REFRACTOMETER AND REFRACTOMETRIC METHODS OF RESEARCH IN THE WORKS OF M. V. LOMONOSOV

V. L. Chenakal

Refractometry, as one of the quickest and most convenient methods for studying liquids, crystals, glasses, and other transparent substances by their refractive index, began to enter scientific practice, as is known, only from the end of the nineteenth century. From that time on, the refractometer gained increasingly wide dissemination with every year and, by our time, has become a necessary accessory of every laboratory and every industrial enterprise connected with the manufacture and study of optical glass, natural and synthetic crystals, transparent organic compounds, etc.

Almost none of those who use a refractometer know that the honor of introducing this instrument into the practice of scientific research belongs to the brilliant Russian scientist Mikhail Vasilyevich Lomonosov.

The first experiments in determining the refractive index of transparent bodies were carried out in 1664–1668 by Isaac Newton. In his “Lectures on Optics,” delivered in Cambridge in 1669–1671, he describes a vessel made of glass plates in the form of a prism and a wooden prism with holes bored in it, closed with glass plates; by using them and a special quadrant it was possible to measure the “refractive power” of liquids¹. There too, alongside the description of these instruments, he sets forth the results of his measurement of the “refractive power” of water² and points to its dependence on the density of the water, on the presence in it of “various solutions of minerals extracted from underground places”³.

In his Optics, written, as is known, no later than 1687, Newton devotes a special section to an exposition of the question of the relation between the refractive index of transparent bodies and their density (Proposition X of Part III of the second book)⁴.

Having arrived at the conclusion that “the refractive power of a body is very precisely proportional to the density of the body”⁵, Newton gives in this

section, as confirmation of the thought expressed, a large table of “refracting bodies,” containing, in addition to the refractive indices of the latter, also their specific gravities[^6]. Among these “refracting bodies” in the table, along with many others, are listed: “oil of vitriol, rain water, ... wine spirit, well purified, ... olive oil, linseed oil, spirit of turpentine,” i.e., a whole series of liquid transparent bodies.

Even more definitely than in the Lectures, Newton speaks here of the dependence of the refractive index on the chemical composition of the body. Newton attributed the “refracting power of all bodies” “chiefly, if not wholly, to the sulphureous parts,” which, in his opinion, are present to a greater or lesser degree in all bodies[^7].

Although Newton came close to the conclusion that it might be possible to determine the character of a transparent substance from its refractive index, he nevertheless did not draw this conclusion.

In 1710, a member of the Royal Society, Francis Hauksbee, carried out, on an “apparatus” specially constructed by him for this purpose, measurements of the refractive index of more than forty different liquid substances[^8], among which were various vegetable oils, alcohols, resins, acids, aqueous solutions of salts and alkalis, and much else. Simultaneously with fairly accurate measurements of the refractive index of these substances, Hauksbee, like Newton, also determined the densities of all these liquids. From the refractive indices and densities found, constant refractions were calculated for all these bodies.

This work brought Hauksbee still closer than Newton to the discovery of the refractometric method of analysis of matter, but he too did not make this discovery.

From this work Hauksbee drew only one conclusion, namely that “bodies refract [light] not in proportion to their specific gravity, but according to certain other qualities characteristic of each of them.” “Whether this will depend on its (the body’s.—V. Ch.) excitability,” he says further, “or on some different density or structure of its constituent parts, or on any other properties—I do not undertake to decide.”

After Newton and Hauksbee, Christian Wolff became interested in the question of measuring the refractive index of liquid bodies.

In the period between 1710 and 1722, using Hauksbee’s description of an instrument for determining refraction in liquid bodies, he ordered for himself the same kind of instrument from the Leipzig maker of physical instruments Jacob Leupold.

In the second book of his Useful Experiments of All Kinds, Serving Toward the True Knowledge of Nature and Art, he describes this instrument[^9], accompanying the description with a drawing.

Whether Wolff made any measurements of refractive indices with the aid of this instrument or not is unknown. In none of his subsequent works is there any indication that he used a refractometer.

The idea of the possibility of using the refractive index of transparent “liquid matters” to determine their “composition” first occurred only to Lomonosov.

This happened when, in his own words, he “set about the difficult task of uniting chemistry with physics and geometry.” At that time, as he says, he conceived the idea of using for the indicated purposes “a quadrant devised for determining refractions in chemical transparent bodies.”

Lomonosov undertook the realization of this idea in February 1752. He began this work by developing the design and making “a machine suitable for studying the refraction of rays of light in various liquids,” i.e., in the language of our time, a refractometer.

