446 Professor Berzelius on [June, 



I prepared it in the following manner: I took some cyanuret 

 of iron and lead which had been well washed but not dried, and 

 I decomposed it under water by a current of sulphuretted hydro- 

 gen gas, until the sulphuretted hydroojen was in excess. I 

 immediately filtered it, and evaporated it in vacuo in the usual 

 manner. But as sulphuretted hydrogen spoils the air-pump, I 

 afterwards took the precaution to decompose the sulphuretted 

 hydrogen by the addition of a small quantity of cyanuret of iron 

 and lead. The filtered fluid remained limpid and colourless in 

 vacuo, and it eventually leaves a milk-white opaque substance, 

 -which has no appearance of crystallization. This white matter 

 has the following properties : it dissolves in water, to which it 

 imparts an acid and agreeable flavour, but which is rather 

 astringent. In contact with the air it deposits prussian blue, 

 and assumes a greenish colour. It is inodorous, unless it has 

 begun to decompose. When boiled, the liquid gives out hydro- 

 cyanic acid, and deposits a powder which becomes blue in con- 

 tact with the air. It is necessary to boil it for some time to 

 decompose it entirely. The fluid, when half decomposed by 

 ^bulhtion, has seemed to me to possess a more astringent taste ; 

 I will not assert, whether by this operation, there is formed 

 an hydrocyanate of iron with a smaller excess of acid. If cold 

 water be saturated with dry superhydrocyanate, and the solution 

 be suffered to remain, it gives small transparent colourless crys- 

 tals which appear to contain water of crystallization, but I have 

 not been able to determine their form. The crystals are formed 

 in groupes composed of concentric rays. The rays appeared to 

 me to be quadrilateral prisms. If I were permitted to conjecture,, 

 i would say that these crystals are a hydrocyanate in which 

 water replaces the second base that existed with the protoxide of 

 iron. The white substance obtained by evaporation in vacuo does 

 not appear to contain any water, or rather appears to be the super- 

 hydrocyanate of protoxide of iron without water of crystalliza- 

 tion ; for if it be distilled in a small and proper apparatus, it 

 gives at first hydrocyanic acid ; afterwards carbonate of ammo- 

 nia and prussiate of ammonia. The production of ammonia in 

 this experiment proves that what remains after the hydrocyanic 

 acid which is first evolved is a hydrocyanate, and not a cyanuret, 

 because, in the latter case, it could only have given hydrocyanic 

 acid and azotic gas . This substance may be kept without alte- 

 ration in well-closed vessels, but in the air it gradually decom- 

 EGses, becomes at first greenish, afterwards blue, and finishes 

 y being entirely converted into prussian blue. 



V. On the Decomposition of Hydrocyanates by Exposure to a 

 High Temperature in close Vessels, 



It is evident from what I have above stated that several cya- 

 nurets when exposed to heat in closed vessels must exhibit 



