Cobaltous cyanide, Co(CN)2.3H20, is obtained when the carbonate is dissolved in hydrocyanic acid or when the acetate is precipitated by potassium cyanide.
It dissolves readily in water and the aqueous solution decomposes on standing; a dark-brown flocculent precipitate of azulmic acid, C 4 H 5 N 5 0, separating whilst ammonium oxalate, urea and hydrocyanic acid are found in the solution.
In many respects it resembles chlorine in its chemical behaviour, a circumstance noted by Gay-Lussac; it combines directly with hydrogen (at 50o° to 550° C.) to form hydrocyanic acid, and with chlorine, bromine, iodine and sulphur, to form cyanogen chloride, &c.; it also combines directly with zinc, cadmium and iron to form cyanides of these metals.
It shows characteristic ketone reactions, yielding a bisulphite compound and combining with hydrocyanic acid to form the nitrile of a-oxyisosuccinic acid.
Ustilago, and filling a greenhouse with hydrocyanic acid gas when young insects are commencing their ravages, e.g.
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