Mechanics, Physics, and Chemistry.

In the "Journal für Praktische Chemie," for May, 1843, an essay appeared by Carl Hochstetter, embracing a series of experiments on Sugar, subjected to various actions, and chiefly designed to develope the action of the substances contained in the juice of the Sugar-beet, as well as those with which the Sugar is brought in contact in the course of manufacture. The first part of the essay referring only to the Sugar-beet, we shall confine ourselves to the subsequent portion, which will apply to the manufacture of Sugar generally. J.C.B.

Behavior of pure solutions of Sugar under different actions and circumstances; by CARL HOCHSTETTER. Translated by OEHLSCHLAGER, and communicated to the Journal of the Franklin Institute by Wm. M. Davis.

Both in the tropical and home manufacture of sugar, the sugar obtained by expression, or maceration, is only partially preserved in its original state, that is, as cane-sugar. Even before it had been proved to a certainty, that the sugar-cane, and the beet, contained only cane. sugar, it was admitted that a large portion of the molasses of the sugar refiner, is to be attributed to a change of the cane-sugar under different influences during the process of preparation.

The early fermentation of saccharine vegetable fluids, which have been expressed a phenomenon very common in the manufacture of sugar in the tropics, proves the action of the nitrogenous substances contained in these juices, for, as far as our present experience goes, they alone can produce those changes which we denominate fermentation.

The observation that after the continued boiling of a solution of sugar, only a part can be preserved as sugar fit for crystalization, points out heat as another agent, or influence.

There is no doubt that the influence of such agents diminishes the yield of the refiner; but I doubt whether a correct judgment has been formed of them, and without this, improvements in the manufacture of sugar are not possible.

To obtain this end experiments had to be made on a small scale. These I made by trying to submit solutions of sugar to the influence of the same agents to which the sugar in the juice, and during the whole process of preparation can be submitted.

In consequence of the insufficiency of chemical expedients to separate the newly formed kinds of sugar from the cane-sugar, and to determine their quantity, I found it impossible to ascertain the exact degree of decomposition which I observed under different influences. It is true that more recently the polarization of light has been applied to determine the quantity of the different kinds of sugar in a solution, and the degree of transformation of the sugar under different influences; I, however, did not apply this method, as it could only be of use to me in a few observations, but would be entirely inapplicable for the greater part. I moreover doubted the correctness of the re

sults in these cases, for reasons to which I shall revert hereafter. The results of this method, as given in the works of Ventzke,* and Soubeiran,t I have, however, constantly compared with my own. I.-Influence of atmospheric air upon a pure solution of Sugar, at a common temperature.

Sugar dissolved in pure distilled water can be preserved for weeks in closed vessels, without undergoing any changes; but if, on the contrary, we expose a solution of about 10° B., to the air in a tumbler, and protect it against dust, we find already after three days, traces of altered sugar, which increase daily. This fact had been observed before, and the change in the second case had been attributed to the organic substances contained in the air.

But whatever probabilities may favor this opinion, it would almost appear that the atmospheric air had an immediate share in bringing about these changes, for pure solutions of sugar, a large part of which is exposed to the air, change in a very short time. The following experiment will show this to be correct:

I filled a glass cylinder, open at the top and at the bottom, with broken glass, like an acidulating vessel for the quick vinegar process, and gradually dropped a pure solution of sugar, the purity of which I had before ascertained by the copper test, slowly, and in such manner, into it, that the air found unimpeded access. The liquid running out below, I continued to pour in at the top. The temperature of the surrounding air was 15° R. After six hours labor I found already altered sugar, for, on mixing with it sulphate of copper and alkali oxidule, (protoxide of copper) was separated. This change increased rapidly, and after 36 hours of operation, the decomposition had progressed so far, that, on evaporation under the air-pump, first, no crystalization was obtained, and after many trials, only a very sparing one. The liquid had remained colorless during these trials, but had become somewhat dimmed.

Whether the effect is produced by the influence of the oxygen of the atmospheric air, or by the organic substances, this experiment proves that considerable contact with the atmospheric air, can change a pure solution of sugar.

Influence of heat upon the pure solutions of Sugar in boiling.

