XXIV. On the nitroprussides, a new class of salts

Abstract

1. In an inquiry into the constitution of the prussides, I found it necessary to examine into the somewhat anomalous action of nitric acid on the yellow prusside of potassium. This examination has led to the discovery of a singular class of compounds, which form the subject of the present memoir. The previous knowledge on the action of nitric acid on the prussides may be summed up very briefly. Thomson examined the gases produced during the action, and recognized them to be nitrogen, cyanogen, nitric oxide, and carbonic acid, while the residue was believed to consist of pernitrate of iron and nitrate of potash. Dobereiner remarked that previous to the complete decomposition of the prussides, a strong coffee-coloured liquid was produced, which, after neutralization, precipitated protosalts of iron of a dark blue colour. Gmelin, to whom chemistry was already indebted for important discoveries in the prussides, observed that the coffee-coloured liquid noticed by Dobereiner was rendered of a magnificent purple or blue colour on the addition of an alkaline sulphide. The same fact was noted by Mr. Mercer of Oakenshaw, without his being aware that it had already been remarked by Gmelin. Campbell, in repeating Gmelin’s experiment, threw out the intelligent suggestion that the purple colour might be due to the production of a sulphuret of nitrogen, which Gregory had already remarked produced an amethystine colour when mixed with an alcoholic solution of potash. Smee, in an examination of the action of nitric acid on the prussides, observes that ferridcyanide is produced, nitric oxide being evolved.