1821.] the Composition of Prussiates. 435 



According to experiment. According to calculation.* 



Iron 8-81 8-68 67843 



Lead 65-91 66-18 5178-00 



Carbon 11-05 ll-55\ lofiT.^o 



Azote 12-84 13-59/ J^t)/ ^Z 



98-61 100-00 7823-95 



Thus the result of analysis approaches that by calculation as 

 near as can be expected in an operation of so complicated a 

 nature. 



If we apply this to the salt with base of potash, we get the 

 following result : the relation of the volume of the carbonic acid 

 gas, found by experiment, was to that of the azote as 3 ; 2, and 

 the weight of the carbonic acid gas obtained from 7'72 grs. of 

 salt was 4-13 grs. : if we add one-third the quantity necessary 

 to make the volume of carbonic acid twice that of the azote, the 

 weight of the carbonic acid will be rather more than 5'5 grains, 

 or 11 for 100 grains of the salt; but if the ferruginous prussiate 

 of potash be composed of one atom of cyanuret of iron and two 

 atoms of cyanuret of potassium, 100 grs. will give 11-10 grs. of 

 carbonic acid gas, a difference within the limits of inaccurate 

 observation. 



The composition of this prussiate, in the state of crystals, cal- 

 culated after the formula, ^Fe Cy^ + 2 K Cy^ + 6 Aq, gives 

 per cent. 



Iron 12-85 = protoxide of iron, 16*54 



Potassium 37*11 = potash 44-68 



Cyanogen 37-22 



Water 12*82 



I think it useless to give the result of the calculation of the 

 two other salts analyzed. They accord Ovith the following for- 

 mula : Fe Cy^ + 2 Ba Cy^ + 12 Aq ; and Fe Cy"- + 2 Ca Cy^ 

 + 24 Aq. But we must remember that, although in a state of 

 efflorescence, these two salts retain an atom of water, for some 

 reason not very easily explained. 



These experiments prove that the salts called prussiates, or 

 ferruginous hydrocyanates, are in fact cyanurets, composed of 

 one atom of cyanuret of iron and two atoms of cyanuret of the 

 other metal. 



What is the nature of these compounds when they contain 

 water? It is more difficult to answer this question than at first 

 it seems to be. In the ferruginous prussiates of potash and 

 lead, there is exactly the quantity of water necessary to trans- 

 form them into hydrocyanates, whence they may be considered 



* According to the formula, Fe Cy* + 2 Pb Cy». 



§ I use the sign Cy for cyanogen instead of N C*, to avoid compl 



2 e2 



lex numbers. 



