Page 160 - The Wellington photographic handbook

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The salt is too well known to need description here. It is only
used in photography in very small quantities to neutralize any
acidity in the gold chloride solution and in the hypo solution used
for self-toning paper. The ordinary household quality answers
every purpose.
Sodium Bisulphite (also called acid sulphite of soda).
This should be in the form of fine white crystals.
Sodium Bisulphite Lye.—A concentrated solution of sodium
bisulphite saturated with sulphurous acid gas. Principally manu-
factured for use in bleaching works, and employed in photography
for compounding acid fixing baths.
Sodium Carbonate (called also carbonate of soda, but must
not be confused with the bicarbonate, which is quite a different
substance. Washing soda is impure sodium carbonate).—This is
usually met with in the form of perfectly clear dry glassy crystals,
which is the form referred to in the formulae in this book. The
crystals should be kept in a well-corked bottle or they go powdery
and white, and should not then be used. The salt is readily soluble
in hot or in cold water. Its solutions will keep in good condition
for a long while, but should not be put into stoppered bottles, as
they make the stoppers stick. Another form of sodium carbonate
on the market is called " anhydrous sodium carbonate." This is a
fine, white powder. It can be substituted in any of the foregoing
formulae by multiplying the quantity of the carbonate crystals
specified by five and dividing the result by fourteen. The result
is then the corresponding quantity of the anhydrous.
Sodium Sulphide (not to be confused with sodium sulphite
or sodium sulphate).—What is known as pure crystallized sodium
sulphide is the substance referred to under this name. It is generally
to be met with in large, greenish white, wet-looking crystals, having
a most offensive smell of rotten eggs. As it rapidly absorbs moisture
from the air it should not be kept in stock for any long period.
In concentrated solution it will keep for a few months.
Sodium Sulphite (also called sulphite of soda, not to be
confused with sodium sulphide, or with sodium sulphate).—This
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