A NEVV^ CLASS OF SALTS. 
485 
fact the formula Cy-f 2HO correctly represents the composition, and the substance 
may be supposed to be formed by the union of cyanogen in its nascent state with 
2 equivs. of water. When this white substance is treated with acids, it is converted 
into oxalic acid and ammonia. This fact, together with the analysis, proves it to be 
OxAMiDE*. Its occurrence in a process of oxidation is very surprising, and perhaps 
may throw some doubts on the theoretical composition ascribed to it, 2 CO+NH 2 . 
There is little doubt that this substance is the same as that observed by VAUQUELiN-f- 
in a watery solution of cyanogen, which however was not analysed by him. The 
description which he gives applies closely to oxamide. Wohler;]: also observed two 
substances in a watery solution of cyanogen, one of which may be this body. The 
appearance of carbonic acid is now explained, as it is obviously due to an oxidation 
of the oxalic acid produced by the transformation of the oxamide. 
Section II . — General remarhs on the Nitroprussides. 
9. The nitroprussides are salts with characters so decided, that they cannot be con- 
founded with any known series of compounds. They are generally highly coloured — 
the salts of potassium, ammonium, sodium, barium, calcium and lead being of a dark 
red or ruby colour ; they are readily soluble in water, and communicate a dark red 
colour to the solution. Alcohol does not precipitate these salts from their solutions. 
The soluble nitroprussides crystallize readily, yielding large and well-defined crystals. 
The nitroprussides of copper, zinc, iron, nickel, cobalt and silver, are either wholly or 
nearly insoluble. 
The following Table exhibits some of the characteristic reactions of a soluble nitro- 
prusside : — 
Reagents. 
Behaviour of the nitroprusside. 
Sulphides of the alkaline metals 
Magnificent transitory purple colour. 
Sulphuretted hydrogen 
Produces prussian blue, a prusside and peculiar compound. 
Neutral salts of lead 
No change. 
Basic salts of lead 
White precipitate, after a time in strong solution. 
Persalts of mercury 
No change. 
Proto- and persalts of tin 
No change. 
Salts of zinc 
Light salmon-coloured precipitate. 
Salts of copper 
Light green precipitate. 
Salts of nickel 
Dirty white precipitate. 
Salts of cobalt 
Flesh-coloured precipitate. 
Protosalts of iron 
Salmon-coloured precipitate. 
Persalts of iron 
No change. 
Caustic alkalies 
Turn the red coloured solutions of an orange colour. 
The beautiful colour immediately produced on the addition of a soluble sulphide, 
is a most marked character of the nitroprussides. This purple coloration is most in- 
* In the descriptions of oxamide, it is usual to state that all acids convert it into oxalic acid and ammonia. 
It is however very readily soluble in concentrated sulphuric acid, from which it is again precipitated unchanged 
by the addition of water. 
t Ann. de Chim. et de Phys. ix. 113; xxii. 132. 
3 R 
MDCCCXLIX. 
J PoGG. Ann. XV. 627. 
