484 CHEMISTRY OP ALCOHOLIC FERMENTATION. 



On the basis of his experiments, GAY-LUSSAC (II.) established 

 the equation of fermentation as : 



C 12 H 24 12 - 4 C a ff a O + 2C0. 2 

 Saccharose. Alcohol. Carbon dioxide. 



(The formulas have been rearranged in accordance with the atomic 

 weights now accepted.) He, however, committed the error of 

 giving an inaccurate composition of the sugar ; but this was cor- 

 rected by DUMAS and BOULLAY (I.), who showed that Gay-Lussac's 

 equation was true solely for glucose C 6 H 12 6 = 2C 2 H C + 2C0 2 . As 

 will be set forth more fully on p. 511, saccharose cannot be fei- 

 m en ted until it has taken up a molecule of water. The products 

 of the equation given above would necessarily amount to 48.89 per 

 cent, of carbon dioxide and 51.11 per cent, of alcohol. DUBRUX- 

 FAUT (IV.) obtained in his experiment 45.17 per cent, of carbon 

 dioxide and 46.15 per cent, of alcohol, and demonstrated that the 

 theoretical yield of both products was unattainable. 



PASTEUR (XXXI.) prepared the way for more precise investi- 

 gation by showing the constant appearance of by-products in 

 alcoholic fermentation, whilst a portion of the sugar is consumed 

 in building up the cell-substance. ELIOX (V.) proved that yeast 

 assimilates sugar during fermentation, which sugar is not trans- 

 formed into fermentation products. According to WORTMANN 

 (XX.) again, about 5 per cent, of the sugar present is consumed 

 by the yeast, for the elaboration of its own substance and not for 

 fermentation. This latter term, strictly speaking, is connned to 

 the process of decomposition that attacks about 95 per cent, of 

 the sugar; and therefore the full amount of the sugar cannot, in 

 any case, undergo decomposition into alcohol and carbon dioxide. 



It would occupy too much space and weary the reader to 

 recount all the various attempts made to determine quantitatively 

 the main products of fermentation, and we will, therefore, mention 

 only those giving the highest results. Thus, PASTEUR (XXXI.) 

 obtained 46.4 per cent, of carbon dioxide, JODLBAUER (I.) 46.54 per 

 cent., and KOSUTANY (I.) 47.5 per cent.; whilst with regard to 

 alchohol Pasteur obtained 48.3 per cent., Jodlbauer 48.67 per 

 cent,, and Kosutany 47.5-48.08 per cent. Hence, in the most 

 favourable instances, the proportion of the theoretical yield 

 amounted to 95.2 per cent, in respect of both alcohol and carbon 

 dioxide ; so that, for the bulk of the sugar decomposed during 

 alcoholic fermentation, the equation 



C 6 H ]2 6 = 2C0. 2 + 2C 2 H 6 



which was not directly challenged by PASTEUR (XXXI.) 

 still holds good. 



We will also consider the case of cell-less fermentation (see 

 p. 464, vol, ii.). BUCHNER and RAPP (IX.), working with 26 grms. 

 of saccharose, obtained 12.2 grms. of carbon dioxide and 12.4 grins. 



