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. 



{S P 2 TT 5 

 S*C 2 H 5 ( isomeric 

 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 mercaptau and 

 urea. 



Carbamic acid, CH^O 2 = CO j ^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 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 laminse. With water, it 

 rapidly forms ammonium carbonate. 



Sulphocarbamic acid, CS \ ^ The ammonium 



salt is formed by the action of alcoholic ammonia on 

 carbon bisulphide. It crystallizes in long, pale-yellow 



