NEP. — BIVALENT CARBON. 187 



N:C 

 I 



N:C, 



and not, as has so long been supposed, derivatives of cyanogen, 



I 



Tlie analogy between fulminic acid and prussic acid is further 

 shown by the isolation of a double salt, sodic ferrofulminate, 



Na4Fe(ON.C)6 



corresponding completely with sodic ferrocyanide, 



Na4Fe(N:C)6. 



Carstanjen and Ehrenberg have already drawn attention to the very 

 peculiar behavior of sodic fulminate towards iron salts, and shown 

 that solutions result in which the presence of iron can no longer be 

 detected,* 



On adding to an aqueous solution of sodic fulminate containing 

 some sodic hydrate, and obtained as stated above from mercuric 

 fulminate (32 grams), a solution of ferrous sulphate (one molecule 

 to six molecules sodic fulminate), a yellowish solution is obtained, 

 in which the presence of iron cannot be detected either by means 

 of sodic hydrate or of ammonium sulphide. The filtered solution 

 is allowed to evaporate spontaneously ui flat dishes in the air, and 

 after some time beautiful yellow needles, often over an inch in length, 

 separate out. It is easily possible to obtaui 11 grams of this sub- 

 stance in a perfectly pure state from the above amount of mercury 

 fulminate taken. The crystals are filtered off, washed with a small 

 amount of cold water, and then dried between filter paper ; they do 

 not contain a trace of sodium sulphate. 



On further evaporation of the mother liquors, more of the salt sepa- 

 rates out, but mixed with Glauber's salt. The sodic ferrofulminate 

 thus obtained is freely soluble in cold water, and gives with ferric 

 chloride an intense purple-red coloration, which is incredibly delicate. 

 The pure substance is, however, unstable in aqueous solutions or in a 

 moist condition,- and soon gets colored purplish red ; the presence of 

 sodic hydrate increases its stability, and for this reason it is well to 

 recrystallize in the presence of a small amount of sodic hydrate. The 



* Journ. f prakt. Chem., [2.], XXV. 246, 247. 



