49 o CHEMISTRY OF ALCOHOLIC FERMENTATION. 



baryta water or lime water, the carbohydrate yields 50 per cent. 

 of lactic acid, without any production of alcohol, so that the decom- 

 position of lactic acid into alcohol requires the action of the more 

 powerful alkali. If potassium lactate be electrolysed by the 

 KOLBE (I.) method, carbon dioxide and aldehyde are formed ; and, 

 according to Dossios (I.), carbon dioxide and acetic acid are 

 produced when lactic acid is warmed with diluted chromic acid. 

 Now, aldehyde and acetic acid are the simplest of derivatives from 

 alcohol, so that a purely chemical proof is afforded of the presence 

 of the atomic aggregations, carbon dioxide and alcohol, in lactic 

 acid. According to Duclaux, calcium lactate in aqueous solution 

 is decomposed in sunlight and air directly to alcohol, calcium 

 carbonate and calcium acetate ; and Hanriot states that the same 

 salt furnishes large quantities of alcohol and acetone when heated 

 with caustic lime. Maze found that Allescheria (Eurotiopsis) 

 Gayoni (see pp. 348 and 368, vol. ii.), also produces alcohol when 

 grown in a nutrient solution containing lactic acid. 



323. The Non-volatile By-products of Alcoholic Fer- 

 mentation, Glycerine, Isobutyleneglyeol, Succinie 

 Acid, Oxalic Acid, Lactic Acid. 



In considering the main products of alcoholic fermentation in 

 the preceding paragraph, it was stated that only about 95 per cent. 

 of the total weight of the sugar is converted into alcohol and carbon 

 dioxide. 



LAVOISIER (II.) had already observed the occurrence, in his 

 fermentation experiments, of an organic acid, which he assumed 

 to be acetic acid, corresponding to 2.63 per cent, of the fermented 

 sugar. PASTEUR (XXXI.), however, was the first to emphasise 

 the fact that alcoholic fermentation always results in by- 

 products, the formation of which involves the consumption of 

 about 5-6.5 percent, of the sugar. In 1857 he named succinic 

 acid previously discovered by 0. SCHMIDT (II.) as one of these 

 by-products, and in 1858 discovered glycerine, together with fat, 

 cellulose and other (unnamed) substances. Following up the 

 idea that these substances originated in the sugar, he established 

 the following equation for the decomposition of this latter : 



49C 6 H 12 6 + 3oH 2 = I2C 4 H 6 4 + 72C 3 H 8 O 3 + 3oC0 2 . 

 Glucose. Succinic acid. Glycerine. 



From 100 parts, by weight, of sugar subjected to fermentation, 

 Pasteur obtained 3.607-3.64 parts of glycerine, 0.673-0.76 parts of 

 succinic acid, and 1.2-1.3 parts of other substances. 



With regard to glycerine, it had already been found by 

 BOUSSINGAULT (II.) that no definite relation exists between this 

 and the sugar consumed; and also that yeast itself furnishes 



