A Manual of the Chemistry of the Carbon Compounds

THE CARBON COMPOUNDS. 57
violet lustre. By decomposing this salt with the sulphates of the
othei metals the whole series of platinocyanides can be obtained,
amongst which the magnesium salt Pt(CN)4 Mg + 7H2O is one of
the most beautiful; it forms fine large square prisms, of a deep red
colour by transmitted light; but when viewed by reflected light the
aides of the prisms exhibit a brilliant beetle-green, and their extremities
a deep blue or purple colour. On adding sulphuric acid to
a solution of the platinum salt, hydrogen platinocyanide Pt(CN)4H2 is
obtained, which crystallizes from a concentrated solution in long
prisms, having a splendid vermilion colour, accompanied by a blue
iridescence.
COMPOUNDS OF CYANOGEN WITH THE HALOID ELEMENTS.
Cyanogen GlUoride CNC1.—To piepaie this compound chlorine is
passed in the absence of light into a mixture of one part of anhydrous
hydrocyanic acid, and five parts of water, the vessel being
surrounded by a freezing mixture. Cyanogen chloride separates out
as a mobile colourless liquid, heavier than water. It possesses a very
irritating odour, attacking the eyes and producing a copious flow of
tears; it boils at 15 - 5°, and solidifies at-5°. lie pure compound
may be kept for yearg without undergoing any change, but in the
impure state it very soon changes into the polymeric cyan/uric
cUoride.
Cyanogen Bromide CNBr is a very volatile solid body, subliming
in needles, soon changing however into cubes; it smells like the
chloride.
Cyanogen Iodide CNI is easily obtained by heating an intimate
mixture of mercuric cyanide and iodine. It forms fine colourless
needles, and has a pungent smell. It is frequently found in large
quantities in commercial iodine.
Cyaniiric Chloride (C^Ng^Clj.—This compound is formed as already
mentioned by the polymerisation of cyanogen chloride, and is also
obtained by acting in annlight with chlorine on anhydrous hydrocyanic
acid or its solution iu ether. It crystallizes in shining needles or
scales, which melt at 145° and boil at 190°. Its odour is, especially
on heating, pungent and producing a flow of tears.
CYANIC ACID AND CYANATES.
Metallic cyanides readily absorb oxygen, cyanates being formed.
To prepare polassitm cyatwie KOC'N, prussiate of potash and potassium
carbonate are fused together, and red lead is gradually added. The
melt is exhausted with hot spirits of wine; frorn this solution the
salt crystallizes on cooling, in needles or plates. It is readily soluble