avoided, and those parts alone are entered upon which are more
immediately necessary for the electro metallurgist to know and practice
for himself. This will account for the long description of the
cyanuret of potassium, while the preparation of the equally important
and even more used acids, the sulphuric, muriatic, etc., commonly found
in commerce, are altogether neglected.

"In using solutions of cyanide of potassium, the workman should not
immerse his arms into them, otherwise it occasionally happens that the
solution produces very troublesome eruptions over the skin."

HYPOSULPHITE OF SODA.

Hyposulphite of Soda.--This salt forms one of the important chemicals
for the Daguerreotype operator. Its application to this art is of an
interesting nature. It is used to dissolve the sensitive salt of
silver which remains unchanged during the exposure in the camera. It
has the property of readily dissolving the chloride, bromide and iodide
of silver. It should be pure and free from sulphuret of sodium; should
this last be present, it will cause brown spots of sulphurated silver
upon the Daguerreotype impression. This annoyance is a great source of
complaint from many operators, and ever will be, so long as it is
prepared by men who have no reputation to lose, and whose eyes are
blinded by the "Almighty Dollar."

A good article may be prepared as follows:

"Mix one pound of finely pulverized carbonate of soda with ten ounces
of flowers of sulphur, and heat the mixture slowly in a porcelain dish
till the sulphur melts. Stir the fused mass, so as to expose all its
parts freely to the atmosphere, whereby it passes from the state of a
sulphuret, by the absorption of atmospheric oxygen, into that of a
sulphite, with the phenomenon of very slight incandescence. Dissolve
in water, filter the solution, and boil it immediately along with
flowers of sulphur. The filtered concentrated saline liquid will
afford, on cooling, a large quantity of pure and beautiful crystals of
hyposulphite of soda."

Hyposulphite of Gold.--This compound salt is by a few considered
preferable to the chloride of gold, but our experience has induced us
to use the latter, believing we are enabled to produce a more brilliant
and warm-toned impression with it. When the hyposulphite of gold is
used in gilding, it requires less heat and a longer application, as
there is some danger of producing a glossy scum over some parts of the
surface of the