182 TARTARIC ACID. 



acid, obtained from succinic acid, is, however, optically 

 inactive. It differs from similar acids in the fact that 

 it gives a powdery precipitate of potassium bitartrate 

 with a saturated solution of saltpetre and potassium 

 chloride. Heated in the air, it, as well as its salts, 

 diffuses an odor of burnt sugar. It melts at 135, and, 

 at this temperature, without loss of water, is converted 

 into two isomeric, deliquescent acids, metatartaric and 

 isotartaric acids. When more strongly heated, water is 

 given off, and it is transformed into tartaric anhydride 

 C 4 H 4 5 , a white powder, which in contact with water 

 or bases, is gradually reconverted into tartaric acid. 

 Subjected to dry distillation, it is resolved into pyruvic 

 (p. 175) and pyrotartaric acids (p. 162), secondary pro- 

 ducts being formed at the same time. Hydriodic acid 

 (phosphorus iodide and water) reduces it to malic and 

 succinic acids. 



Potasssium tartrate. The neutral salt, C 4 H 4 6 K 2 , 

 forms large, very soluble crystals. The acid salt, 

 C 4 H 4 6 .HK (tartar), is deposited in an impure condition 

 in wine casks, in the form of gray or dirty red crusts. 

 The pure salt forms small, transparent, weakly acid- 

 tasting, very difficultly (in 240 parts cold water) soluble 

 crystals, or white crystalline crusts. 



Sodium tartrate. The neutral salt, C 4 H 4 6 ]Sra 2 -f 

 2H 2 0, and the acid salt, C 4 H 4 6 HNa + H 2 0, are both 

 crystallizable, the latter much more soluble than 

 tartar. 



Potassium-sodium tartrate (Seignette salt), 

 C 4 H 4 6 !Osra -f 4H 2 0, results from saturating cream of 

 tartar with sodium carbonate. Large crystals, easily 

 soluble, stable in the air. 



Calcium tartrate, C 4 H 4 6 Ca + 4H 2 0, occurs in a 

 number of plants, also in grape-juice, hence often 

 found in crystals on crude tartar. Formed by double 

 decomposition: a white crystalline powder, scarcely 

 soluble in water, easily soluble in alkalies, acetic acid, 



