226 DERIVATIVES OF CARBONIC ACID. 



potassium mercaptide (p. 54); and by conducting car 

 bon sulphoxide into a cold alcoholic solution of potassa. 

 The free acid cannot be extracted from this salt, be 

 cause it is resolved into carbonic anhydride, alcohol, 

 and sulphuretted hydrogen, the instant it is liberated. 



Carbonyldisulphethyl, CO j g ^g! (isomerie with 



ethyl xanthogenate), is produced by the action of sul 

 phuric acid or hydriodic acid on ethyl sulphocyanate 

 (p. 214). Colorless liquid, boiling at 196-197. With 

 alcoholic potassa, it yields mercaptan and potassium 

 carbonate; with alcoholic ammonia mercaptan and 

 urea. 



Carbamic acid, CIPNO 2 = CO I ^ *p Cannot be 



isolated. ^ The ethers of this acid are formed by the 

 action of ammonia on the ethers of carbonic acid at 

 the ordinary temperature (above 100 urea is formed); 

 by conducting cyanogen chloride into alcohol ; and by 

 boiling urea for a long time with the alcohols. The 

 methyl ether (urethylan) and the ethyl ether (urethan) are 

 crystalline compounds ; easily soluble in water, alcohol, 

 and ether; volatile without decomposition. The former 

 fuses at 52-55, the latter at 100. Alkalies decom 

 pose them, forming carbonic anhydride, ammonia, and 

 the respective alcohols. 



Ammonium carbamate, CO j j^g 4 (so-called an 



hydrous ammonium carbonate), is formed by bringing 

 ammonia and carbonic anhydride together, best in the 

 presence of absolute alcohol. White, loose powder, 

 subliming at 60; or thin laminge. With water, it 

 rapidly forms ammonium carbonate. 



Sulphocarbamic acid, CS j 2 The ammonium 



salt ig formed by the action of alcoholic ammonia on 

 carbon bisulphide. It crystallizes in long, pale-yellow 



