A NEW CLASS OF SALTS. 
517 
Name of salt. 
Number of analyses 
furnishing the mean. 
Quantity of iron. 
Mean. 
Quantity of carbon. 
Mean. 
Atomic relation of 
iron to carbon. 
Nitroprusside of sodium 
9 
19-54 
20-03 
28 
: 28-7 
Nitroprusside of potassium 
5 
19-05 
19-63 
28 
: 28-8 
Nitroprusside of ammonium 
3 
22-08 
22-69 
28 
: 28-7 
Nitroprusside of silver 
4 
13-03 
13-29 
28 
: 28-5 
Nitroprusside of copper 
4 
20-43 
21-25 
28 
: 29-0 
Nitroprusside of iron 
3 
19-09 
19-96 
28 
: 29-2 
Nitroprusside of zinc 
1 
20-07 
20-53 
28 
: 28-6 
Nitroprusside of calcium 
1 
21-09 
21-47 
28 
: 28-5 
Nitroprusside of barium 
2 
14-10 
14-98 
28 
: 29-7 
Nitroprussic acid 
3 
23-80 
24-80 
28 
: 29-1 
Mean of the whole 
35 
192-30 
198-63 
28 
: 28-9 
Now the proportion of 1 equiv. of iron to 5 equivs. of carbon would require the 
proportion 28 ; 30. This difference is too great-4o be due to any errors of observa- 
tion, especially when it is remembered that these, in the case of a body containing 
much nitrogen, tend to increase and not to diminish the apparent quantity of carbon. 
The actual proportion found, 28 : 28’9, indicates, in equivalents, 5 equivs. iron to 
24 equivs. carbon ; this proportion would require 28 : 28’8 ; the slight excess found is 
in the direction of the known errors of observation. 
These considerations forced the adoption of the complex formula given above. It 
will also be seen, from an examination of the analytical details, that the quantity of 
nitrogen corresponds to 6 equivs. for every 10 equivs. of carbon, or 15 equivs. for the 
24 equivs. of carbon required by the formula. As 12 of these are in the state of 
cyanogen, as shown both by the transformation of the nitroprussides 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 countenance 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 
nitrons 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 
proportion as in the hypothetical radical ferrocyanogen ; 5 equivs. ferrocyanogen have 
the formula Fcg Cyis; 1 equiv. of nitro-ferrocyanogen has the formula Fcs Cyi 2 3NO. 
The nitroprussides are therefore supposed to contain a ferrocyanogen in 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 ferrocyanides or ferridcyanides. Liebig supposes these 
two latter 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. 
3 X 
MDCCCXLIX. 
