CYANOGEN COMPOUNDS. 209 



many organic compounds (sugar, fat) with dilute nitric 

 acid, or by their explosion with saltpetre ; by heating 

 ammonium formate and oxalate or oxamide. 



Preparation. By heating mercury cyanide. A por- 

 tion of the cyanogen remains behind in the reaction as 

 a black, amorphous substance, paracyanogen, which has 

 the same percentages of its constituents as cyanogen, 

 but a higher molecular weight, and is transformed 

 into the latter at a very high temperature. 



Properties. Colorless gas, of a peculiar pungent 

 odor ; density, 1.801. Easily condensable by pressure 

 (4 atmos. at 17) and cooling (to 25); more strongly 

 cooled it becomes solid. Water absorbs four and a half 

 times its volume, alcohol twenty-three times. The 

 aqueous, as well as the alcoholic, solution decomposes 

 when kept, a brown body (azulmic acid) being thrown 

 down and hydrocyanic acid, ammonium oxalate and 

 carbonate, urea, etc., being formed; if a very small 

 quantity of aldehyde be present, oxamide is almost the 

 exclusive product. 



Cyanhydric Add, Prussic Acid. 

 CSTH. 



Formation and preparation. By the passage of elec- 

 trical sparks through a mixture of acetylene and nitro- 

 gen ; by the action of nitric acid on a great many 

 organic bodies. Most particularly prepared by the 

 distillation of 10 parts of potassium ferrocyanide with 

 a mixture of 7 parts of sulphuric acid and 14 parts of 

 water. The vapors are passed through an (J -shaped 

 tube filled with pieces of calcium chloride and stand- 

 ing in water at 30, for the purpose of drying, and 

 then in a vessel surrounded by ice. For the prepara- 

 tion of the aqueous acid, the vapors are conducted 

 directly into cold water. A very dilute solution is 

 obtained by distilling with water parts of plants con- 

 taining amygdalin. (See Glucosides, Amygdalin.) 



Properties. Clear liquid, of a peculiar narcotic odor, 

 like that of bitter almonds ; 0.7, specific gravity; boil- 

 ing point, 27, Congeals in a crystalline form at 15. 



