of thermodynamic data of sufficient accuracy for pure gases.

Williams, Pirrin, and Gibson R. O. $^{577}$ extended the earlier work of Fawcett and Gibson on reactions in solutions up to $12\,000\ \mathrm{kg}/\mathrm{cm}^2$. Organic reactions fall into three main classes: (1) Normal reactions—pressure accelerates reactions only slightly, and this effect decreases as pressure increases; at $12\,000\ \mathrm{kg}/\mathrm{cm}^2$ the reactions are accelerated only fivefold. (2) “Slow” reactions—pressure accelerates reactions to a much greater extent. At $5000\ \mathrm{kg}/\mathrm{cm}^2$ tenfold, and at $8500\ \mathrm{kg}/\mathrm{cm}^2$ forty-fivefold. (3) Monomolecular decomposition; the results are in agreement with calculations performed by the transition-state method.

Hoffman $^{578}$ found that a pressure of $2000\ \mathrm{kg}/\mathrm{cm}^2$ changes the color of $\mathrm{Pb_2O}$ to grayish-blue, and $3000\ \mathrm{kg}/\mathrm{cm}^2$ to gray. At $12\,000\ \mathrm{kg}/\mathrm{cm}^2$, $\mathrm{Pb_2O}$ acquires a metallic luster, and fused lead scales can be removed from the surface of the oxide. Pressure has no effect on $\mathrm{Pb_3O_4}$.

Steacie, Hatcher, and Rosenberg $^{579}$ developed a more precise method and studied the decomposition of ethyl ether up to $260\ \mathrm{atm}$ and $426^\circ$. Their previous results were confirmed. The reaction rate continued to increase at the highest pressures attained; the reaction cannot be regarded as a simple monomolecular change.

Bon and Newitt $^{580}$ described a high-pressure vessel for studying reactions up to $5000\ \mathrm{atm}$ and used it to study explosive reactions in the $\mathrm{CO_2}—\mathrm{N_2}—\mathrm{O_2}$ system at high pressure and the slow oxidation of hydrocarbons.

Newitt $^{581}$, in a review article, discusses the oxidation of hydrocarbons at high pressures. Pressure has a marked influence on the combustion of aliphatic and aromatic hydrocarbons. It increases the reaction rate, exerts a directing effect on the processes of primary oxidation, and partly determines the distribution of oxygen in the products. Newitt, Linstead, Shapiro, and Burman $^{582}$ described the design and construction of apparatus that they were to use for studies of liquid-phase reactions up to pressures of 5000 and 20,000 atm. Preliminary experiments on the hydrolysis of esters and the Knoevenagel reaction are described. Shapiro, Linstead, and Newitt $^{583}$, in a second paper, studied the polymerization of olefins at pressures up to $10\,000\ \mathrm{kg/cm^2}$. Pressure accelerates polymerization and increases the molecular weight of the polymer, which decreases with temperature.

Terrin and Williams $^{584}$, in the same laboratory of Imperial Chemical Ind., in which the three works mentioned above were carried out, studied the reaction between amines and alkyl halides in acetone solutions. Most of the experiments were carried out at pressures up to $3000\ \mathrm{kg/cm^2}$; however, the reaction of trimethylamine with dimethylaniline in acetone solution was carried out up to $12\,000\ \mathrm{kg/cm^2}$. All these reactions are classified as “slow” under normal conditions, as indicated above in the discussion of work from this same laboratory. They found that the reactions studied are accelerated on average tenfold at $3000\ \mathrm{kg/cm^2}$ and five-hundredfold at $12\,000\ \mathrm{kg/cm^2}$.

Paise $^{585}$ published a theoretical work in which, from spectroscopic data, he calculated dissociation constants for the following reactions at pressures up to 100 atm and temperatures from 1000 to 3000° C:

\[ \mathrm{H_2 \rightleftarrows 2H}; \quad \mathrm{O_2 \rightleftarrows 2O}; \quad \mathrm{H_2O \rightleftarrows H_2 + \tfrac{1}{2}O_2}; \quad \mathrm{H_2O \rightleftarrows H_2 + O}; \quad \mathrm{H_2O \rightleftarrows \tfrac{1}{2}H_2 + OH}; \quad \mathrm{H_2O \rightleftarrows H + OH}; \quad \mathrm{CO_2 \rightleftarrows CO + \tfrac{1}{2}O_2}. \]

Widerølt $^{586}$ studied the corrosion of polished specimens of metals—steel, bronze, Monel metal, nickel, copper, duralumin, aluminum, lead, and zinc—by mixtures of hydrogen and carbon dioxide at pressures up to 31 atm over periods of up to three days.

Pure iron was most strongly subject to corrosion. Steels containing chromium and nickel-chromium were practically not subject to corrosion. In the case of low-carbon steels, the rate of corrosion is proportional to pressure up to 21 atm; above this limit, pressure has a smaller effect.

Weser $^{587}$ published a review article on apparatus and reactions at very high pressures, devoted chiefly to Basset’s work and to ammonia synthesis.

Pient, Shapiro, Linstead, and Newitt $^{588}$ from the I. C. I. laboratory studied the esterification of acetic acid between 50 and 80° and up to 4000 atm. A general discussion is given of the influence of pressure on the activation energy in the Arrhenius equation. It increases with pressure differently for different substances; the greatest observed increase is 40% at 4000 atm.

Shapiro and Pięń[^589] studied the effect of a pressure of 5000 atm on the autoconensation of cyclohexanone and its condensation with aniline. The observed effects were small. Perrin[^590], from the same laboratory, reported to the Faraday Society the results of studies of twelve typical reactions in six different solvents at pressures up to 12,000 kg/cm². An effect of pressure on $A$ and $E$ in the reaction-rate equation $(K = Ae^{-E/RT})$ was found.

The classification of reactions is now presented as follows: (1) “normal” reactions, whose rate increases at 3000 kg/cm² by approximately a factor of two; (2) “normal slow” reactions, whose rate increases tenfold at 3000 kg/cm²; and (3) monomolecular reactions, whose rate decreases with pressure.

Kato[^591] studied the thermal decomposition of rubber wastes in the presence of heavy oil at pressures up to 200 atm. The maximum yield was observed at 180 atm, and the product has the properties of aviation fuel.

Palfray and Sabatier[^592] published a note on catalytic reduction at high pressure. Diniès, Korndorff, Lachinov, and Lelchuk[^593] gave a complete description of the experimental technique used in studying reactions under pressures up to 10,000 kg/cm², and investigated a large number of organic and inorganic reactions, especially condensation, polymerization, and hydrolysis reactions. Extensive tables of results are given.

Michel-Lévy and Viard[^594–^597], in four papers published from 1938 to 1940, investigated the formation of minerals at the high temperatures and pressures produced by an explosion. Powdered mixtures of various substances containing the elements from which minerals could be synthesized were placed in an explosion chamber together with various explosives, the amount of which was chosen so as to obtain, upon explosion, a temperature of the order of 4000° and pressures up to 12,000 kg/cm². After the explosion, the products were kept for several days under a pressure of 3000 kg/cm² and at temperatures up to 700°. Small amounts of many minerals were formed, such as pycnite, willemite, graphite, quartz, cristobalite—all minerals found in granite, anorthite, and sphalerite.

