Prof. S. V. Lebedev.

Drying of Refined Sugar at Low Temperatures and Some Related Conclusions Regarding the Permissible Moisture Content Standard for Refined Sugar

(From the Laboratory of Chemical Technology of Food Substances of the Tomsk Technological Institute).

Upon receipt in Siberia of refined sugar transported by rail, during the winter of 1924–25 there were repeatedly observed losses in the weight of the refined sugar, despite the complete soundness at the destinations both of its packing and of the wagons in which it was transported. Alongside this, there were also shipments in which the refined sugar being transported exactly retained the weight established before its dispatch when loaded into the wagons.

To clarify the causes of such an undesirable loss of weight, which in individual cases reached 20 kg and more per wagon, as observed in Siberia by the offices of the “Transport” Society in Troitskosavsk, Kurgan, Chelyabinsk, Sverdlovsk, Petropavlovsk, Omsk, Novonikolaevsk, Tomsk, Krasnoyarsk, and Irkutsk, a Commission was organized consisting of representatives of the railway, the Transport Society, and an expert specialist in the person of the author of the present article. On March 16, 1925, at Tomsk I station, the said Commission:

1) accepted the lump refined sugar that had arrived in four covered wagons, which proved to be entirely sound, shipped from the railway station Timashevsk from the Proletarsky (formerly Timashevsky) sugar-refining factory on February 16, 19, and 20, 1925;

2) established the soundness of the sacks in which the sugar was packed;

3) checked the weight of the arriving cargo and established, wagon by wagon, the presence and magnitude of the loss of weight in comparison with that indicated at dispatch;

4) selected samples of the refined sugar for moisture analysis and transferred them for testing to the laboratory of food substances of the Tomsk Technological Institute.

The weight of the cargo of each wagon was determined by five weighings, using previously checked station scales with a lifting capacity of 250 poods. Samples were taken separately for each wagon from various places of loading and from various sacks that filled the given wagon. Each sample was placed in a separate glass jar with a ground-glass stopper, on which were recorded the wagon number, the number and numbers of the sacks taken, and their location in the wagon (top, bottom, outer, middle, near the door, etc.). Some samples were taken as averages for several neighboring sacks; others were taken individually for one or another sack. In addition, from individual sacks one sample was taken from the outer layers of the sugar and another from its middle. There were also average samples for the whole mass of sugar filling the sack.

A total of 29 samples were taken.

Unloading of each wagon inevitably had to be begun and carried out before the presence and magnitude of the loss in weight of its entire load had been ascertained.

In view of this, and also for completeness of coverage in the general treatment of the matter, it seemed desirable, for each new car, to vary somewhat the procedure for selecting sacks from the total mass for taking from them the sugar going into the individual samples taken from the given car.

The actual determination of the moisture content of the sugar under test was carried out in the above-mentioned laboratory by drying, initially for two hours at 65–70°C, and then finally at 110°C. The total loss in weight of the sugar in the lot under consideration was expressed by car as follows: car I—6 kg, car II—0 kg, car IV—8 kg. The established loss in weight in the lot received proved to be quite varied for the individual cars. This, together with the presence of a car that had precisely preserved the weight of its cargo after transportation, was a favorable circumstance for clarifying the question posed. However, quantitatively the loss in weight in this shipment proved to be considerably smaller than had occurred previously. To clarify this, Table I is given below, presenting the relevant data concerning certain lots of sugar that arrived in Tomsk with a more or less substantial loss in weight.

Table I.

Upon the receipt and inspection by the said commission of four cars of refined sugar that had arrived in Tomsk and were unloaded on March 16, 1925, it was established that in external appearance this refined sugar (lump sugar) was entirely of good quality. Its moisture content, however, as determined at the Tomsk Technological Institute, is presented in the analysis data given below, grouped for each separate car in a separate table. Table II gives a summary of analyses of sugar samples from car I, in which a loss in weight of 6 kg was established for the entire carload.

Table II.

The data in Table II indicate that the moisture content of the refined sugar in car I is generally high and, in individual samples, exceeds the permissible limits for the moisture content of refined sugar according to the Instructions for Chemists of Sugar-Refining Plants by Mintz and Reiser, published by Sakharotrest; under the technical standards indicated there, the upper limit of moisture content in refined sugar is set at 0.3% of its weight.

