220 Prof, Berzelim on [M A rch^ 



Hydrocyanic acid 11 



Hydrocyanate of protoxide of iron 38 



Potash 39 



Water 12 



- Thomson, who adopted Porrett's idea of the value of the fer- 

 ruginous hydrocyanic acid, examined the composition of hydro- 

 cyanate of potasn, and obtained from it the following results : 



• Acid{ir-:;:;;;J3:0*| ..45-90* 



Potash 41-64 



Water 13-00 



Dr. Thomsom states that during the decomposition of this salt 

 by -another acid, a portion of the hydrocyanate of iron is volati- 

 lized with such rapidity that when he poured nitric acid on the 

 pulverized hydrocyanate, the acid in the flask from which he 

 poured it was coloured blue by the volaiilized prussiate of iron. 

 Dr. Thomson endeavoured to analyze the acid, by burning the 

 salt with base of potash in the oxide of copper in a tube of the 

 same metal. Five grains of the crystallized salt gave 5-205 cubic 

 inches of carbonic acid gas, and 2-42 cubic inches of azote, with 

 2-2 grs. of water, 0-65 gr. of which were derived from the water 

 of crystallization of the salt. This experiment gave 2^- volumes 

 of carbonic acid gas for one volume of azote, exclusive of the 

 carbonic acid retained \)y the alkali, of which no account was 

 taken, nor, as far as appears, any deduction made, for the atmo- 

 spheric acid contained in the apparatus at the beginning of the 

 experiment. 



Dr. Thomson concludes from it, that the acid of these salts 

 contains, besides the iron, the same elements, and in the same 

 proportion as the hydrocyanic acid, because he supposes that 

 one fourth of the volume of carbonic acid gas, that he found in 

 excess, might be an error of observation, and that the quantity 

 of water, which is four times greater than the quantity admitted 

 by this supposition, was derived from the corks with which the 

 opening of the copper tube was closed, so that its hygrometrical 

 water might have mixed with the products of the analysis. 

 However when Thomson made his calculations from the results, 

 and distilled the carbon and hydrogen, which did not coincide 

 with the theory, the weight of the iron did not accord with the 

 chemical proportions. *' This," he says, " is the first compound 

 which I have met with that does not seem reconcileable to the 

 atomic theory. 1 invite chemists to the further investigation of 

 it. There are no facts so hkely to lead to the improvement of 

 the science of chemistry as those which contradict our received 



•*■■,■ 



* So in th« French. 