Trifonov and Toshev[^598] subjected three different varieties of brown coals and six varieties of bituminous coals to pressure and found a noticeable difference in the yields of the extraction and distillation fractions, as well as other changes. Morgan[^599] reports that he succeeded in synthesizing acetic acid from methanol and carbon monoxide under pressure, as well as some higher aliphatic acids and alcohols.

Raistrick, Shapiro, and Newitt of I.C.I. studied the polymerization of cyclopentadiene and $\alpha$-dicyclopentadiene between 0 and 40° and up to 5000 atm. Three stages of the process are distinguished: (1) dimerization, (2) formation of higher polymers, (3) explosive decomposition, occurring for each temperature within definite pressure limits and

accompanied by the formation of a carbonaceous residue and a large quantity of gas. The constant of the bimolecular reaction was determined. Details of the explosive processes were studied in the next paper of this series.

Stupochenko $^{601}$ published a paper on a possible mechanism of the influence of pressure on chain gas reactions; at high pressures one should expect a “crowding effect,” a decrease in the reaction rate, and low diffusion rates.

Muraur and Basse $^{602}$ subjected various solid explosives to a gas pressure of $12\,000$ atm, produced by argon, nitrogen, and hydrogen, and found that the character of decomposition changes greatly and tends to proceed without accompanying mechanical effects. Under these conditions nitroglycerin and picric acid burn without detonating.

Goltermann $^{603}$ studied the oxidation by gaseous oxygen at 300 atm of strontium, barium, lead, manganese, and cobalt. Hieber and Lagally $^{604}$ investigated the carbonyls of various metals at 760 atm. Lachinov $^{605}$ discusses in detail the industrial application of high pressures in the field of fuel gasification and the production of alcohols, aldehydes, ketones, acids, metal carbonyls, urea, etc.

Yuell $^{606}$ published a theoretical paper on the calculation of chemical equilibria in gases at high pressures. Andreev $^{607}$ studied the combustion of explosives under pressure up to $700\ \mathrm{kg}/\mathrm{cm}^{2}$. The pressure could not exceed this maximum because of rupture of the lead disks or tubes.

Leipunsky and Reinov $^{608}$ described a micromethod for studying reactions up to $450^\circ$ and $12\,000$ atm. Shatenshtein $^{609}$ described apparatus made of glass and chromium-nickel steel, used at the Karpov Institute for the study of the chemical properties of solutions and reactions in liquefied gases under pressure.

Matsui and Yasuda $^{610}$ investigated the oxidation of methane at a pressure of 100 atm.

Adams $^{611}$ of the geophysical laboratory published a review article in which he summarized theoretical and experimental work at pressures up to several thousand atmospheres and $1000^\circ$. The possible application of the results to the production of refractories, petrology, and volcanology is discussed.

Gibson and Loeffler $^{612}$ of the same laboratory studied the effect of pressure up to $12\,000\ \mathrm{kg}/\mathrm{cm}^{2}$ on the acidity of aqueous solutions. The dissociation constant of weak bases and weak acids increases with increasing pressure. Cresol red and bromophenol blue were used as indicators. The influence of pressure on the dissociation constant of the indicators was not determined. The results do not differ from those obtained by Brander by the electrical-conductivity method.

Owen and Brinkley $^{613}$ published a theoretical article on the influence of pressure on ionic equilibrium in pure water and in salt solutions on

on the basis of experiments carried out in a geophysical laboratory up to 1000 bar. The influence of pressure on the ionization of pure water was calculated.

Gillespie^614 wrote a review theoretical paper on thermodynamic methods for calculating the influence of pressure on gaseous reactions from the equation of state: the main thing needed is still better experimental data. The author refers to an as-yet unpublished equation of state of Keyes, which should give better agreement.

Trifonov and Filippov^615 compressed six varieties of Bulgarian brown coals up to $10\,000\ \mathrm{kg}/\mathrm{cm}^2$ and obtained definite changes in properties. The influence of pressure depends on the duration of its application. In general, pressure affects both the yield of products during distillation and an increase in the distillation temperature.

Krichevskii and Bolshakov^616 studied heterogeneous equilibria in the nitrogen–ammonia system between 90 and $125^\circ$ and up to $5000\ \mathrm{atm}$. The critical curve has a temperature minimum between 85 and $90^\circ$, and barotropic phenomena are observed.

Kazarnovskii and Karapet’yants^617 calculated the heat of formation of ammonia between 250 and $500^\circ$ up to $1000\ \mathrm{atm}$ by an improved method which, as the authors state, enabled them to establish errors in previously published data. At the highest temperatures and pressures the heat of formation is approximately 20% greater than at atmospheric pressure.

Fuchs^618 theoretically calculated the influence of pressure on the equilibrium constant of ammonia from an equation of state with a second virial term. It is indicated that the dipolar character of $\mathrm{NH}_3$ does not seriously affect the calculations. Good agreement with experiment was obtained up to $300\ \mathrm{atm}$, from which point deviations begin that are ascribed to an increase in the virial coefficient.

Volarovich and Leont’eva^619 studied the influence of pressure up to $500\ \mathrm{kg}/\mathrm{cm}^2$ on the linear rate of crystallization of a melt containing 73.3% $\mathrm{SiO}_2$ and 26.7% $\mathrm{Na}_2\mathrm{O}$. The crystallization rate increases eightfold at this pressure, while the temperature corresponding to the maximum linear crystallization rate changes from 260 to $740^\circ$.

Dickey^620 wrote an article in which he summarized the use of high-pressure apparatus in the organic-synthesis industry and listed forty-nine different reactions that can be substantially improved by pressure within the range from 5 to $400\ \mathrm{atm}$.

CITED LITERATURE

G. Komatsu and M. Masumoto, Bull. Chem. Soc. Japan 5, 241 (1930).
Catalytic action at high pressures and temperatures. Catalytic hydrogenation of ethers.
S. Komatsu and M. Hagiwara, J. Chem. Soc. Japan 51, 552 (1930).
Catalytic action at high pressures and temperatures. II. Catalytic action of reduced copper on phenols.