In the minutes of the Learned Conference of the Academy of Sciences there is the following entry, dated February 14, 1752:

“§ 2. His Excellency Mr. Councillor Lomonosov showed a drawing of a machine suitable for studying the refraction of rays of light in various liquids, and explained it to the honorable academicians. It was resolved to petition the Chancellery of the Academy on this matter, so that it would see to the manufacture of such a machine under the direction of His Excellency the author”^10.

As may be seen from the documents that have come down to us concerning this instrument of Lomonosov, its subsequent history developed as follows.

Three days after the indicated meeting of the Conference of the Academy of Sciences, i.e. on February 17 of the same year 1752, the archivist of the latter, Ivan Ivanovich Stafengagen, by a special “report” informed the Chancellery of the Academy of Sciences of the decision of the “academic assembly” on the necessity of manufacturing “Lomonosov’s machine” and attached to this communication a figure of the “machine”^11.

Having received Stafengagen’s “report,” the Chancellery considered it on the same day and issued the following “determination”:

“On this date archivist Stafengagen declared by report: Mr. Councillor and Professor Lomonosov presented to the academic assembly the figure of a machine by means of which one may learn the refraction of rays of light passing through liquid matters. The gentlemen academicians tested that machine and judged it useful that such a machine for conducting experiments in this matter be made; and moreover they ordered that a report on the aforesaid be submitted to the Chancellery, so that it should be ordered that such a machine, according to the instruction of Mr. Councillor Lomonosov, be made in the Instrument Chamber; and what it is to be like, he [Stafengagen]”

Stafengagen has appended the figure. It has been determined that, according to the figure submitted by him, Mr. Councillor is to have a machine made in the Instrumental Chamber, under the supervision of Mr. Councillor and Professor Lomonosov, by the journeyman Tiryutin, from such wood as Mr. Councillor shall order. The expenditure for that wood, nails, and other things that will be needed for it is to be entered as an expense. When it is made, then it is to be given to him, Mr. Councillor, and a report is to be submitted to the Chancellery stating what it will cost”[^12].

A week later the aforesaid “determination” of the Chancellery was brought to its immediate executor, the instrument journeyman of the Instrumental Chamber of the Academy of Sciences, Filipp Nikitich Tiryutin.

In the “order” sent to the latter on February 24 of the same year, the Chancellery wrote:

“By resolution of the Chancellery of the Academy of Sciences, and upon the report of the archivist Stafengagen, you are ordered to make, according to the figure appended hereto, in the Instrumental Chamber, under the instruction of Mr. Councillor and Professor Lomonosov, a machine from such wood as he, Mr. Councillor, shall order”[^13].

At the same time as this order, the Chancellery also sent an order to Lomonosov, informing him that the manufacture of his “machine” had been entrusted to the journeyman Tiryutin, to whom he was to give the corresponding instructions[^14].

For unknown reasons, the making of Lomonosov’s refractometer by Tiryutin dragged on for more than four years. Its manufacture was completed only on September 13, 1756. On that day “Lomonosov’s machine” was delivered from the Instrumental Chamber to the Chancellery with the following “report”:

“According to the order sent from that Chancellery to master Tiryutin, dated February 24, 1752, No. 315, there has been made in the Instrumental Chamber, for Mr. Councillor Lomonosov, a machine of black overseas wood and of copper, according to the appended drawing, which is herewith submitted”[^15].

Having received the “machine,” the Chancellery immediately sent it to the Conference “for inspection”[^16].

No additional information about this refractometer of Lomonosov has yet been found, although from the documents cited it is evident that at the time there existed not only its description, but even a “figure,” i.e. a drawing or blueprint.

From another document, which will be discussed below, it is known that it was based on the measurement of “a ray entering a transparent body.”

The “inspection” of Lomonosov’s refractometer in the Conference was to take place on September 23, 1756. However, Lomonosov did not come to the meeting of the Conference that day, and the inspection of his “machine” was postponed until the next meeting[^17].

REFRACTOMETRIC METHODS IN LOMONOSOV’S WORKS

At the next meeting of the Conference, held on September 27, the “machine,” in Lomonosov’s presence, was examined by members of the Conference. During this inspection Lomonosov himself established that the “machine had not been made as required” and that, in such a form, it was “inconvenient for observing refractions.” As a result, the assembly passed no “judgment” on the “machine,” leaving this question “for a future time.” Later, however, this question was no longer considered by the Conference.

This circumstance is explained by the fact that, by the time the refractometer was made in the academic workshops, Lomonosov already had his own, and moreover more advanced, refractometer, made by the craftsmen of his own laboratory. The following documents testify to this.

