boiling the sirup in a close vessel with alcohol at 36° [0.868.]

"The matter on which the alcohol had no action, and which was found in the most perfect sirup to the quantity of two tenths, was very viscous. Being dried and powdered, it exhibited all the characters of gum arabic, namely, its solubility in cold water, forming a thick mucilage, insoluble in alcohol.

"The only character, that appears to distinguish this matter from gum arabic, is its not forming mucous acid with nitric acid.

"It has been asserted, however, that the gummy matter precipitated from sirup of starch is a compound of starch, water, and sulphuric

acid.

"To satisfy himself on this head, Mr. Vogel poured a small portion of alcohol into sirup of starch. The precipitate first formed was composed of sulphate of lime and gum. When this was separated, he poured more alcohol into the sirup that had been decanted from it. The second precipitate was gummy matter, unmixed with sulphate: its solution in water was no longer rendered turbid by muriate of barytes.

"The author, however, was not content with this experiment: for it might be objected to him, that the sulphuric aid, being chemically combined with the gum, would not quit it to unite with the ba. rytes. He dissolved this gum therefore in barytes water evaporated to dryness, and gave the mass a strong red heat in a platina crucible: thus the sulphuric acid should have been set free, and no doubt would have seized on the barytes. Besides, this sulphate would have been decomposed by the carbon of the gum,

and converted into a sulphuret: but muriatic acid poured on the calcined matter extricated nothing but carbonic acid gas, and not an atom of sulphuretted hidrogen gas that could be rendered sensible by paper impregnated with acetate of lead.

Besides, the gum distilled on an open fire did not give out any sulphurous acid, or sulphuretted hidrogen gas.

"It is not therefore a hydrate of starch combined with sulphuric acid; which affords us a fresh proof, that we must take care not to frame hypothesis before we consult experiment.

"He made the same trials with the sirup deprived of gum by alcohol, which did not precipitate the muriate of barytes; but he could not discover in it the least trace of combined sulphuric acid.

"These experiments could not fail gradually to lead to an examination of the action of acids diluted with water on some other substances. Sugar of milk first drew his attention; and with the greater reason, as we have already announced this substance to become more soluble in water after it has been treated with acid.

"Mr. Vogel boiled 100 gr. [1545 grs.] of sugar of milk with 400 gr. of water, and 2 gr. of sulphuric acid at 56 [1·631], for three hours, adding more water as it evaporated. After having saturated the excess of acid by carbonate of lime, he filtered.

"The liquid, though clear, was slightly coloured. Evaporated slowly in a stove, a thick brownish sirup remained, which concreted into a crystalline mass at the expiration of a few days.

"This matter resembling soft

sugar

taste than the most concentrated aqueous solution of sugar of milk. From this extremely saccharine taste the author was led to suspect, that a real sugar had been formed, capable of giving rise to the alcoholic fermentation.

"In fact this product mixed with yeast diluted with water was scarcely placed in favourable circumstances for the alcoholic fermentation, before it commenced in a very brisk manner; though sugar of milk never ferments, as is well known to all chemists, and has been recently placed beyond all doubt by the numerous experiments of Mr. Bucholz.

"This fermented liquor yielded a considerable quantity of alcohol. On varying the proportions of sulphuric acid to three, four, and even five hundredths, very saccharine crystals, that ran into fermentation with extreme facility, were constantly obtained, particularly with five hundredths of acid.

"With two or with four hundredths of nitric acid the sugar of milk could not be converted into a fermentable sugar.

"Three grammes [4.63 grs.] of muriatic acid converted the sugar of milk into a very saccharine sirup capable of the alcoholic fermentation; while 2 gr. [30.89 grs.] of radical vinegar made no alteration in the sugar of milk.

"All these sirups reduced to the crystalline state differ from sugar of milk, not only in being susceptible of the alcoholic fermentation, but also in being very soluble in alcohol, a property that sugar of milk does not possess. Evaporated to dryness by a gentle fire, a white, granular, and extremely saccharine mass is the result.

serve.

"Many are disposed to adopt the opinion, that sugar exists ready, formed in starch, and that the sulphuric acid only dissolves or destroys the principle that holds it enchained.

"It is obvious, that this reasoning is in a considerable degree vague; and besides, that it is founded on no experiment, direct or indirect. In this hyposhesis too we must imagine a compound altogether new, sugar combined with a substance that renders it insoluble in cold water; and sugar has never yet presented us with such a compound.

"Others have supposed, that heat alone is capable of effecting this conversion of fecula into saccharine matter; a fact which, if it were confirmed, might throw fresh light on the saccharine fermentation. of Foureroy.