G. Hughes et Cohn, Chim. Ind. Spec. No. 201 (March 1930). Reactions occurring in pure unsaturated hydrocarbons under the influence of heat and high pressure.
L. J. Gillespie and J. A. Beattie, Phys. Rev. 36, 743 (1930). Thermodynamic treatment of chemical equilibria in systems of real gases. I. An approximate equation for the equilibrium constant, applied to existing data for the water-gas equilibrium.
V. Njewoglan, Arch. Chem. Farm. 4, 49 (1930). Thermodynamics of high pressure.
V. N. Ipatiev and B. Muromtsev, Vest. 63 B, 160 (1930). Displacement of metals and their oxides from solutions of their salts by hydrogen at high temperatures and pressures. Action of hydrogen on metal nitrates.
V. N. Ipatiev, G. A. Razuvayev and V. Malyunovskii, Ber. 63 B, 166 (1930). Displacement of metals and their oxides from solutions of their salts by hydrogen at high temperatures and pressures. Displacement of arsenic from its salts by hydrogen.
G. T. Morgan et al., Proc. Roy. Soc. 127, 240 (1930). Discussion of catalytic reactions at high pressures.
W. A. Bone, Trans. Inst. Chem. Ings. 8, 98 (1930). Reactions at high pressures.
S. Komatsu and K. Mitsui, Mem. Coll. Sci. Kyoto. Imp. Univ. A14, 297 (1931). Catalytic action of high temperatures and high pressures. I. Catalytic hydrogenization of benzoic acid.
S. Tonaka and R. Amatatsu, J. Chem. Soc. Japan 52, 611 (1931). Catalytic action at high pressures and high temperatures. VII. Catalytic hydrogenization of safrole.
L. Lewon and H. Eyring, J. Am. Chem. Soc. 52, 2801 (1931). Stability of nitrogen pentoxide at 1000 atm in an oxygen atmosphere in the presence of nitrogen tetroxide.
H. Adkins, H. I. Cramer and E. Connor, J. Am. Chem. Soc. 53, 1402 (1931). Rate of hydrogenization of acetoacetic ester, tiglic acid, benzene, phenol and aniline over nickel at pressures from 27 to 350 atm.
G. T. Morgan, Chem. Ind. 50, 104 (1931). Organic syntheses accelerated by pressure.
G. Tamman and A. Pape, Zschr. f. anorg. allg. Chemie 200, 113 (1931). Influence of pressure on the rate of polymerization.
V. V. Ipatiev (Jr.) and V. I. Tikhomirov, Ber. 64 B, 1951 (1931). Displacement of sulfur from solutions of its salts by hydrogen under pressure.
V. V. Ipatiev, M. N. Platonova and B. S. Malyunovskii, Ber. 64 B, 1959 (1931). Displacement of arsenic from solutions of its salts by hydrogen under pressure.
V. V. Ipatiev, I. R. Molkenin and V. P. Teodorovich, Ber. 64 B, 1964 (1931). Displacement of bismuth from solutions of its salts by hydrogen under pressure.
V. V. Ipatiev (Jr.) and V. P. Teodorovich, Zhurn. obshch. khim. 1, 779 (1931). Theory of the replacement of metals by hydrogen under pressure. II. Separation of the metals of the fifth group in solutions of their chlorides under pressure.
G. Tamman and A. Riepnbeck, Zschr. f. anorg. allg. Chemie 207, 368 (1932). Behavior of certain carbon compounds upon heating them to 650° under an initial pressure of 1000 atm.
G. G. Brown and M. Souders Jr., Oil a. Gas J. 31, 41 (1932). Properties of paraffin hydrocarbons and design of high-pressure apparatus.
G. G. Brown and M. Souders, Jr. and R. I. Smith, Ind. Eng. Chem. 24, 513 (1932). Principles of designing high-pressure apparatus and high-...

vaporization for paraffin hydrocarbons. I. Dependence of $P$-$V$-$T$ for paraffin hydrocarbons.

P. Leone u. S. Vinti, Ann. Chim. Appl. 22, 395 (1932). Effect of pressure on cellulose saccharification.
T. E. Warren, Can. Dept. Mines, Mines Branch Report 725-1, 15 (1932). Effect of pressure on the pyrolysis of methane.
G. Hugel et Kohn, Ann. Comb. Liquides 7, 15 (1932). Effect of high temperatures and pressures on pure unsaturated hydrocarbons.
G. Hugel et Jean Friess, Ann. Comb. Liquides 6, 1109 (1931); 7, 59 (1932). Hydrogenation of several derivatives of coal tar (1) in the presence of sodium hydride as catalyst (2) at high pressures and high temperature.
J. B. Conant a. W. R. Peterson, J. Am. Chem. Soc. 54, 628 (1932). Polymerization reactions at high pressures. II. Reaction mechanism.
G. Hugel et Kohn, Ann. Comb. Liquides 7, 239 (1932). Effect of high temperatures and pressures on pure unsaturated hydrocarbons.
E. Cohen u. K. Piepenbrock, Zschr. f. Physik. Chemie A167, 365 (1933). Effect of pressure on chemical equilibria in condensed systems.
E. W. Fawcett a. R. O. Gibson, J. Chem. Soc. 386 (1934). Effect of pressure on a number of organic reactions in the liquid phase.
E. W. Fawcett a. R. O. Gibson, J. Chem. Soc. 396 (1934). Effect of pressure on the rate of formation of cetylpyridinium halides.
L. S. Kassel, J. Chem. Phys. 2, 106 (1934). Monomolecular decomposition at high pressure.
H. W. Starkweather, J. Am. Chem. Soc. 56, 1870 (1934). Polymerization at high pressure.
I. N. Bushmakin, A. V. Frost and M. V. Ruzhkov, Four articles in Zhurn. prikl. khim. 6, 588—620 (1934). Oxidation at elevated temperatures and pressures of yellow and red phosphorus.
P. J. Wiezewich a. P. K. Frolich, Ind. Eng. Chem. 26, 267 (1934). Direct oxidation of saturated hydrocarbons under pressure.
C. C. Coffin a. A. L. Geddes, J. Chem. Phys. 2, 47 (1934). Decomposition of complex molecules at high pressures.
T. C. Poulter a. G. E. Fraser, J. Phys. Chem. 38, 1131 (1934). Action of acids on zinc at pressures from one to thirty thousand atmospheres.
James Basset et Maurice Dodé, Comptes rendus 199, 668 (1934). Direct oxidation of iodine and iodides at high pressure.
M. Dodé et J. Basset, Bull. Soc. Chim. 2, 344 (1935). Direct oxidation of iodine, iodides, and chlorates at very high pressures.
J. Basset, Bull. Soc. Chim. 2, 108 (1935). Synthesis of ammonia at pressures above 1000 atm and chemistry of very high pressures.
R. Gibson, E. W. Fawcett a. M. W. Perrin, Proc. Roy. Soc. London 150, 223 (1935). Effect of pressure on reactions in solutions. I. Sodium ethylate and ethyl iodide up to 3000 $kg/cm^2$. II. Pyridine and ethyl iodide up to 8500 $kg/cm^2$.
H. Vollbrecht u. E. Dittrich, Chem. Fabrik 193 (1935). Action of hydrogen and hydrogen sulfide on steel at high pressures and temperatures.
V. N. Ipatieff a. C. Freitag, Ind. Eng. Chem. 27, 342 (1935). Volume decomposition and oxidation of inorganic compounds under pressure. Conversion of heavy spar into barium carbonate.
B. C. Craft, T. J. Johnson a. H. L. Kirkpatrik, Trans. Am. Inst. Min. Met. Eng. 114, 62 (1935). Effect of temperature, pressure, and the ratio of water to cement on the setting time and strength of cement.