Among Lomonosov’s manuscripts preserved in the Archive of the Academy of Sciences of the USSR there is a fragment of an unfinished work of his entitled: “Nova methodus observandi refractiones radiorum in omni genere pellucidorum corporum,” i.e. “A New Method for Observing the Refraction of Rays in All Kinds of Transparent Bodies”[^18].

Lomonosov begins the exposition of the “New Method” by saying that, having founded his chemical laboratory twelve years earlier, he set himself the task that in it, “in addition to chemical lectures and experiments, by which the composition of bodies is ordinarily investigated, it would be possible to attempt investigations with the aid of the laws of geometry and physics and of new methods of inquiry, in the hope of thereby paving the way toward the composition of physical chemistry.” Further, Lomonosov writes:

“Among the instruments with which I set about the difficult task of uniting chemistry with physics and geometry was also a quadrant, devised for determining refractions in chemical transparent bodies.”

Having then recounted that the “chief hindrance and obstacle” in his work was “the late manufacture of instruments, which for years could not be completed,” and that, while waiting for them, he occupied himself with “the chemistry of glass” and “the study of the nature of colors,” Lomonosov says:

“At that time, while pondering improvements to it (his refractometer.—V. Ch.), another method occurred to me, much easier, requiring less time and more capable of producing a greater number of more accurate experiments, and with the aid of which I performed not a few optical experiments in the chemical laboratory.”

“This method consists in this,” he writes further, “that instead of the ray entering a transparent body, one observes the ray emerging from it…”

V. L. CHENAKAL

At these words the manuscript breaks off.

From the indicated document by Lomonosov it is clear that the idea of using the refractive index of a substance as a means for investigating that substance arose in him soon after the construction of his chemical laboratory, i.e., soon after 1748.

Thus, without waiting for the refractometer ordered from the Academy workshops to be made, Lomonosov made in his own laboratory another, more advanced one, and with its aid carried out measurements of the refractive index of various liquid substances.

The same is attested by yet another document.

In Lomonosov’s notes to the dissertation “Theory of Electricity, Composed According to the Mathematical Method,” there are the following entries:

“53. The experiments made in the laboratory on refraction will all be applied here”[^19].

“94. My experiments on refraction in liquids”[^20].

These entries were made, as is known, in April 1756, i.e., even before Tryutin had finished making Lomonosov’s refractometer. The presence in them of references to results he already had from experiments “on refraction in liquids” shows that he possessed a refractometer even before 1756.

This refractometer, according to Lomonosov’s own testimony, was based not on the principle of measuring “the ray entering a transparent body,” like the first one, made by Tryutin, but on the principle of observing the ray emerging from the liquid under investigation, and was “more capable of producing a greater number of more accurate experiments.”

In the “New Method” Lomonosov writes that his chemical laboratory had been founded “twelve and some years” before. As is known, the chemical laboratory at the Academy of Sciences was founded by Lomonosov in 1748; consequently, this work was written by him in 1760.

The dates found from this work thus show that, having established soon after 1748 the possibility of determining the chemical composition of a transparent liquid substance by its refractive index, and having begun to develop and make the apparatus necessary for practical use of his discovery, Lomonosov occupied himself with this question right up to 1760.

The well-known “Chemical and Optical Notes” of Lomonosov testify that he continued these studies even after 1760.

The entries contained in the latter show that, after setting up an instrument workshop in his own home in 1762, Lomonosov again undertook the making of some new design of refractometer.

The first of these entries, made by Lomonosov in the “Chemical and Optical Notes” in the period between June 25 and September 26, 1762, and representing a plan of the work he intended for his craftsmen, contains the following lines relating to the refractometer:

“Kolotoshin.

1. To finish the machine for refractions. . .”^21.

Since this entry already speaks of the “finishing” of the machine, it follows that its construction had been begun earlier than the time indicated.

In another entry, made by Lomonosov after September 26, 1762, and entitled “Completion,” there is the line:

“5. To finish the machine for refractions”^22.

The name of the master to whom this work was entrusted is not indicated this time in the entry.

The third and last entry of the “Chemical and Optical Notes” concerning the refractometer is found, like the first, in the list of works assigned to masters and reads:

“. . . Kiryushka.

1. To complete the machine for refractions. . .”^23.

As is evident from the entry, after the master Aleksei Ivanovich Kolotoshin, another workshop man—Kirill Matveev—was already engaged in completing this refractometer.

At the time described, i.e., in 1762, the scholar’s instrument workshop was wholly occupied with the construction of Lomonosov’s large single-mirror telescope. Wishing to finish its construction as soon as possible, Lomonosov did not hurry the masters with the “finishing of the machine for refractions.” For this reason, it evidently passed from master to master. It must be thought, however, that its construction was completed.

