Page:Proceedings of the Royal Society of London Vol 4.djvu/174

Rh The special object of this paper is to show, first, that sugar is not constituted of carbon and water only ; secondly, that during the vinous fermentation water is decomposed; thirdly, that neither pure carbonic acid nor alcohol is, in the common acceptation of the term, the product of this chemical action ; and fourthly, that fermented liquors owe some of their valuable qualities to peculiar products formed during fermentation.

In order to trace the various chemical changes which occur in this part of his research, the author has had recourse to numerous experiments, the details of which are recorded in tabular forms. The first table exhibits the analysis of different kinds of sugar, honey, treacle, grape-juice and extract of malt and hops, the general result of which is that all these compounds contain oxygen in excess above the proportion in which it exists in water, and that they also con- tain a small quantity of nitrogen. He shows, by two independent modes of experimenting, that these bodies, when in solution, can- not be the only compounds undergoing decomposition during that fermentation, which has for its product spirit and carbonic acid; and iu proof of this proposition he recapitulates the different elements in the compounds at the commencement and at the conclusion of the experiments. He finds that when the proximate elements are made the subject of calculation, the weight of the alcohol (consti- tuted of two equivalents of carbon, three of hydrogen and one of oxygen) added to that of the carbonic acid and undecomposed sugar, exceeds the weight of the sugar employed by about 7 per cent. On recapitulating the ultimate elements, he finds that the hydro- gen and the oxygen in the compounds after the fermentation ex- ceed their quantity in the sugar experimented upon, by 15 per cent, of the former, and nearly 14 per cent, of the latter ; and as a proof that no material error is occasioned by the mode of experimenting, it is found that the difference between the quantity of carbon at the first and at the last is very small.

Having arrived at these conclusions, the author infers from his experiments that the water of solution is decomposed by the carbon of the dissolved vegetable matter, in every case of the vinous fer- mentation, and in proportions proximately represented by the fol- lowing formulae : viz.

2 equWalents of the carbon of sugar.. . 6-12 12-24^4.24 olefiantgas..

2 equivalents of the hydrogen of the water !• 2* 3 °

1 equivalent of the carbon of the sugar... 6-12 6-12 f 22-12 carbonic acid.

2 equivalents of the oxygen of the water... 8* 16-5

This decomposition he conceives is brought about by the influence of nitrogen, a very small quantity of which enters into the constitu- tion of the olefiant gas, forming the base of all spirituous fluids of the alcohol and ethereal kind ; and thus each compound experi- mented upon, forms these products in proportion to the quantity of carbon which undergoes chemical change, whether that compound be sugar, soluble parts of malt, grape-juice, or any other body.

The author proceeds to inquire into the constitution of the pro-