L. H. Adams, Chem. Rev. 19, 1 (1936). Activity and the thermodynamic quantities connected with it; their determination and variation with temperature and pressure.
W. K. Lewis, Ind. Eng. Chem. 28, 257 (1936). Application of physical data to processes at high pressure.
A. Komar and K. Ivanov, Zh. E. T. F. 6, 256 (1936). Effect of pressure on the linear rate of transformation of white tin into gray tin.
L. J. Gillespie, Chem. Rev. 18, 359 (1936). Methods of thermodynamic correlation of gas equilibria at high pressures with the properties of pure gases.
E. G. Williams, M. W. Perrin and R. O. Gibson, Proc. Roy. Soc. 154, 684 (1936). Effect of pressure up to 12,000 kg/cm² on reactions in solutions.
J. Hoffmann, Zschr. f. anorg. allg. Chemie 228, 160 (1936). Changes caused in oxides by light and pressure.
E. W. R. Steacie, W. H. Hatcher and S. Rosenberg, J. Chem. Phys. 4, 220 (1936). Kinetics of decomposition of ethyl ether at high pressures.
W. A. Bone and D. M. Newitt, Chem. Eng. Cong. World Power Conf., Adv. Proof No. GS (1936). Reactions in the gas and liquid phases at high pressures.
D. M. Newitt, Chem. Rev. 21, 299 (1937). Oxidation of hydrocarbons at high pressure.
D. M. Newitt, R. P. Linstead, R. H. Shapiro and E. J. Boorman, J. Chem. Soc. 876 (1937). Liquid-phase reactions at high pressures. I. Hydrolysis of ethers and reaction of Knoevenagel.
R. H. Shapiro, R. P. Linstead and D. M. Newitt, J. Chem. Soc. 1784 (1937). Liquid-phase reactions at high pressures. II. Polymerization of olefins.
M. W. Perrin and E. G. Williams, Proc. Roy. Soc. 159, 162 (1937). Effect of pressure up to 12,000 kg/cm² on reactions between amines and alkyl halides in acetone solution.
H. Zeise, Zschr. f. Elektrochemie 43, 704 (1937). Dependence of certain technically important gas equilibria on temperature and pressure.
W. Wiederholt, Zschr. b. Ver. d. Ing. 81, 324 (1937). Corrosion of metal by water and carbonic acid at elevated pressure.
Bruno Waeser, Chem. Zeitung 534 (1937). Reactions at high pressure and the necessary apparatus.
P’eng Shu-Lin, R. H. Shapiro, R. P. Linstead and D. M. Newitt, J. Chem. Soc. 784 (1938). Liquid-phase reactions at high pressures. III. Esterification of acetic acid.
R. H. Shapiro and P’eng Shu-Lin, J. Chem. Soc. 117 (1938). Liquid-phase reactions at high pressures. IV. Autocondensation of cyclohexanone and its condensation with aniline.
M. W. Perrin, Trans. Faraday Soc. 34, 144 (1938). Effect of hydrostatic pressure on reaction rate.
Tsunetaro Kato, J. Soc. Chem. Ind. Japan 41, Suppl. 83 (1938). Thermal decomposition of rubber at high pressure. IV and V. The quality of gasoline obtained by cracking waste rubber in the presence of heavy oil in comparison with aviation gasoline.
L. Palfray and S. Sabetay, Bull. Soc. Chim. 5, 1423 (1938). Laboratory note. Catalytic reduction at high pressure.
A. I. Dintses, B. A. Korndorf, S. S. Lachinov and S. L. Lel’chuk, Uspekhi Khimii 7, 1173 (1938). Chemical reactions at ultrahigh pressures.
A. Michel-Lévy and Jean Wyart, Comptes rendus 206, 261 (1938). Production of minerals at high temperatures and pressures, obtained upon detonation of explosive substances.

A. Michel-Lévy and J. Wyart, Comptes rendus 208, 1594 (1939). Synthesis of quartz by pneumatolysis with the aid of brisant explosives. Formation of liquid inclusions.
A. Michel-Lévy and J. Wyart, Comptes rendus 208, 1030 (1939). Synthesis of anorthite by pneumatolysis with the aid of brisant explosive substances.
A. Michel-Lévy and J. Wyart, Comptes rendus 210, 733 (1940). Formation of cristobalite and quartz upon further heating of vitreous silicon dioxide under high pressure produced by explosives.
I. Trifonov and G. Toshev, Brennstoff—Chem. 20, 128 (1939). Change in the properties of coals upon compression under high pressure.
G. T. Morgan, Dept. Sci. Ind. Research (Brit.) Chem. Research Board. Triennial Report, 27—40 (1935—1937). Report of the Director on chemical research. III. Studies at high pressures.
B. Raistrick, R. H. Shapiro and D. M. Newitt, J. Chem. Soc., 1761 (1939). Liquid-phase reactions at high pressures. V. Polymerization of cyclopentadiene and α-dicyclopentadiene.
E. V. Stupochchenko, Acta URSS 11, 555 (1939). Possible mechanism of the effect of pressure on the kinetics of strong gas reactions.
H. Muraour and J. Basset, Comptes rendus 208 (1939). Effect of high pressures on the propagation of reactions in solid explosive substances.
C. B. Holtermann, Ann. Chim. 14, 121 (1940). Direct oxidation at high pressures. Oxides of strontium, barium, lead, manganese, and cobalt.
W. Hieber and H. Lagally, Zschr. f. anorg. allg. Chemie 33, 245, 295 (1940), 34, 245, 350 (1940); 35, 245, 321 (1940). Metal carbonyls.
C. S. Lachinov, Izv. Ak. Nauk SSSR 963 (1940). Recent achievements and prospects for the application of high pressures in the basic chemical industry.
R. H. Ewell, Ind. Eng. Chem. 32, 147 (1940). Calculation of chemical equilibrium at high pressure.
K. K. Andreev, Dokl. Ak. Nauk SSSR 29, 469 (1940). Combustion of explosive substances under increasing pressure.
O. I. Leipunskii and N. M. Reinov, Zhurn. tekhn. fiz. 10, 596 (1940). Micromethod for the study of chemical reactions at high pressures.
A. I. Shatenshtein, Acta URSS 13, 604 (1940). Apparatus for studying the physicochemical properties of solutions and for studying reactions in compressed gases under pressure.
A. Matsui and M. Yasuda, J. Soc. Chem. Ind. Japan 43, Suppl. 453 (1940). Oxidation of methane under pressure.
L. H. Adams, Chem. Rev. 29, 447 (1941). Equilibria in a heterogeneous system at high temperatures and pressures.
R. F. Gibson and O. H. Loeffler, Trans. Am. Geoph. Union 503 (1941). Effect of pressure on the acidity of aqueous solutions.
B. B. Owen and S. R. Brinkley, Jr., Chem. Rev. 29, 3 (1941). Calculation of the effect of pressure on ionic equilibria in pure water and in salt solutions.
L. J. Gillespie, Chem. Rev. 29, 525 (1941). Thermodynamic calculation of the effect of pressure on gas reactions from the equation of state. A brief review.
I. Trifonov and A. Filippov, Brennstoff Chem. 22, 22, 193 (1941). Changes occurring in coal compressed to high pressure.
I. R. Krichevskii and P. Bolshakov, Acta URSS 14, 53 (1941). Heterogeneous equilibria in the ammonia—nitrogen system at high pressures.
Ya. S. Kazarnovskii and M. K. Karpetyants, Zhurn. fiz. khim. 15, 966 (1941). Effect of pressure on the heat of formation of ammonia.