There is no doubt that in the meager information on Lomonosov’s refractometry which time has preserved for us, there is not a tenth part of what he did in this field.

The circumstance that the question of Lomonosov’s refractometer was discussed three times at meetings of the Conference of the Academy of Sciences—on February 14, 1752, and on September 23 and 27, 1756—testifies that this work of his was well known in its time to scholars, both physicists and chemists.

After Lomonosov’s death, the refractometric method he had created for the study of transparent liquids was forgotten for a long time.

Refractometric studies of transparent liquids were resumed after Lomonosov only more than forty years later.

This work was continued by the English physicist and chemist William Hyde Wollaston.

Devoting much time to practical work in the field of chemistry, Wollaston in 1802 arrived at the same idea that Lomonosov had come to half a century earlier, i.e., the idea of the possibility of using the refractive index of a substance to determine its chemical composition.

On the refractometer he had constructed, he determined the refractive index for more than fifty liquids^24.

In our time, physicists and chemists of all nations widely use refractometry for the analysis of transparent substances; however, nowhere in the literature is it indicated that the father of the latter was the great Russian scientist Lomonosov.

CITED LITERATURE

1. I. Newton, Lectiones opticae, Londini, 1729; И. Ньютон, Lectures on Optics. Translation, commentary, and editing by Academician S. I. Vavilov, Publishing House of the Academy of Sciences of the USSR, L., 1946, pp. 55–57.
2. Ibid., p. 57.
3. Ibid.
4. I. Newton, Opticks. London, 1704; И. Ньютон, Optics. Translated from the third English edition of 1721, with notes by S. I. Vavilov. GIZ, M.—L., 1927, pp. 211–216.
5. Ibid., p. 212.
6. Ibid., p. 213.
7. Ibid., pp. 214–215.
8. Fr. Hauksbee, A Description of the Apparatus for making Experiments on the Refractions of Fluids: With a Table of the Specific Gravities, Angles of Observations, and Ratio of Refractions of several Fluids. “The Philosophical Transaction,” vol. XXVII (1710), pp. 204–207; also Fr. Hauksbee, Physico-Mechanical Experiments on various Subjects. 2. Ed. London, 1719, pp. 289–293.
9. Hr. Wolf, Allerhand nützliche Versuche, dadurch zu genauer Erkäntniss der Natur und Kunst der Weg gebähnet wird... Anderer Theil, Halle, 1722, ss. 477–486.
10. Minutes of the Meetings of the Conference of the Imperial Academy of Sciences from 1725 to 1803, vol. II, SPB, 1899, p. 266.
11. Archive of the Academy of Sciences of the USSR (AAN), fond 3, inventory 1, No. 162, fol. 83.
12. Ibid., fol. 84; ibid., fond 3, inventory 1, No. 521, February 17, 1752.
13. Ibid., fol. 85; ibid., fond 3, inventory 1, No. 1150.
14. Ibid., fol. 85 verso.
15. Ibid., fols. 86, 86 verso.
16. Ibid., fols. 87, 87 verso.
17. Protocols, vol. II, p. 362.
18. AAN, fond 20, inventory 1, No. 3, fols. 227–230.
19. Ibid., fol. 151 verso; “Voprosy filosofii,” 1948, No. 1 (3), pp. 382–383.
20. Ibid., fol. 153 verso; “Voprosy filosofii,” 1948, No. 1 (3), pp. 386–387.
21. Ibid., fond 20, inventory 1, No. 4, fol. 18; M. V. Lomonosov, Works, vol. VII, Publishing House of the Academy of Sciences of the USSR, L., 1934, p. 417.
22. Ibid., fol. 41 verso; Works, vol. VII, p. 442.
23. Ibid., p. 49; Works, vol. VII, p. 449.
24. W. H. Wollaston, A method of examining refractive and dispersive powers by prismatic reflection. The Philosophical Transaction; Vol. 92 (1802) II, pp. 365–380.

Fig. 1. First page of Lomonosov’s manuscript “A New Method for Observing the Refraction of Rays in Transparent Bodies of Every Kind” (Archive of the Academy of Sciences of the USSR).

Fig. 2. Lomonosov’s own drawings of the refraction of light in transparent bodies (Archive of the Academy of Sciences of the USSR).

Fig. 3. A page from Lomonosov’s manuscript “Chemical and Optical Notes,” mentioning his “machine for refraction.” (Archive of the Academy of Sciences of the USSR).