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