a New Class of Salts. 207 



The carbon is to the nitrogen as 2 : 1, or in the same pro- 

 portion as cyanogen. In fact the formula Cy + 2HO cor- 

 rectly 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 am- 

 monia. 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 theo- 

 retical composition ascribed to it, 2CO + NH2. There is 

 little doubt that this substance is the same as that observed by 

 Vauquelinf 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 sub- 

 stances in a watery solution of cyanogen, one of which may 

 be this body. The appearance of carbonic acid is now ex- 

 plained, as it is obviously due to an oxidation of the oxalic 

 acid produced by the transformation of the oxamide. 



Section II. — General remarks on the Nitroprnssides. 



9. The nitroprussides are salts with characters so decided, 

 that they cannot be confounded 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 in- 

 soluble. 



The following table exhibits some of the characteristic re- 

 actions of a soluble nitroprusside : — 



Reagents. Behaviour of the nitroprusside. 



Sulphides of the alkaline metals... Magnificent transitory purple colour. 



Sulphuretted hydrogen /Produces prussian blue, a prusside and 



*^ ./ o 1^ peculiar compound. 

 Neutral salts of lead No change. 



Basic salts of lead ~. fWhite precipitate, after a time in strong 



1. solution. 

 Persalts of mercury No change. 



* 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. 



\ Ann. de Chim. et de Phys., ix. 113; xxii. 132. 



X Poggendorff 's Annalen, xv. 627. 



