I2O Biological Chemistry. 



Tarbaric acid is a crystalline substance soluble in 

 water and alcohol, but insoluble in ether. The isomeride 

 obtained from argol melts at 167. It forms both normal 

 and acid salts as it is a dibasic acid. An interesting salt 

 is the potassium antimonyl tartrate 

 CH(OH)-COO(SbO) 



CH(OH)-COOK 



which is obtained by heating potassium tartrate with 

 antimonous oxide and water, and is known as " tartar 

 emetic." 



Citric acid CH 2 -COOH 



CH( 



[(OH)-COOH 



CH 2 COOH 



is also an acid which is widely distributed in fruits, and 

 is prepared on a large scale from lemon juice. This is a 

 hydroxyl derivative of a tribasic acid, which contains 

 three carboxyl groups. Its synthesis is somewhat com- 

 plex. When glycerol is treated with hydrochloric acid, 

 under certain conditions, it yields a substance called a-a 

 dichlorhydrin, which on oxidation yields dichloracetone. 

 The relationship of these substances to one another is 

 shown in the following formulae : 

 CH^OH) CH 2 C1 



CH(OH) ox ion io - 



CH 2 (OH) CH 2 C1 CH 2 Cl 



Glycerol. a -a- Dichlorhydrin. Dichloracetone. 



Dichloracetone on treatment with hydrocyanic acid 

 yields, in the usual way, a hydroxy nitrile, in which, by 

 hydrolysis, the CN group can be replaced by the carboxyl 

 group, thus 