According to the analyses given in Table II, a certain discrepancy is observed in the moisture content of separate analogous samples of refined sugar, occurring between Nos. 5 and 6, on the one hand, and Nos. 7 and 8, on the other. The reasons for this apparently lie in the individual moisture content of the sugar in each separate sack, which may depend on the nonuniformity, with respect to moisture, of the sugar distributed among the various sacks.

A comparison of the moisture content of the outer and inner layers in individual sacks indicates drying of the sugar transported in car I. This drying and its degree, judging by the analyses, depend on the position of the sacks in the car. In this respect, the upper and lower sacks dry more than the inner sacks. Thus, for car I, the loss of weight is determined by drying of the sugar en route, which, apparently, is connected with the high moisture content of the refined sugar, exceeding the permissible standards.

Analysis of the refined sugar from car II, with the full weight of its cargo at the place of receipt, gave the following laboratory test results, presented in Table III.

Table III.

The analyses presented reveal, for car II, a generally low moisture content, amounting, for the average samples of the middle sacks of the car, to 0.11–0.14%, and for the individual samples falling to 0.02–0.07% by weight. At the same time, no definite relationship is observed between the moisture content of the outer and inner layers of sugar filling the sacks of the car II under consideration.

This may be seen from a comparison of the analyses of samples Nos. 11, 12, 13, and 14. Moreover, it turns out that in one case the moisture content of the inner layers of sugar filling individual sacks is greater than the moisture content of their outer layers, while in another case the reverse is true. In general, the data of Table III indicate that, with considerable dryness of the sugar—in the present case down to 0.14% water and below—the individual moisture content of lump refined sugar in separate sacks is firmly maintained over time. At the same time, prolonged proximity and mutual contact of masses of refined sugar of different moisture content (from 0.02 to 0.14%), as well as contact with the external air under the conditions of transport of the cars under consideration, do not exert any noticeable equalizing influence on the moisture content of the contacting individual sacks of lump refined sugar. Thus, the dryness of the sugar in car II precluded the possibility of its drying out en route and thereby ensured a stable preservation of weight during transportation, in connection with which the weight of the load in this car did not change at all before reaching its destination.

The sugar in car III, with respect to moisture content throughout its mass, is fairly uniform and sufficiently dry. The highest moisture content reaches 0.16%, the lowest 0.04%. In general, the moisture content of the sugar is almost the same as in the preceding car, though still somewhat higher. In connection with this there is already a very slight loss of weight during transportation, amounting to three kilograms per car. Table IV gives data characterizing the moisture content of the refined sugar in car III.

Table IV.

When car IV was unloaded and the lump refined sugar packed in sacks that was in it was inspected, it was found that some of these sacks were somewhat damp in places. A group of such sacks proved to be located in the middle of the load filling the car. The upper and side outer rows of sacks were dry. Given the established complete soundness of the car, which excluded the possibility of wetting en route, and given that analysis showed the sugar in these sacks to be unconditionally dry, the observed external dampness of the latter could have been only the result of some accidental circumstances preceding the loading of the sacks into the car. The analysis of the refined sugar from car IV is presented by the data of Table V, given below.

Table V.

The sugar of car IV attracts attention because of the very great inhomogeneity in moisture content, ranging from 0.04% to 0.33%, with the maximum exceeding the limit permissible for refined sugar according to the technical standards of the above-mentioned “Instructions” issued by the Sugar Trust. Owing to the considerable inhomogeneity of the sugar with respect to moisture, it is not possible, in the case of this car, to trace the influence of the position of the sacks in the car on drying en route. The analysis of sugar from sacks damp on the surface, separated into two special groups, is represented by samples Nos. 28 and 29. The data of these analyses show that the sugar contained in these sacks proves, in the technical sense, to be dry, and moreover with a very low moisture content, corresponding to 0.06–0.07%.

This sugar is the same as that found in most of the other sacks of the car under consideration. As is seen from the analysis of samples Nos. 25, 26, and 27, this sugar, predominant in car IV, has a minimal moisture content of 0.04–0.05%. However, alongside it, as shown by the analyses of Nos. 23 and 24 of Table V, there is also another sugar here—with high moisture—from 0.20 to 0.33%. The presence of the latter in the car is the first cause of the drying of the sugar en route. The second cause, possibly of greater quantitative importance, is determined by the presence in the car of the above-mentioned externally damp sacks. The circumstance that the sugar filling these sacks was in general quite dry, and that the external dampness of these sacks appeared on each of them only in places and, moreover, on only one side, indicates that the sacks in question, before being loaded into the car and probably before weighing, were subjected to slight local wetting from the surface, or else came under snow.

partly retained on them subsequently, and also on the scales, as well as when they were loaded into the wagon. It is obvious that both these, or other analogous causes, by accidentally and temporarily increasing the weight of the sugar loaded into the wagon, during subsequent long transportation must inevitably have led to some reduction in the weight of the sugar that arrived a month later in Tomsk.

