1234 



LACTIC ACIDS. 



As occurring characteristically in muscles it is hence found 

 in large quantities in Liebig's 4 extract of meat, ' which is the 

 most convenient source for its preparation. 



The zinc and calcium salts of sarcolactic acid are much more 

 soluble both in water and alcohol than are those of ethylidene- 

 lactic acid. 



Zinc sarcolactate. Zn(C 3 H 5 O 3 ) 2 + 2H 2 O. Soluble in 17-5 

 parts of water at 15 or 964 parts of boiling 98 p.c. alcohol. 



Calcium sarcolactate. Ca (C 3 H 5 O 3 ) 2 + 4 H 2 O [ ? 4J H 2 O]. 

 Soluble in 12-4 parts of cold water, soluble in all proportions 

 in boiling water or alcohol. 



The free acid is dextrorotatory, but the true value of (a) D is 

 unknown owing to uncertainty as to the purity of the acid. 

 The salts on the other hand are all Isevorotatory. For the zinc 

 salt, when one part is dissolved in 18 of water (a) D = 7-6. 



FIG. 196. ZINC SARCOLACTATK. 

 ( After Kuhne.) 



FIG. 197. CALCIUM SARCOLACTATE. 

 (After Kuhne.) 



Both this acid and the preceding one yield an intense yellow 

 coloration when added to an extremely dilute (almost colourless) 

 solution of ferric chloride. This reaction is sometimes useful. 



The laevorotatory form of this acid which should exist accord- 

 ing to chemical theory has quite recently been obtained by a 

 bacterial fermentation of cane-sugar. Its salts are dextrorota- 

 tory and if equivalent amounts of its zinc salt are mixed with 

 the same laevorotatory salts of sarcolactic acid and warmed for 

 some time, on subsequent crystallization the optically inactive 

 salt is obtained of ordinary lactic acid as it arises during the 

 fermentation of sugars. 



3. Ethylene-lactic acid. CH 2 (OH) . CH 2 . COOH. 



This acid has been usually described as accompanying 

 sarcolactic acid in extracts of muscles and as being isolable 