A solution of sugar boiled for some time, or exposed to a temperature above boiling water heat, decomposes itself, as has been observed by many, and loses its power of crystalization. At the same time several new substances are formed, such as uncrystalized sugar, by some called sirop sugar, and noticed as a peculiar kind of sugar, formic and acetic acid, ulmic and ulmic acid.

These changes and transformations, under the influence of water and of heat, progress very slowly. To obtain a distinct view of the changes of a solution of sugar in boiling, a continued action of several hours is requisite. Many experiments made on a large scale, almost

* See Journal für Pr. Chemie, vol. xxv, p. 65, and vol. xxviii, p. 101.

† See Journal für Pr. Chemie, vol. xxvii, p. 281.

made me doubt the pretty generally received opinion, that the greatest part of the molasses obtained in the preparation of sugar, is sugar destroyed by heat. The previous experiments, where sugar solutions had been boiled for twenty-four hours and more, could not be considered as a practical standard; I therefore made the following experiments several times:

A solution of pure sugar of 25° B., I boiled in an open bowl at one trial for 1 hour, at another for 1 hour, and at a third for 2 hours, and in such a manner that the evaporated water was not replaced until the temperature of the boiling mass had reached 110°-112°C. Even after two hours boiling in this manner, the mass remained colorless; left under the air-pump for crystalization it proved very copious. The liquid, after having been separated from the crystals for some time, formed a solid mass; but decomposition had taken place notwithstanding, for the test by copper showed traces of uncrystalized sugar, and when heated with lime-water the liquid changed to a yellow color. This experiment, repeated frequently, always produced the same result. When the solution of sugar is boiled in an alembic, the sugar undergoes a greater change than in the bowl; the time that the sugar is under the influence of heat being the same. It is difficult to account for this, for we might more readily suppose, that, as the air finds freer access to the bowl than to the alembic, the contrary would be the case. Perhaps this difference of behaviour, when boiling in the alembic, is caused by the flowing back of the water of condensation, which itself aids in the decomposition of the sugar through fermic acid, which cannot be known by any test.

This may be the cause that Soubeiran, in his experiments, after the effect of a boiling heat of two or three hours, discovered considerable decomposition. In boiling sugar for a longer time, it becomes evident that the decomposition, under a more protracted influence, proceeds. more rapidly than in the beginning of the experiment, because the products formed by the first action, aid in the decomposition of the sugar, and the more of these there are formed, the more will the transformation be accelerated.

According to Soubeiran, a solution of sugar decomposed by boiling, reacts strongly acid, and, in this case, the acceleration of the process of decomposition can easily be explained. I have not been able to ascertain whether a solution of sugar, which had been boiled for a long time in an open bowl, reacted as an acid upon litmus paper, yet there are in this liquid, acid products, which, as soon as alkalies are introduced, immediately destroy the alkaline reaction. Mixed with calcareous earths, we obtain partly indissoluble compounds. The formation of volatile and non-volatile acid products is incontrovertible, and from this we may deduce, that fruit and grape sugar must be formed in the same manner as when acids act upon cane sugar. The opinion that a peculiar kind of sugar is produced by the decomposition of cane sugar, appears to me, therefore, very hazardous. Ventzke calls this sugar sirop sugar, and mentions, as its peculiar * See Journ. für pr. Chemie., vol. xxv, 2nd series, p. 75.

VOL. VII, 3RD SERIES. No. 1.-JANUARY, 1844

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quality, that it does not polarize the light. If we compare the phenomena, which accompany the transformation of sugar during ebulition, with the effects of diluted acids, we shall find considerable analogy, for in both acid products are the result. We may also take it for granted, that as soon as acid products have been formed, they exert their influence in such a manner as to generate fruit and grape sugar, and other productions. The perfect neutrality of the mass of sugar, examined by Ventzke, may, therefore, be accounted for on the principle, that grape sugar and fruit sugar existed in such proportions as mutually to destroy their power of polarization. A separation, or isolation, of these two kinds of sugar has hitherto been found impossible, by crystalization it would scarcely be possible to separate them.