K. Fuchs, Proc. Roy. Soc. 179, 433 (1942). Dependence of the phase-equilibrium constant on pressure.
M. P. Voronich and A. A. Leont’eva, Zhurn. fiz. khim. 17, 45 (1943). The effect of pressure on the linear growth rate of crystals of silicates.
I. V. Dickey, Synthetic Organic Chemicals 16, 1 (1944). Eastman Kodak Co., Kahester, New York. Application of equipment operating under pressure for organic syntheses.

THE EFFECT OF PRESSURE ON BIOLOGICAL EFFECTS

This is the field of research under pressure in which a relatively greatest increase in activity is observed. At the time my book was written only a few studies had been carried out, whereas now about forty-five new investigations have been completed.

The largest number of studies has been performed in four principal centers: in Paris by Basset and co-workers, at Pennsylvania State University by Dow and co-workers, at Princeton by Brown and Marsland and co-workers, and by Ebbecke, Haubring, and their co-workers in Germany.

Basset and Macheboeuf$^{621}$ found that a pressure of $6000\ \mathrm{kg/cm^2}$ kills Bacillus prodigiosus, Staphylococcus aureus, and Koch’s bacilli.

Spores of Bacillus subtilis do not perish at $17\,500\ \mathrm{kg/cm^2}$ over forty-five minutes. Various diastases are sensitive to pressure; their activity decreases by approximately one-third at $9000\ \mathrm{kg/cm^2}$ and disappears completely at $15\,000\ \mathrm{kg/cm^2}$.

Tetanus toxin is destroyed by pressure at $13\,500\ \mathrm{kg/cm^2}$; the activity of diphtheria toxin decreases to $1\%$ after 45 minutes’ exposure at a pressure of $17\,500\ \mathrm{kg/cm^2}$.

Cobra venom and tuberculin are not decomposed by a pressure of $17\,500\ \mathrm{kg/cm^2}$ over forty-five minutes.

Basset and Macheboeuf$^{622}$, in a subsequent article, reported that tetanus toxin inactivated by pressure does not produce antitoxin. Antitoxin from horse serum immunized against tetanus retains appreciable antitoxic activity after a 45-minute exposure under a pressure of $13\,500\ \mathrm{atm}$.

Basset, Wollman, Macheboeuf, and Bardach$^{623}$ found that various bacteriophages are considerably more sensitive to pressure than the corresponding bacteria. A pressure of $3000\ \mathrm{kg/cm^2}$ usually destroys the activity of a bacteriophage. In the presence of the corresponding bacterium, the resistance of the bacteriophage increases.

Basset, Lisbonne, and Macheboeuf$^{624}$ found that pressure completely destroys the activity of dog gastric juice with respect to acidification, but does not destroy prokinase and does not affect activation by calcium. At $15\,000\ \mathrm{kg/cm^2}$, exposures reached up to forty-five minutes. Pancreatic lipase is completely destroyed under these conditions; activ-

the activity of amylase decreases to $2/3$, and that of trypsin to one half. Basset and Macheboeuf $^{625}$ summarized the results of the above-mentioned works in German.

Basset, Macheboeuf, and Sandor $^{626}$ found that blood serum coagulates completely under a pressure of $6000\ \mathrm{kg}/\mathrm{cm}^{2}$ over thirty minutes at $18^\circ\mathrm{C}$. Pure globulin, endoglobulin, and pseudoglobulin coagulate at $15\,000\ \mathrm{kg}/\mathrm{cm}^{2}$. Coagulation apparently is not accompanied by noticeable chemical changes. Macheboeuf, Basset, and Lévy $^{627}$ investigated the influence of pressure on diastases and toxins, studying, in addition to the factors considered earlier, the effect of changing the exposure time and changing the $pH$ of the solution. Basset, Macheboeuf, and Perez $^{628}$ found that the anaphylactic specificity of serum is completely destroyed by pressures greater than $4000\ \mathrm{kg}/\mathrm{cm}^{2}$, and that serum treated in this manner acquires a new antigenic specificity.

Basset, Eugène Wollman, Elisabeth Wollman, and Macheboeuf $^{629}$ found that spores of Bacterium subtilis infected with the corresponding bacteriophage withstand pressures up to $13\,500\ \mathrm{kg}/\mathrm{cm}^{2}$, whereas a bacteriophage mixed with a simple culture, and not with spores, is completely inactivated at $7500\ \mathrm{kg}/\mathrm{cm}^{2}$. The bacteriophage of Bacterium megatherium is inactivated at $6500\ \mathrm{kg}/\mathrm{cm}^{2}$; a lysogen from a culture of spores of the same bacteria withstands $9500\ \mathrm{kg}/\mathrm{cm}^{2}$.

Basset, Wollman, Macheboeuf, and Bardach $^{630}$ found that the active principle of many tumors is extremely sensitive and is inactivated at $1800\ \mathrm{kg}/\mathrm{cm}^{2}$. The active principle of the Py sarcoma has a resistance of the same order as that of bacteriophages.

Basset, Nicolau, and Macheboeuf $^{631}$ experimented with five different viruses; all of them withstand $2000\ \mathrm{kg}/\mathrm{cm}^{2}$ and are inactivated at pressures from $3000$ to $7000\ \mathrm{kg}/\mathrm{cm}^{2}$. Lepine, Basset, and Macheboeuf found that the avian plague virus is destroyed after a 30-minute exposure at $4000\ \mathrm{kg}/\mathrm{cm}^{2}$. Thus, the inactivated virus has a weak immunizing capacity.

On the basis of the different relation to pressure, one may draw the conclusion that viruses and diastases differ in nature. Macheboeuf and Basset $^{633}$ wrote an article summarizing their biological works.

Wollman, Macheboeuf, Bardach, and Basset $^{634}$ found that the active principle of Shope papilloma withstands pressure up to $4000\ \mathrm{atm}$ and is destroyed at $6000\ \mathrm{kg}/\mathrm{cm}^{2}$. The active principle of the Brown–Pearce cancerous tumor behaves similarly to certain mouse tumors studied earlier; it withstands $1000\ \mathrm{kg}/\mathrm{cm}^{2}$ and is destroyed at $1300\ \mathrm{kg}/\mathrm{cm}^{2}$; this is the most sensitive of all the substances found.

Basset, Macheboeuf, and Wollman $^{635}$ presented a detailed summary of all their work for the Pasteur Institute. It included: a description of the apparatus and experimental technique, the action of pressure on spore-forming and non-spore-forming bacteria, on diastases and toxins, studies on immunity, on ultraviruses and filterable viruses, immu-

...neutralizing capacity of viruses inactivated by pressure, and work with bacteriophages and neoplasms.

Basset, Gratia Macheboeuf, and Manil[^636] described in an American journal experiments showing that there is a noticeable effect of a pressure of the order of $2000 \text{ kg}/\text{cm}^2$ on the tobacco virus; at $6000 \text{ kg}/\text{cm}^2$ it retains only $58\%$ of its virulence, and at 8000 only $2\%$.

