The bicyanide of mercury is a compound of mercury and cyanogen. It is
usually sold in the form of white, opaque, heavy, crystals, which are
rhomboidal prisms. It has a disagreeable, corrosive, metallic taste. It
is easily known from every other substance by the effects of heat. If a
small quantity of it, previously well dried, be introduced into a glass
phial to which a small tube is fitted by means of a cork, on the
application of heat the salt becomes black; mercury is sublimed, and
condenses in globules on the upper part of the phial; and a gas escapes,
which has the odour of prussic acid, and burns with a beautiful rose-red
flame.