In a general summary of everything noted above, the following becomes apparent: 1) the refined sugar of the accepted lot is extremely nonuniform in moisture content, varying from 0.02 to 0.33% by weight; 2) when the moisture content of lump refined sugar is 0.14% or lower, there is no loss of its weight during transportation under the conditions corresponding to the lot under consideration; 3) when the moisture content reaches 0.15–0.16%, a loss in the weight of the transported sugar already appears, amounting to about 3 kg per wagon; 4) when the moisture content is increased to 0.33%, the loss in weight en route increases 2.7-fold in comparison with the preceding case, corresponding to 8 kilograms per wagon.

It is obvious that, in making the indicated comparison concerning the drying-out of sugar in connection with the moisture content of the refined sugar, it is necessary, from the available materials, to exclude IV, where accidental, extraneous circumstances occurred, difficult to account for, connected with the discovery of several wetted sacks in that wagon. In order to draw any general conclusions on the basis of the factual material presented above, one must dwell somewhat on the essence of the phenomenon occurring here, and also on the conditions under which it manifested itself in the case under consideration. In addition, it is necessary to take into account the characteristic properties and peculiarities of the material itself with respect to which the phenomenon of interest to us is manifested.

The products of sugar manufacture, being a mass of sucrose crystallized in anhydrous crystals, in essence ought to be absolutely dry. However, with the technical means at the disposal of modern sugar and refined-sugar factories, and partly for economic reasons, absolute dryness of the products is not achieved. The moisture content of granulated sugar, according to Prof. Zuev, varies from 0.025 to 0.10%, and according to N. N. Rashevsky from 0.10–0.15% by weight. The moisture content of Russian refined sugar, according to Reyser and Ming, under the accepted technical standards should be no higher than 0.3%.

The cause of the moisture content of granulated sugar lies partly in the conditions of its production, and partly in the relatively colossal surface area—from 3.7 to 5.5 sq. meters per 1 kg—which sugar possesses.^1 At the same time, on raw sugar there is retained a layer of molasses of specific gravity 1.45, with a thickness, according to Classen, of 0.10–0.13 mm. Koydl takes this layer of molasses on average as 0.025 mm, but draws attention to the fact that the principal part of the molasses accumulates in the re-entrant angles, always encountered in several crystals that have grown together, where thicker layers are formed, ranging from 0.008 to 0.2 mm. The author has not encountered direct indications of the existence of a layer of molasses and of the thickness of this layer in refined sugar.^2 However, it is easy to approach the solution of this question. In doing so, it should be borne in mind that water in refined sugar may be present both in the form of vapors filling the intercrystalline space of the refined sugar, and in the form of water entering into the composition of the molasses that covers the surface of the sucrose crystals grown together with one another, forming the monolithic mass of the refined sugar. In the following, in considering the question posed, we shall assume: 1) that refined sugar has a moisture content permitted by the technical standards of 0.3% by weight; 2) that the specific gravity of finished cut refined sugar = 1.230, according to Prof. Smolensky;^3 3) that the specific gravity of sucrose = 1.5805 according to

^1 Vogrizhev—Chemistry of the Sugar Industry—p. 414.

^2 Possibly owing to the extreme paucity of special literature in the city of Tomsk over the last 10 years.

^3 Proceedings of the Scientific-Technical Department of Technology of Agricultural Production, Kiev, 1925, vol. II, issue 1, p. 25.

Gerlach’s; 4) that the porosity of loaf refined sugar is 18.7% of its total volume, according to Prof. Smolenskaya¹). It is obvious that the amount of water present in the intercrystalline space of refined sugar in the state of vapor—and moreover of vapor saturating this space—depends on the usual factors determining this, i.e., on pressure and temperature. We shall take the pressure to be normal, while the fluctuations of temperature that occur during the transport of sugar in Siberia are possible within the limits from \(-40^\circ\) to \(+40^\circ\) C. In connection with what has been adopted, the amounts of water vapor saturating the space in 1 cubic meter of air at 760 mm pressure, expressed in kilograms for individual temperatures within the indicated limits, are given by the figures in Table VI below.

Table VI.

Table VII.