It seems to me necessary to make one general caution with regard to all the work of Basset and his collaborators, which will complicate the interpretation of results obtained at pressures above $8000 \text{ kg}/\text{cm}^2$. The fact that water freezes and gives ice VI at these pressures, evidently, was never taken into account and was not commented upon. Recently performed, but unpublished, experiments by Boyd and me, in which we approached the conditions of Basset’s experiments, showed that not only does water freeze out from its biological solutions at these pressures, i.e. that the presence of biological substances does not affect the preservation of the liquid phase during supercooling, but also that the transition from liquid to ice is accompanied by a break in the biological effects.

At the Pennsylvania State University, River, Popp, and Dou[^637] found that pressures of the order of several thousand atmospheres accelerate and improve the germination of seeds having a water-impermeable coat, but do not affect those seeds which have embryonic rudiments. Pressure acts mechanically, driving water or oxygen into the seed and accelerating physiological processes.

Dou[^638] described the effect of pressure between 3000 and 7000 atm on various proteins. Hemoglobin, pepsin, renin, and insulin in aqueous solutions are denatured. Other phenomena occur in urine, blood, and milk. Milk is sterilized because of the destruction of lactobacilli. Pressure fragments the erythrocytes of blood and coagulates it. Dou and Mathews[^639] compressed blood to $13\,000 \text{ kg}/\text{cm}^2$ and obtained complete coagulation of the blood and destruction of all erythrocytes and leukocytes at a pressure of $3500 \text{ kg}/\text{cm}^2$ for six hours, or $13\,000 \text{ kg}/\text{cm}^2$ for 3.5 hours. The proteins of the red corpuscles coagulate more readily than the plasma protein.

The authors do not believe that the effect of pressure is reducible to a mechanical effect, i.e. to the destruction of cell membranes, but consider it chemical.

Dou[^640], in a popular article, described certain details of cooperation between the physical and biological departments in these biological studies.

Dou, Mathews, and Torp[^641] found that the physiological activity of insulin does not decrease during prolonged holding at $10\,000 \text{ kg}/\text{cm}^2$, although it does coagulate. Mathews, Dou, and Anderson[^642] found that the activity of renin and pepsin decreases as the pressure is increased and disappears completely at pressures from 5000 to $6000 \text{ kg}/\text{cm}^2$. The effect depends strongly on temperature. Up to 10,000 atm there occurs no...

no changes in the amino-nitrogen content, which indicates the absence of hydrolysis under pressure. Both substances coagulate strongly under pressure; in this process the same substance is obtained as in thermal coagulation. Since the changes in energy upon heating and upon compression are entirely different, these changes alone cannot explain the phenomena that occur.

Grant, Dow, and Franks643 dissolved 20 grams of powdered egg albumin (Merck) in 500 cm³ of water and compressed it from 1000 to 7500 kg/cm². Coagulation occurred at all pressures, and the higher the pressure, the greater it was. Loeffler and Dow644 found that tobacco virus is almost completely inactivated at 7500 kg/cm². A coagulum is also formed, most of all between 6000 and 8000 atm. Coagulation at 7500 kg/cm² apparently proceeds according to a first-order reaction. Inactivation at high pressures proceeds considerably faster than coagulation, and their mechanisms are probably different.

Biological investigations associated with the names of Brown and Marsland began with a separate work by Brown in 1934645, concerning the influence of rapid changes in hydrostatic pressure on the contraction of skeletal musculature.

Marsland’s first paper646, in 1935, was devoted to the influence of pressure on cell division in the egg of Arbacia. Pressure between 1 and 333 atm reduced the rate at which cleavage furrows appeared along the axis of the cell. At pressures up to 450 atm the furrows that had already formed disappear. The effect is reversible if the pressure is not maintained for more than fifteen minutes. Here, apparently, there is a close connection with the influence of pressure on viscosity.

Marsland647 found that, under a pressure of 600 atm, the gel which forms in the cell under normal conditions undergoes a liquefaction that increases with pressure.

Marsland648 found that, under pressure up to 600 atm, the rate of protoplasmic streaming in Elodea canadensis regularly decreased as the pressure increased. Brown, Johnson, and Marsland649 studied the effect of pressure up to 500 kg/cm² on the luminescence of three strains of bacteria. These bacteria had a temperature optimum of luminescence from 21 to 32°. Below the optimum temperature, pressure decreases luminescence; above the optimum, it increases it. The pressure was maintained for less than three minutes, and the effect was strictly reversible.

Luminescence is possibly caused by two different causes acting in opposite directions: the optimum temperature is that at which the rates are equal. The influence of pressure is explained by the slowing of both reactions, which, it is assumed, normally proceed with an increase in volume.

Johnson, Brown, and Marsland650, in the following work, supplemented their conception of the mechanism explaining the influence of pressure on luminescence by including an enzymatic equilibrium shifted by pressure.

Johnson, Eyring, and Williams $^{651}$ examined the nature of enzyme inhibition in bacterial luminescence produced by sulfanilamide and urethane, and at the same time discussed the influence of pressure.

Johnson, Brown, and Marsland $^{652}$ found that the luminescence of Photobacterium phosphoreum, which under normal conditions is suppressed by the action of certain narcotics, is restored by a pressure of $500\ \mathit{atm}$. In these cases pressure alone, without narcotics, has little effect on luminescence. On the other hand, there are certain narcotics whose inhibitory effect does not change with pressure. The explanation lies in the existence of an equilibrium sensitive to pressure changes among certain enzymes.

Marsland and Brown $^{653}$ described an apparatus operating under pressure with windows through which one can record the time of fall of a small ball in various protoplasmic gels. Myosin and methylcellulose show an increased degree of liquefaction with increasing pressure; gelatin becomes considerably denser.

Ebbeck $^{654}$ found that paramoecia can be subjected to a pressure of $800\ \mathit{atm}$ without suffering irreversible damage. Ebbeck and Hasenbring $^{655}$ compressed various marine organisms and observed various excitatory and paralytic phenomena.

Haubrich $^{656}$ studied the influence of exposure time, temperature, and season of the year on the irreversible damage caused by pressure in frog erythrocytes. Deuticke and Ebbeck $^{657}$ found that the contraction of muscles produced by hydrostatic pressure of $500\ \mathit{atm}$ is accompanied by the same chemical changes as in the normal functioning of the muscle.

Ebbeck and Haubrich $^{658}$ found that if the coagulability of blood is lowered by the addition of certain substances, coagulation can be completely suppressed by pressures from 200 to $800\ \mathit{atm}$.

Haubrich $^{659}$ found that, up to pressures of $800\ \mathit{atm}$, the retarding effects of pressure on contraction and on coagulation proceed parallel to one another.

Ebbeck $^{660}$, in an article devoted mainly to other questions, discusses the mechanism of the influence of pressure on coagulation; it is assumed that pressure acts as a stabilizing influence on the coagulating system. Ebbeck and Zipf $^{661}$ found that the coagulation of blood compressed to 1000 or $2000\ \mathit{atm}$ is slowed or ceases. When the pressure is released, the blood clot that forms has a softer consistency than usual and does not contract. Fibrinogen solutions show the same effect.