To observe the influence of atmospheric air upon a boiling solution of sugar, a solution of 15° R., was boiled in an alembic, and a continued stream of atmospheric air guided through the boiling liquor, by means of a forcing pump (aspirans.) The influence of the air could not be mistaken here, for in less than one hour and a half the saccharine fluid had become considerably darker. The test by copper indicated a considerable decomposition, and the crystalization of the sugar, under the air-pump, was more difficult, leaving behind a darker colored sirop, than in those experiments where the boiling solution of sugar had not been similarly exposed to the air, for, in boiling in the open air, the generated steam prevents the contact with the air.

These experiments prove that the action of the heat in boiling solutions of sugar on a large scale, under the same circumstances, and during the period of ebulition, produces no observable effect when the solution is pure; but that the action of the oxygen of the air aids materially in effecting a transformation in the cane sugar.

Behaviour of the solutions of Sugar under the influence of Alkalies.

That cane sugar combines with alkalies, that from this combination it can be separated again by acids, without any alteration in its form, is known.

In the manufacture of sugar the combination with lime is of great importance; although it has often been demonstrated that lime stands in the same relation to sugar as all the other alkalies, yet the general opinion that large quantities of lime added to the saccharine vegetable juice destroys the sugar, is still prevalent among a large number of sugar refiners. To ascertain this point, and, at the same time, to obtain a knowledge of the behaviour of alkaline solutions of sugar under the influence of different agents, the following experiments were made:

I prepared sugar lime, by digesting a solution of sugar with caustic lime, at a common temperature, and, after filtering it, I obtained a liquid saturated with lime, and as clear as water; of this I made use in all the subsequent experiments.

When this solution of sugar lime was mixed with carbonic acid, heated to a boiling heat, to drive off the excess of carbonic acid, and the liquid was separated, by filtration, from the carbonate of lime,

which had been formed, I obtained, after evaporation under the airpump, a sugar perfectly pure, which, when dissolved, and the test of copper applied, did not show a sign of decomposition. Another part of this solution of sugar lime I boiled for two hours constantly over a free fire, always supplying the evaporated water; after which time I used carbonic acid in the decomposition, and the sugar made its appearance as in the foregoing experiments. One part of the solution of sugar lime I reduced by evaporation in a china bowl over the lamp, keeping it constantly boiling; the temperature rose to 120° C., (248) Fahr.) As the mass at this point became so thick, that I could not stir it, it was partially burnt, and the smell indicated the products which sugar forms when distilled dry with alkalies; after cooling, the whole mass was hard, so that it could be reduced to a powder. I separated the white pieces from those which had became brown, and had suffered by decomposition; the former dissolved in water without any residuum, and when decomposed with carbonic acid, did not present the least appearance of sugar incapable of crystalization.

These two results agree with the results of Soubeiran, according to which, sugar combined with alkalies resists the effects of heat better than the pure solution of sugar.

When a concentrated solution of sugar lime is for some time exposed to the air, the sugar may also be separated unchanged; but hereby a peculiar phenomenon is observed. The mass gradually attracts carbonic acid from the air, without carbonate of lime being separated as a precipitate; at last the mass becomes transparent like a jelly, and under the air-pump assumes the appearance of a transparent gummy substance. On attempting to dissolve this mass in water, large quantities of carbonate of lime are separated; the same occurs when the moist, jelly-like mass is diluted, or heated, with water.

That a solution of sugar will decompose carbonate of lime, is a known fact, but these quantities are so small, that they cannot be compared with those found in this case. Whenever I tried to dissolve newly precipitated carbonate of lime in concentrated, or diluted, solutions of sugar, or of sugar lime, I always found that only a small portion of the fluid had been absorbed; when I introduced carbonic acid into a solution of sugar lime, a precipitate of carbonate of lime would form immediately.

Why, in the above mentioned case, when the absorption of carbonic acid proceeded very slowly, no carbonate of lime was separated, I am not able to explain; but the phenomenon is interesting enough to be examined more carefully.

Concentrated, or diluted, solutions of sugar lime, which have been a long time exposed to the air, generally become somewhat darker, but even when they assumed the color of white wine, I could never discover decomposed sugar. The color is undoubtedly produced by organic substances, which, introduced from without, have been decomposed by calcareous earths.

Effect of neutral Salts upon the pure solutions of Sugar.

When alkaline chlorides, neutral alkalies, alkaline sulphates, and