If the data of Table VI are referred to the volume of the intercrystalline space of one cubic decimeter of refined sugar, i.e., to 187 cubic centimeters, then we obtain the following amounts of water, expressed by Table VII in grams, in the state of vapor and contained in the pores of refined sugar taken in the indicated volume.

With the specific gravity of refined sugar adopted above, \(d = 1.230\), and with its moisture content of 0.3% by weight, the total content of water in it per one cubic decimeter will be \(1230 \times 0.003 = 3.69\) g. Comparing this figure with the quantities giving the possible maximum water content in the form of vapor in one cubic decimeter of refined sugar, one can see that at \(+20^\circ\) C, the refined sugar no longer contains water in a droplet-liquid state and, thus, proves to be actually dry. It is obvious that, when the temperature of the surrounding atmospheric air rises, an increase in the moisture content of refined sugar, i.e., its drying, will prove completely impossible. The reason is that, as the air is heated, its humidity rapidly increases, becoming higher than the humidity of the air filling the intercrystalline space of the refined sugar. If, for example, the relative humidity of the atmospheric air is 70%, then already at \(30^\circ\) C, judging by Tables VI and VII, it proves more humid than the intercrystalline space of refined sugar with a water content of 0.3% by weight of refined sugar permitted for it by the technical standards. This indicates that the stated standard has been established correctly and that with it the possibility of drying of refined sugar is either almost or even completely excluded. However, this occurs only on the condition that the atmospheric air in contact with such refined sugar

¹) Ibid.

heats it to \(+20^\circ\mathrm{C}\) or higher. Otherwise, i.e. when the air is cooled below \(+20\), the situation changes. In this case the refined sugar under consideration, i.e. with 0.3% moisture, which until then had been dry, becomes damp; moreover, its dampening increases with a further lowering of the temperature. The reason for the noted phenomenon is that, when refined sugar with the indicated content of 0.3% is cooled, the water vapors contained in it at \(+20^\circ\mathrm{C}\) in a state saturating the space begin to condense, gradually precipitating in the form of dew throughout the entire mass of sugar. As a result, a layer of liquid is formed, having, in accordance with the intercrystalline space of the refined sugar, a surface of 3–5 sq. meters per 1 cubic decimeter of refined sugar.

Thus, when refined sugar is cooled below \(+20^\circ\mathrm{C}\), its moisture content does not change quantitatively; however, its form becomes different, since alongside water vapor in the refined sugar there also appears water in a droplet-liquid state. This latter circumstance has its undesirable and understandable consequences. One of them is the drying-out of the refined sugar, although, judging from Table VI, the moisture capacity of cold air falls rapidly as its temperature decreases, and consequently the threat of absorption by atmospheric air of excess moisture from the refined sugar thereby seems gradually to disappear. In reality, however, this possibility is not eliminated even in the case when the temperature around the cooling refined sugar, with a moisture content permissible under present technical standards, drops even to the limits of the most severe Siberian winter frosts. This is due to the fact that, in the intercrystalline space of refined sugar cooled under these conditions, there will be air that is still saturated, at the given temperature, with water vapor, whereas the relative humidity of the atmospheric air does not exceed 60–70%. As a consequence of this, if the sugar and the atmospheric air are in free contact and if the latter can circulate around the refined sugar, there will be a certain absorption by the air of the moisture of the refined sugar and some drying-out of the latter. This phenomenon is noticeably intensified if the temperature of the refined sugar proves to be higher than that of the air surrounding it. In that case the drying-out is manifested the more strongly, the warmer the sugar is in comparison with the air in contact with it. The reason for this is clear: dry cold atmospheric air, warming upon contact with relatively warm refined sugar and increasing its moisture capacity, becomes capable of removing from the sugar its excess moisture under these conditions, and does so the more vigorously the greater the temperature difference between the sugar and the air in contact with it. Naturally, artificial circulation of the air must increase the drying-out of the sugar. Since all the conditions noted here for drying-out of sugar occur in Siberia when refined sugar is transported by rail in winter, this explains the loss of weight—observed repeatedly and already noted above—of refined sugar packed in sacks and shipped in the winter of 1924–26 to Siberia. From what has just been said it also follows that loading warm sugar taken into railcars, for example, directly from the factory and not from warehouses, may also have its negative significance.