Let us now touch on incidental papers concerning biological effects. Wilson and Poulter in 1929 $^{662}$ published, in a journal not readily accessible, the results of experiments that were not included in my book. They found that pressures up to $12000\ \mathit{atm}$ are necessary to kill certain bacteria. The more complex the bacterium, the lower the required pressure. Hydra and planaria continue to exist even at $1300\ \mathit{atm}$.

It is assumed that pressure precipitates certain colloidal substances.

The effect of pressure on the precipitation of other colloids—such as sulfur, silver, gold, ferric hydroxide, molybdenum blue, and Prussian blue—was studied. Colloidal ferric hydroxide precipitates completely at 100 atm, whereas even 17,000 kg/cm² has very little effect on molybdenum blue.

Lloyd and Moran$^{663}$ studied isoelectric gels up to 3200 atm. Pure water is displaced from the gel by pressure; the concentration of the remaining gel is a function of pressure. Katz’s thermodynamic equation for swelling was applied to these data.

Moran$^{664}$ investigated the effect of pressures up to 2500 atm on the composition of various gelatin–NaCl gels containing up to 15% gelatin and from 1 to 15% NaCl. The amount of NaCl remaining in the gel after the application of pressure is a linear function of the initial concentration. Increasing the pressure reduces the amount of water remaining in the gel.

Cattell$^{665}$ published a review article on the known biological effects of pressure. Grundfest$^{666}$ found that the sensitivity of a frog nerve increases up to 400 atm and then decreases up to 700 atm.

Bantaus$^{667}$ discovered that the growth of tissue cultures is suppressed at pressures above 1000 atm; the growth of fibroblasts in cultures of chick-embryo heart is completely suspended above 1850 atm. Deuticke and Garren$^{668}$ studied enzyme reactions in muscles up to 800 atm. Metabolic processes in muscles are accelerated, but inhibition occurs with respect to certain enzymes. The effect depends on the duration of pressure application.

Glycolysis in blood is delayed at 2000 atm, but a pressure of 800 atm has no effect on it.

Deuticke and Hasenbring$^{669}$ studied chemical processes during isotonic and isometric contraction of muscles produced under pressures up to 500 atm. Some phenomena occurring under pressure change sign with the passage of time.

Leipunskii$^{670}$ studied the coagulation of gelatin. The transition of a sol into a gel is accelerated by pressure. Viscosity measurements showed that at 2000 atm coagulation is accelerated by a factor of 2 to 2.5.

Kitching and Moser$^{671}$ found that a pressure of 340 atm stops all movements in an amoeba; after the pressure is removed, movement is completely restored. No permanent disturbances are observed for exposures of several minutes even at 680 atm.

Nakajima and Ikeda$^{672}$ studied the hydrolysis of caseinogen protein and cow gelatin at temperatures between 140 and 195° and pressures from 38 to 185 atm for 4–5 hours. The complex products were analyzed. No formation of any unusual compounds was detected.

Pize and Regnery^673 subjected the salivary chromosomes of Drosophila to hydrostatic pressure of 1000 atm and found no obvious changes either in form or in chromosomal association. Benteux^674 found that the hydrolysis of starch by various diastases is accelerated at 1500 atm. The activity of pancreatic lipase, proteinase, and pepsin decreases at this pressure, but is restored to normal when the pressure is removed.

CITED LITERATURE

J. Basset et M. A. Macheboeuf, Comptes rendus 195, 1431 (1932). Experiments on the biological action of ultrahigh pressure; the resistance of bacteria, diastases, and toxins to very high pressures.
J. Basset et M. A. Macheboeuf, Comptes rendus 196, 67 (1933). Experiments on the biological action of ultrahigh pressures; the effect of very high pressure on certain antigens and antibodies.
J. Basset, E. Wollman, M. A. Macheboeuf et M. Bardach, Comptes rendus 196, 1138 (1933). Experiments on the biological action of ultrahigh pressure; the action of very high pressure on bacteriophages and invisible viruses.
J. Basset, M. Lisbonne et M. A. Macheboeuf, Comptes rendus 196, 1540 (1933). The action of ultrahigh pressures on the pancreas.
J. Basset u. M. A. Macheboeuf, Ergebnisse d. Enzym for. 1, 304 (1933). Review of results obtained in studies of the effect of ultrahigh pressures on microorganisms and enzymes.
J. Basset, M. A. Macheboeuf et G. Sandor, Comptes rendus 197, 796 (1933). Experiments on the biological action of ultrahigh pressure. The action of very high pressure on proteins.
M. A. Macheboeuf, J. Basset u. G. Levy, Ann. Physiol. Physicochim. Biol. 9, 713 (1933). The action of very high pressure on enzymes.
J. Basset, M. Macheboeuf et J. Perez, Comptes rendus 200, 496 (1935). Experiments on the biological action of ultrahigh pressure; change in the antigenic specificity of serum under the influence of very high pressure.
J. Basset, E. Wollman, F. Wollman et M. A. Macheboeuf, Comptes rendus 200, 1072 (1935). Experiments on the biological action of high pressure. The action of high pressure on bacteriophages, spores, and autolysins.
J. Basset, E. Wollman, M. A. Macheboeuf et M. Bardach, Comptes rendus 200, 1247 (1935). Experiments on the biological action of ultrahigh pressure: the action of pressure on tumors.
J. Basset, S. Nicolau et M. A. Macheboeuf, Comptes rendus 200, 1882 (1935). The action of ultrahigh pressure on the pathogenic activity of certain viruses.
P. Lépine, J. Basset et M. Macheboeuf, Comptes rendus S-té de Biol. 71, 202 (1936). The action of pressure on the virus of fowl plague. Antigenic capacity of a virus subjected to the action of ultrahigh pressure.
M. A. Macheboeuf et J. Basset, Bull. S-té de Biol. 13, 181 (1936). Biochemical and biological investigations carried out at ultrahigh pressures.

