74 ORGANIC AGRICULTURAL CHEMISTRY 



in silage, where it is produced by the bacterial fermentation of 

 the carbohydrates present in corn, clover, etc. These carbo- 

 hydrates are cane sugar and glucose which are present as such 

 or have been formed by the hydrolysis of starch. 



The three carbohydrates, cane sugar, milk sugar and glucose, 

 all yield lactic acid by bacterial fermentation. The form of 

 acid obtained, i.e. inactive, dextro or levo, depends upon 

 the particular bacterial organism which produces the fermen- 

 tation. It is probably true that lactic acid is an intermediate 

 product in the alcoholic fermentation of glucose into alcohol. 

 Lactic acid itself undergoes further bacterial fermentation and 

 is converted by the butyric acid ferment into butyric acid, 

 C3H7 - COOH. 



+ O2 

 2 C3H6O3 -> C3H7 - COOH -f 2 CO2 + 2 H2O 



Lactic acid Butyric acid 



When milk sours and lactic acid is formed, it is the lactic 

 acid which causes the coagulation of the protein, casein, present 

 in colloidal suspension in the milk and which forms the coagu- 

 lum or curd from which cheese is made. 



When pure, inactive lactic acid is a colorless, sirupy liquid 

 which absorbs water from the air. It decomposes on heating, 

 forming an inner ester called a lactide. It is used as a mordant 

 in dyeing in the form of the antimony salt. 



Dextro Lactic Acid (Sarco Lactic Acid). — The dextro-ro- 

 tatory variety of lactic acid is the form found in the flesh or 

 muscular tissue of animals, from which it gets its name Sarco 

 lactic acid. It is also found in the blood and urine. It may be 

 prepared by the splitting of the inactive form as previously 

 described, or by bacterial fermentation of the sugars previously 

 mentioned. 



Levo Lactic Acid. — The levo form of lactic acid is ob- 

 tained when cane sugar is fermented with certain lactic acid 

 bacteria. It may also be obtained by splitting the inactive 

 form. 



