Licence: Public Domain Mark
Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![■^^^ PEOTOXIDE OP NICKEL. lOg. ammonia, considerably promotes the precipitation. Sulphide of nickel dissolves scarcely at all in acetic acid, with great difficulty in hydro- chloric acid. Sulphide of nickel precipitated boiling is almost insoluble in dilute hydi-ochloric acid, but dissolves readily when warmed with Hitric acid or nitro-hydrochloric acid. 6. Potassa and soda give a light green precipitate of hydrate of protoxide of nickel, NiO,HO [NiH.pj, which is insoluble in excess ot the precipitants, and not altered by exposui-e to the air, or by boiling (even on aclding iodine or alcohol). Carbonate of ammonia dissolves this precipitate, when collected and washed, to a gi-eenLsh-blue liquid, from which potassa or soda reprecipitates the nickel as an apple-ffreen hydrate of the protoxide. 7. Ammonia added in small quantity produces a trifling gi-eenish turbidity; a larger quantity of the reagent redissolves this precipitate readily to a blue solution containing a compound of protoxide of nickel and ammonia. Potassa and soda added to this solution precipitate hydrate of protoxide of nickel. Solutions containing salts of ammonia or free acid are not rendered turbid by ammonia. 8. If potassa or soda is added to a solution of a nickel salt and then bromine water or a solution of cMoride of soda (not iodine, distinction from cobalt) in sufficient quantity, and the mixture is heated' the whole of the nickel is thrown down as black hydrated peroxide •of nickel, wMch on adding cyanide of potassium dissolves with formation of potassium nickel cyanide. It is also reduced by a solution of ammonia and chloride of ammonium, and dissolves as ammonio-nickel oxide. The black precipitate must be filtered off from the solution, before heating it with these reagents. Dissolution takes place some- what slowly in the cold, rapidly on heating. Isr.B. The presence of non-volatile organic acids, and of sugar, prevents or impedes the precipitation of the nickel as protoxide or peroxide. 9. Ferrocyanide of potassium precipitates greenish-white ferro- cyanide of nickel, Ni^Cfy [Ni,Fe(CN)J, which is insoluble in hydro- chloric acid. 10. Perricyanide of potassium precipitates yellowish-brown ferricyanide of nickel, NigCfdy [NijFe.lCN),,], which is insoluble in hydrochloric acid. In presence of chloride of ammonium and am- monia, precipitation does not take place until the solution is boiled. 1.1. Cyanide of potassium produces a yellowish-green precipitate of cyanide of nickel, NiCy [Ni(CNy, which redissolves readily in excess of the precipitant as the double cyanide of nickel and potassium, ]SriCy,KCy [Ni(CN)2,2KCN]; the solution is brownish-yellow, and does not darken on exposure to the air. If sulphuric acid or hydrochloric acid is added to this solution, the cyanide of potassium is decomposed, and the cyanide of nickel reprecipitated; from very dilute solutions, the cyanide of nickel separates only after some time. It is very sparingly soluble in an excess of the precipitating acids in the cold, but more readily on boiling. If the solution of the double cyanide is rendered alkaline by solution of soda, being also kept so by a further addition of soda if necessary, and chlorine gas is passed into it without warming, or if bromine is added, the whole of the nickel gradually separates as black hydrate of sesquioxide. 12. On adding to solutions which are not too dilute, and which have](https://iiif.wellcomecollection.org/image/b21966953_0148.jp2/full/800%2C/0/default.jpg)
