154 OXALIC ACID. 



those of the alkalies, are very difficultly soluble in 

 water, but soluble in mineral acids. 



Potassium oxalate. The neutral salt C 2 4 K 2 + H 2 

 forms easily soluble crystals, which effloresce at an ele- 

 vated temperature. The acid salt C 2 4 HK is difficultly 

 soluble in cold water. A still more acid salt C 2 4 HK 

 + C 2 H 2 4 + 2H 2 is the salt-of-sorrel of commerce. 



Ammonium oxalate. The neutral salt C 2 4 (N"H 4 ) 2 

 4- IPO, long prismatic crystals, easily soluble in cold 

 water, is decomposed at a high temperature, forming 

 oxamide, carbonic anhydride, carbonic oxide, ammonia, 

 and hydrocyanic acid. The add salt C 2 4 H(KH 4 ) + H 2 0, 

 prisms, more difficultly soluble than the neutral salt ; 

 when heated, yields oxamic acid. 



Calcium oxalate, C 2 4 Ca+H 2 0. A crystalline 

 powder, insoluble in water. When allowed to crystal- 

 lize slowly, it combines with three molecules of water 

 of crystallization. It can only be obtained in an anhy- 

 drous state by heating it above 200, and it then re- 

 absorbs one molecule very rapidly, when exposed to the 

 air. 



Lead oxalate, C 2 4 Pb. "White precipitate, insolu- 

 ble in water. Silver oxalate C 2 4 Ag 2 . White powder, 

 insoluble in water. Detonates when heated. 



Methyl oxalate, C 2 4 (CH 3 ) 2 , is produced by the 

 distillation of acid potassium oxalate (2 parts) with a 

 mixture of methyl alcohol (1 part) and concentrated 

 sulphuric acid (1 part). Colorless, rhomboidal plates, of 

 a weak odor, fusing point, 51 ; boiling point, 162 ; 

 soluble in water and alcohol ; is decomposed, however, 

 by water, particularly rapidly with the aid of heat, 

 yielding oxalic acid and methyl alcohol. With aqueous 

 ammonia, it yields oxamide and methyl alcohol ; with 

 dry ammonia, methyl oxamate. The ethers of oxyiso- 

 butyric acid (p. 151) and isoleucic acid (p. 152) are 

 formed by the action of zinc on a mixture of this ether 