"Accordingly starch has been boiled with water four days in suc-. cession, till it became extremely fluid.

The filtered liquor was eva-. porated, and the result was a thick mucilage, very bitter, without the least taste of sugar. The starch remaining on the filter resisted the action of boiling water, and exhibited a very hard horny matter.

"It remains to be examined, therefore, whether the sulphuric a-.

cid,

cid, or the starch itself, be decomposed.

"To judge by the letter from Petersburgh, the Russian chemists seem to suppose, that a decomposition of the sulphuric acid takes place.

"To account for these phenomena, we should operate in close vessels. Accordingly, the author introduced into a tubulated receiver a hundred grammes of sugar of milk, four of sulphuric acid, and four hundred of water. To the neck of the retort was adapted a tubulated receiver, from which proceeded a sigmoid tube, opening under a jar filled with water.

"After boiling for three hours, no gas had come over, except the air contained in the vessels. A piece of blue paper introduced into the neck of the retort was not reddened, The water that had passed into the receiver was without taste, did not redden litmus paper, had no smell of sulphurous acid, and did not precipitate lime-water, muriate of barytes, or acetate of lead; consequently it contained no sulphurous, sulphuric, acetic, or carbonic acid; in short, it was nothing but pure water.

"Barytes-water traversed by the bubbles, extricated during the process, was not rendered turbid in the least, and the gas that had passed into the jars was nothing but the air of the vessels.

"It is evident, that the sulphuric acid had not undergone the slightest decomposition: nevertheless, the sugar of milk was decomposed; it had a much more saccharine taste, and after saturation with chalk it fermented very readily with yeast.

"It was necessary, therefore, to examine the decomposing action of

the sulphuric acid on the substantel in question. For this purpose he same experiment was be un afre in close vessels, with 100 grains of sugar of milk, 400 grains of water, and 4 grs of sulphuric acid. During the process no gas was e volved, as in the preceding experi

tant.

"The liquid was then concen trated in a dish accurately weighed, after having added 5 grs of potask to saturate the acid.

"The mass thus evaporated to dryness should have weighed 109 grs in consequence of the 100 grs, of sugar of milk, 4 grs. of sulphu ric acid, and 5 grs. of potash employed: but it weighed only 98 grs. consequently there was a loss of 11 grs. This experiment was repeated twice more, and there was still a loss of 9 or 11 grs. giving a mean of 10 grs.

"This loss is too great to be ašcribed to any error in the weighing, which was conducted with the greatest care.

"Hence we must conclude, that this diminution of weight is oceasioned by a quantity of water formed at the expense of the sugar of milk; and this with the more reason, as no gas, nó acid, and no other volatile substance, was extricated during the boiling.

"All these experiments with the sugar of milk were equally repeated with starch, except that a much larger quantity of water was added to prevent it from burning. The results were the same as those obe tained with sugar of milk.

"Conclusions.

"From all that has been said, it follows:

“ 1. That starch and the feeufs of

of potatoes, boiled with water acidulated with sulphuric acid, are converted into a liquid saccharine matter, the quantity of which corresponds with the weight of the starch employed.

"2. That this saccharine matter is susceptible of the alcoholic fermentation.

"3. That the sirup of starch is composed of gummy matter and saccharine matter in variable proportions.

"4. That the sirup evaporated slowly in a stove exhibits an elastic substance, perfectly transparent.

"5. That the gummy matter exhibits all the characters of a true gum, except that of forming mucous acid by means of the nitric.

"6. That neither this gum, nor the saccharine matter, holds sulphuric acid in combination.

"7. That the heat of boiling water alone is insufficient to convert starch into saccharine matter, as nothing is obtained but a bitter matter, and a horny substance insoluble in boiling water.

"8. That sugar of milk treated with two, three, four, or five hundredths of sulphuric acid is converted into confused crystals, which have an extremely saccharine taste, and are susceptible of the alcholic fermentation.

9. That this saccharine matter does not contain any sulphuric acid in combination.

"10. That the muriatic acid'effects the same changes in sugar of milk.

"11. That neither the nitric nor acetic acid converts sugar of milk into fermentable sugar.

"12. That sugar of milk thus converted into fermentable sugar becomes very soluble in alcohol.

"13. That sulphuric acid is not decomposed in its action on starch and sugar of milk and that, from the facts mentioned, it is much more probable, that the acid takes from these substances oxigen and hidrogen in the proportions neces◄ sary to form water.

1812.

CA

POETRY.