AND THE PARACYANIC ACID. 45 



At incipient redness, it blackens, and at a red heat bums like tinder, leaving me- 

 tallic sUver. 



6. When heated in close vessels, it gives off water, carbonate of ammonia, 

 carbonic acid, and nitrogen, and leaves a black residue, which, at a red heat, yields 

 cyanogen. The carbonic acid and nitrogen are in the ratio of 2 to 1, as they are 

 also when the salt is burned with oxide of copper or bi-chromate of potash. 



7. a. 3.33 grs. dried at 212° F. in LiEBie'stube, left of metallic silver 1.34 = 

 40.24 per cent. 



h. 7.16 grs. burned with bi-chromate of potash gave 0.96 grs. of water = 

 13.40 per cent. 



c. 9.08 grs. burned with oxide of copper gave 6.49 grs. of carbonic acid = 

 1.7945 of carbon, or 19.702 per cent. 



These give for the constitution of the salt, 



Here, as in the analysis of the uncombined acid, the carbon obtained is in 

 excess, and probably from the same cause, — the formation of oxides of nitrogen, — 

 which in burning paracyanogen and its compounds, it seems almost impossible 

 wholly to prevent. 



Paracyanate of Iron. — When a solution of sulphate of protoxide of iron is 

 poured into one of paracyanic in nitric acid, a yellow precipitate falls, not very 

 copiously, which is soluble in hot dilute nitric acid, and falls in great part on 

 cooUng. Heated in the air it becomes brown, blackens, then bums like tinder, 

 leaving metallic iron, which rapidly oxidizes. 



Pai-acyanate of Lead may be formed by mixing together a solution of nitrate 

 of lead with one of the paracyanic, evaporating to dryness, and washing the mass 

 with cold water. 



The washings of both these salts give copious precipitates with nitrate of pro- 

 toxide of mercury. 



Alkaline Paracyanates. — The affinity of this acid for the alkalies seems to be 

 singularly small. In large excess they partially decompose the metallic salts, 

 and dissolve small quantities of the uncombined acid forming yeUow solutions ; 

 but they exhibit little inclination to form neutral salts. _ Perhaps it is, that the 

 neutral paracyanates of the alkaline bases are also but sparingly soluble in pure 