E. Wollman, M. A. Macheboeuf, M. Bardachet J. Basset, Comptes rendus, S-té de Biol. 123, 588 (1934). The action of ultrahigh pressure on two rabbit tumors: Brown–Pearce carcinoma and Shope papilloma.
J. Basset, M. A. Macheboeuf et E. Wollman, Ann. Inst. Pasteur 58, 58 (1937). The influence of pressure on pathogenic organisms and their toxins, on viruses, bacteriophages, and malignant tumors.
J. Basset, A. Gratia, M. Macheboeuf a. P. Manil, Proc. Soc. Exp. Biol. USA. 38, 248 (1938). The action of high pressures on the plant virus (tobacco mosaic).
R. River, H. W. Popp a R. B. Dow, Am. J. Bot. 24, 508 (1937). The influence of high hydrostatic pressure on grain germination.
R. B. Dow, Phys. Rev. 56, 215 (1939). Some interesting biochemical and physical effects of high pressure.
R. B. Dow a. J. E. Matthews, Phil. Mag. (7) 27, 637 (1939). Dezintegration of erythrocytes and denaturation of hemoglobin by high pressure.
R. B. Dow, Penn. State Alumni News, 10—11 (September 1939). Joint work with high pressure.
R. B. Dow, J. E. Matthews, Jr. a. W. T. S. Thorp, Am. J. Physiol. 131, 382 (1940). The influence of high pressure on the physiological activity of insulin.
J. E. Matthews, Jr., R. B. Dow a. A. K. Anderson, J. Biol. Chem. 135, 697 (1940). The influence of high pressure on the activity of pepsin and renin.
F. A. Grant, R. B. Dow a. W. R. Franks, Science 24, 616 (1941). Denaturation of egg albumin by pressure.
M. A. Lauffer a. R. B. Dow, J. Biol. Chem. 140, 509 (1941). Denaturation of the tobacco mosaic virus at high pressures.
Dugald E. S. Brown, J. Cell. Comp. Physiol. 4, 257 (1934). The influence of rapid changes in hydrostatic pressure on the contraction of skeletal musculature.
D. A. Marsland, J. Cell. Comp. Physiol. 12, 575 (1938). The influence of high hydrostatic pressure on the division of egg cells of arbacia.
D. A. Marsland, J. Cell. Comp. Physiol. 13, 15 (1939). Mechanism of cell division. The influence of hydrostatic pressure on the division of egg cells.
D. A. Marsland, J. Cell. Comp. Physiol. 13, 23 (1939). The mechanism of protoplasmic flow. The influence of high hydrostatic pressure on cyclosis in Elodea canadensis.
D. E. Brown, F. H. Johnson a. D. A. Marsland, J. Cell. Comp. Physiol. 20, (October 20, 1942). Dependence of bacterial luminescence on temperature and pressure.
F. H. Johnson, D. Brown a. D. A. Marsland Science 95, 200 (1942). The basic mechanism of the biological action of temperature, pressure, and narcotics.
F. H. Johnson, H. Eyring a. R. W. Williams, J. Cell. Comp. Physiol. 20, 247 (1942). The nature of the inhibition of bacterial luminescence: sulfanilamide, urethane, temperature, and pressure.
F. H. Johnson, D. E. S. Brown a. D. A. Marsland, J. Cell. Comp. Physiol. 20, 269 (1942). Reversal of the action of certain narcotics under pressure.
D. A. Marsland, a. D. F. S. Brown, J. Cell. Comp. Physiol. 20, 295 (1942). The influence of pressure on equilibrated sol–gel, with special references to myosin and other gels of protoplasm.
U. Ebbecke, Arch. Ges. Physiol. 236, 653 (1936). The behavior of paramecia under high pressure.
U. Ebbecke u. O. Hasebring, Arch. Ges. Physiol. 236, 648 (1936). The action of high pressure on marine organisms.

R. Haubrich, Arch. Ges. Physiol. 239, 304 (1937). Resistance of erythrocytes to the action of pressure.
H. J. Deuticke and U. Ebbescke, Zschr. f. Physiol. Chemie 247, 79 (1937). Chemical processes during muscle contraction under pressure.
U. Ebbescke and R. Haubrich, Arch. Ges. Physiol. 243, 34 (1939). Effect of pressure on blood coagulation.
R. Haubrich, Arch. Ges. Physiol. 243, 39 (1939). Cessation of blood coagulation under pressure.
U. Ebbescke, Arch. Ges. Physiol. 243, 43 (1939). Coagulation of plasma in quiescent, stirred, and compressed fluids.
U. Ebbescke and H. Zipf, Arch. Ges. Physiol. 242, 255 (1939). Coagulation of blood under the influence of pressure.
R. Wilson [and] T. C. Poulter, Yowa Acad. Sci. 36, 295 (1929). Biological action of high pressure and its effect on colloids. (My naming. P. B.)
D. J. Lloyd and T. Moran, Proc. Roy. Soc. 147, 382 (1934). Pressure and the behavior of water in proteins. I. Isoelectric gelatin gels.
T. Moran, Dept. Sci. Ind. Research (Brit.) Food Invest. Board, 1935. State of water in tissues.
Mckeen Cattell, Biol. Rev. 11, 441 (1936). Physiological action of pressure.
H. Grundfest, Cold Spring Harbor Symposia Quant. Biol. 4, 179 (1936). Effect of hydrostatic pressure on excitability, recovery, and the potential sequence of the frog nerve.
J. Benthaus, Arch. Ges. Physiol. 239, 107 (1937). Effect of pressure on tissue cultures.
H. J. Deuticke and F. Harren, Zschr. f. Physiol. Chemie 256, 169 (1938). Direction of enzymatic reactions at high pressures.
H. J. Deuticke and O. Hasenbring, Zschr. f. Physiol. Chemie 256, 184 (1938). Chemical processes during isotonic and isometric contraction of musculature occurring under the application of pressure.
O. I. Leipunsky, Zhurn. fiz. khimii 14, 1517 (1940). Coagulation of gelatin under pressure.
I. A. Kitching and Floyd Moser, Biol. Bull. 78, 80 (1940). Reaction of the cortical layer to stimulating substances in the eggs of arbacia. IV. Reaction to chemical and physical irritants in the absence of oxygen and observations of the effect of low partial pressures of oxygen and high hydrostatic pressure on amoeba eggs.
K. Nakasima and M. Ikeda, J. Agr. Chem. Soc. Japan 17, 295 (1941). (In English.) Hydrolysis of proteins at high temperatures and pressures.
D. C. Pease and D. Regnery, J. Cell. Comp. Physiol. 17, 397 (1941). Salivary chromosomes of drosophila subjected to the action of high hydrostatic pressure.
F. Benthaus, Biochem. Zschr. 311, 108 (1942). Effect of high pressure on the activity of digestive enzymes.

Submission history

[v1] 1947

Full Text

Recent Work in the Field of High Pressures*

Contents

The Influence of Pressure on Thermal Effects

1. The Influence of Pressure on Heat Capacity

CITED LITERATURE

2. VARIOUS THERMAL EFFECTS OF HIGH PRESSURE

CITED LITERATURE

ELECTRICAL EFFECTS OF HIGH PRESSURE

1. EFFECT OF PRESSURE ON THE ELECTRICAL RESISTANCE OF SOLIDS

Cited Literature

2. INFLUENCE OF PRESSURE ON THE ELECTRICAL RESISTANCE OF SOLUTIONS

CITED LITERATURE

3. EFFECT OF PRESSURE ON THE DIELECTRIC CONSTANT

CITED LITERATURE

4. VARIOUS ELECTRICAL EFFECTS OF PRESSURE

CITED LITERATURE

MAGNETIC EFFECTS AT HIGH PRESSURE

References Cited

Optical Effects of High Pressure

1. Influence of Pressure on the Refractive Index

References Cited

2. Photographic Processes at High Pressure

CITED LITERATURE

3. VARIOUS OPTICAL EFFECTS AT HIGH PRESSURE

CITED LITERATURE

EFFECT OF PRESSURE ON CHEMICAL REACTIONS

CITED LITERATURE

THE EFFECT OF PRESSURE ON BIOLOGICAL EFFECTS

CITED LITERATURE

Submission history

Access Paper

Citation

Share

Related Papers

Feedback

Recent Work in the Field of High Pressures\*