LACTIC ACID. 809 



Diastase after being exposed two or three days to humid air 

 undergoes a modification, and acquire the property of trans- 

 forming starch into lactic acid, making it pass probably through 

 the intermediate state of dextrin. Hence malt, slightly 

 moistened and exposed to air for two or three days, when 

 afterwards pounded and placed in water kept at a temperature 

 of from 6*8 to 77; becomes warm, and after a few days, the 

 liquid is found to contain much lactic acid. This is a pure 

 lactic fermentation, without any production of mannite. But 

 animal matters prepared in a similar manner often modify sugar 

 quite differently, very little lactic acid is formed but con- 

 siderable quantities of mannite and the viscid matter. Fre- 

 quently indeed the sugar is wholly changed into alcohol and 

 carbonic acid. The albuminous ferments in different stages of 

 decomposition produce different fermentations. (Annales de 

 Chimie, &c., 3 serie, ii, 257.) 



LACTIC ACID. 



Formula of the acid combined with oxide of zinc : 



C 6 H 5 O 5 =~L; of the hydrated acid HO + C 6 H 5 O 5 =HOL,; 

 of the sublimed acid C 6 H 4 O 4 . 



Other sources of lactic acid, are the whey of milk, in which 

 it is formed while the latter becomes sour, human urine, and 

 probably most other animal fluids, the juice of fermented 

 cabbage or sour-crout, and the fermented extracts of rice and 

 of nux-vomica, the spent ley of tanners, and the sour water 

 of the starch manufacture, from which lactic acid has been 

 prepared for sale. 



The process for lactic acid recommended by Boutron and 

 Fremy consists in mixing 8 or 12 pints of milk, with a solution 

 of 8 or 12 ounces of milk sugar in water, and leaving the liquid 

 exposed to air in an open vessel for several days, between 

 68 and 77. The liquid being now found very acid, is neu- 

 tralised with bicarbonate of soda ; after twenty four or thirty 

 hours, being again acid, it is saturated, and the saturation 

 repeated till all the milk sugar is converted into lactic acid. 

 When it is supposed that the transformation is complete, the 

 milk is boiled to coagulate the caseum ; and the liquid filtered 

 and evaporated to a syrupy consistence, with caution at a 

 moderate temperature. The product of the evaporation is 