In connection with what has been considered, the following proposition emerges: the maximum permissible moisture standard for obtaining dry refined sugar is determined by the amount of water vapor in the state of saturation corresponding to the intercrystalline space of the given refined sugar at the lowest temperature possible for it during storage, transportation, etc. Thus, the highest moisture content for refined sugar that excludes the possibility of its becoming damp upon cooling, in connection with the formation in it of droplet-liquid water, is determined by: the specific gravity of the refined sugar, its porosity, and the lowest temperature possible for the atmospheric air surrounding the given refined sugar. The relation-

linking all this with one another, we obtain equation—1, whence follows equation—2, giving a definite mathematical expression for the greatest moisture content of refined sugar that may be allowed in production:

\[ D \times V \times W_{\max}=P \times V \times St . \tag{1} \]

whence

\[ W_{\max}=\frac{P \times St}{D}\ . \ . \ . \ . \ . \ . \ . \tag{2} \]

where:

\[ \left\{ \begin{array}{ll} D & \text{—specific weight of the refined sugar,}\\ V & \text{—volume of the refined sugar in cubic meters,}\\ W_{\max} & \text{—moisture content of the refined sugar in percent by weight,}\\ P & \text{—porosity of the refined sugar in \% of its total volume,}\\ t & \text{—lowest temperature of the atmospheric air surrounding the refined sugar,}\\ St & \text{—content (in kg) of water vapor in one cubic meter of air saturated with vapor.} \end{array} \right. \]

Substituting in equation 2) the quantities corresponding to the case under consideration, i.e. taking \(D\) equal to 1.230; \(P=0.187\), and successively entering from Table VI the values corresponding to \(St\) for different temperatures, we obtain the numerical values of the maximum moisture content permissible in refined sugar at different temperatures within the limits from \(+30^\circ\) to \(-20^\circ C\). The numerical values thus obtained are presented in Table VIII.

Table VIII.

From the data of Table VIII it follows that the maximum moisture content permissible in refined sugar is not a constant quantity, but changes sharply with a change in the lowest temperature possible for the refined sugar. Of course, apart from temperature, the specific weight of the refined sugar and its porosity also have a known, though smaller, significance; therefore both must be taken into account individually for each grade of sugar. The corresponding numerical values for various grades of refined sugar may be found in the experimental data of Prof. Smolensky, given below in Table IX.

Table IX.

The proposition illustrated by Table VIII has practical significance, indicating that the moisture content of refined sugar shipped to southern countries may be considerably higher than that of sugar sent north. If boxes, barrels, or other air-impermeable packaging are used instead of sacks, this, of course, eliminates the possibility that the refined sugar will dry out, but it does not eliminate the possibility that it will become damp upon cooling. The situation revealed by Table VIII, in connection with the analytical data obtained regarding the moisture content of refined sugar that arrived and was accepted in Tomsk on March 16, 1925, confirms everything stated above and clearly explains the causes of the drying of sugar and the unequal degree of it for the individual cars of the batch under consideration. The reason is that the present standard for the permissible moisture content of refined sugar is not linked with the severe cold of the Siberian winter. From a comparison of the data in Tables I, II, III, and VIII it follows that, for refined sugar shipped in winter to Siberia and in general to northern regions, the maximum moisture content of the refined sugar should not exceed 0.10% by weight, i.e., in this case it should be three times lower than the present standard, which is quite correctly established for the central and southern belt of European Russia and corresponding other climatic regions with a short and comparatively warm winter.

The drying of refined sugar, which is a phenomenon of evaporation of the water contained in it, is to a certain extent explained by the dependence established already by Dalton, who gave a mathematical expression for the rate of evaporation of a liquid—\(v\)—in connection with the various factors determining it. It was found that this rate is proportional to the free surface of the liquid—\(S\), proportional to the difference between the vapor pressure—\(R\)—of the saturated vapors at the temperature of the evaporating liquid and the pressure—\(r\)—of the vapors already present above the liquid. In addition, it is inversely proportional to the pressure—\(H\)—of the foreign gas (in the case under consideration, air) above the liquid. All this leads to the formula¹:

\[ v=\frac{CS}{H}(R-r), \]

where \(C\) is a constant factor depending on the speed of motion of the air or wind. In developing the proposition given by Dalton, Laval established that \(v\) is inversely proportional to \(H^n\), where “\(n\)” is represented by a quantity depending on the nature of the evaporating liquid and on the gas surrounding it; for example, in air for water \(n=1.18\). According to Stefan’s investigations, when a liquid evaporates in vertical tubes in which a layer of saturated vapor is formed over the very surface of the liquid (the case corresponding to the conditions of drying of refined sugar), slowly diffusing toward the open orifice of the tube, the rate of evaporation is inversely proportional to the distance of the liquid level from the open end of the tube.

