a Neio Class of Salts. 359 ' 



As 1 2 of these are in the state of cyanogenj as shown both by 

 the transformation of the nitropriissides by alkalies and by 

 sulphides, the remaining 3 equivs. must be in the form of an 

 oxide of nitrogen. But the loss on the analyses does not 

 admit the supposition that the oxide is nitric oxide, as might 

 have been supposed, neither do the transformations counte- 

 nance this idea. The oxygen is in the proportion of 3 equivs. 

 for every 3 equivs. of nitrogen ; the nitrogen not present as 

 cyanogen must exist as nitrous oxide. This is unusual, and 

 its functions must therefore be inquired into. It will at once 

 be seen that if nitrous oxide is supposed to substitute and play 

 the part of cyanogen, the iron and the non-electro-negative 

 bodies with which it is associated are present in the same pro- 

 portion as in the hypothetical radical ferrocyanogen ; 5 equivs, 

 ferrocyanogen have the formula Fe^ Cy^^; 1 equiv. of nitro- 

 ferrocyanogen has the formula Fe^ Cy^^ 3N0. The nitro- 

 prussides are therefore supposed to contain a ferrocyanogen 

 m which 3 equivs. of cyanogen are substituted by 3 equivs. 

 of nitrous oxide. 



32. But the proportion of the electro-positive element in 

 the nitroprussides is less than that existing either in the ferro- 

 cyanides or ferridcyanides. Liebig supposes these two lattev 

 compounds to differ by containing different radicals, one being 

 twice the atomic weight of the other. It would be equally 

 instructive to suppose that they both contain the same radical, 

 but that, as in the case of the different phosphoric acids, one 

 is quadribasic, while the other is tribasic. 



Quadribasic prussides, Fe^Cy^4-4<R, formula of ferrocya- 

 nides. 



Tribasic prussides, Fe^ Cy^ + 3R, formula of ferridcyanides. 



Bibasic prussides, Fe^Cy^ + 2R, formula of undescribed 

 compounds. 



With regard to the last class, its existence must be yet con- 

 sidered hypothetical, but in searching for it, I have received 

 sufficient encouragement to enable me to hope that I shall 

 very shortly be able to establish it. Without presenting the 

 analytical evidence to this effect, it can only be adduced as a 

 probable hypothesis to explain the nitroprussides. The latter 

 class of salts may be supposed to correspond to a bibasic class 

 of prussides in which part of the cyanogen is replaced by 

 nitrous oxide. Thus5(Fe Cy^ + R) = Fe^ Cy^^ + 5R correspond 

 to 1 equiv. of a nitroprusside, Fe* Cy^^ 3NO + 5R. The great 

 approximation of the latter formula to the more simple ex- 

 pression Fe^Cy^ NO + 2R, renders it singular that the small 

 deficiency of carbon refuses to allow the formula to be thus 



