950 ORGANIC ACIDS. 



larger quantity by the distillation of acid tartrate of potash 

 (Weniselos). 



PARATARTARIC (RACEMIC) ACID. 



Liebig assigns to this acid, dried at 2 1 2% the formula HO 

 + C 4 H 2 O 5 , which contains half the number of atoms in tartaric 

 acid, and considers the former as a monobasic acid, while tar- 

 taric acid is bibasic. By this difference, the isomerism of these 

 two acids (page 157) is accounted for. Crystallized paratartaric 

 acid contains an additional atom of water, and is represented 

 by HO,C 4 H 2 O 5 + HO. 



Paratartaric acid was discovered by Mr. Kestner, of Thann, 

 and particularly studied by John, by Gay-Lussac and Berzelius. 

 It forms no double salt of potash and soda, analogous to Ro- 

 chelle salt, and is probably on that account monobasic. Para- 

 tataric acid is contained in the cream of tartar of the wines of the 

 Vosges, and perhaps other localities, and is separated by neu- 

 tralising that salt with carbonate of soda, and crystallizing out 

 the tartrate of potash and soda. The mother liquor is precipi- 

 tated by chloride of calcium, and the mixed tartrate and para- 

 tartrate of lime decomposed by sulphuric acid ; on concentrating, 

 the paratartaric acid crystallizes before the tartaric, being con- 

 siderably less soluble. 



Paratartaric acid crystallizes in oblique prisms, of a rhombic 

 base, which effloresce in dry air. It is a more powerful acid 

 than tartaric, decomposing nitrate and sulphate of lime and 

 chloride of calcium, with precipitation of paratartrate of lime. 

 Hence paratartaric acid was first mistaken for oxalic acid. The 

 paratartrate of lime so formed, dissolves in hydrochloric acid, 

 and is precipitated by ammonia. 



Paratartrates. These salts are identical in composition with 

 the tartrates of the same base, but only a few of them have 

 been examined. Paratartrate of lead is an insoluble white 

 powder. Paratartrate of antimony and potash is prepared in 

 the same way as tartar emetic, and has the same composition, 

 but differs in crystalline form, being in four-sided prisms, of a 

 rhombic base, or in needles grouped about a centre. Paratar- 

 taric acid has little disposition to form double salts. 



According to the observations of Fremy, crystallized para- 