The dependencies just noted, established by Dalton, Laval, and Stefan, while serving as direct confirmation of what has already been analyzed above regarding the causes, conditions, and degree of drying of refined sugar, also serve as a certain supplement to the conclusions drawn. In this connection, for example, the importance of the size of individual pieces of refined sugar in the process of its drying is brought to the fore. Without going here into a further detailed analysis of the question under consideration, we shall make a summary of the general conclusions to which all the foregoing leads. These conclusions are as follows:

1) Dry refined sugar should be understood as sugar whose moisture content is due only to the presence in it of water vapor.

2) The appearance of water in refined sugar in the drop-liquid state is a sign of its becoming damp.

3) The technical norm for the highest moisture content of refined sugar varies depending on the lowest temperature permissible for the given refined sugar.

4) The technical norm for the highest permissible moisture content in refined sugar—\(Wmax\)—is proportional to the porosity of the refined sugar, expressed in volume percent of it—\(P\), proportional to the content of water vapor in the saturated state in one cubic meter of air \(St\) at the lowest temperature permissible for the given refined sugar—\(t\), and inversely proportional to the specific weight of the refined sugar—\(D\), i.e.

\[ Wmax = \frac{P \times St}{D} \]

5) Lowering the temperature of the refined sugar below that adopted in the calculation for its limiting moisture content leads to the refined sugar becoming damp.

6) Drying of refined sugar in the absence of tight packaging is possible at all temperatures both above and below \(0^\circ\), provided that the sugar is warmer than the surrounding air and the moisture content of the latter is lower than the moisture content of the air filling the pores of the sugar.

7) In order to eliminate the possibility of undesirable dampening and drying of refined sugar, the moisture content permitted for it of 0.3% by weight has been established correctly for the middle and southern belts of European Russia and for analogous climatic regions; however, for refined sugar shipped in winter to more northern regions, where prolonged winter frosts reach \(-20^\circ\) and below, the maximum moisture content of refined sugar should not exceed 0.10% by its weight.

The conclusions drawn are of not only theoretical interest for refined-sugar production, but also of definite practical significance. The fact is that the technical attainability of the present norm for the moisture content of refined sugar, and the obligation to observe it on the grounds of the need to ensure that the product retains its original quality, which is threatened by excessive moisture, lead to production work being conducted toward attaining the maximum dryness of the product released by the factory that is technically attainable. Owing to this, the latter proves under such conditions, in the majority of cases, to be as if overdried, i.e. drier than is required by the present technical norms. In connection with this, control of the moisture content of finished refined sugar is of very little interest to factories and to the factory laboratory, being included among the tasks of ordinary, purely factory sorting of the finished product.

If such a situation is understandable from the production-technical side, whose task is to turn out a product of the highest quality, then from the commercial standpoint it is incorrect, especially now, when the sugar industry of the U.S.S.R. has entered the stage of precise accounting of production, connected with the refinement of the calculation of expenditures, losses, and yields. It is obvious that in this case it would be a mistake to release from the factory refined sugar with a moisture content of 0.02%, if it is possible to release it onto the market as equally good in quality and unquestionably stable in storage with a moisture content of 0.3%. This would be equivalent to reducing the productivity of the factory, for every million poods of refined sugar produced, by 2,800 poods of it. Thus, from the commercial point of view, it is obligatory to maintain in refined sugar not the lowest moisture content technically attainable for the factory, but the highest practically permissible one, ensuring the necessary degree of dryness of the sugar and excluding the possibility of its becoming damp and drying not only in the factory warehouses, but also during shipment to the places of consumption and storage of the refined sugar there. It is obvious that the norm for the moisture content of refined sugar permissible under such conditions is in a certain dependence, already considered above, on the season, on the geographi-

geographical location of the factory, the place where the refined sugar is consumed and stored, as well as on the conditions of packaging, the duration of transport, and, finally, the route by which the refined sugar travels from the factory to the places of its consumption. All these circumstances are easily taken into account in each individual case, and therefore the establishment of the corresponding moisture-content standard for the refined sugar released by a factory cannot encounter any difficulties.

The practical implementation of the indicated standards in production requires only the appropriate analytical control of the moisture content of the refined sugar released, on the part of the factory laboratories, whose activity in this direction will help refined-sugar factories save many thousands of rubles.

1. Physics by Khvolson, Vol. III, p. 481. ↩