it condenses into a colorless fluid, with a density 1.069. It is
obtained from decomposition of fluorspar by strong sulphuric acid.
It readily dissolves the silica in glass, and consequently cannot be
kept in a vessel of that material. It is prepared and kept in lead.
It is employed in accelerators on account of its fluorine.

One small drop on the tongue of a dog causes death.
The operator who wishes to use it should pour some
of the liquid for which he intends it into a graduate,
or other vessel, and then add the desired quantity of acid.
If by accident any of the spray should fall upon the skin,
it should at once be copiously drenched with water.

Sulphuric Acid.--There are two sorts of this acid:
one is an oily, fuming liquid; this is made in Nordhausen,
in Saxony, and is commonly called "Nordhausen sulphuric acid,"
or oil of vitriol. The other which is the kind used in
connection with the Daguerreotype, is common sulphuric acid.
It is somewhat thinner, and when undiluted is not fuming.
This acid may be obtained in a solid and dry state,
called anhydrous sulphuric acid.

The common sulphuric acid is made by burning sulphur, which forms
sulphurous acid. To convert this into sulphuric acid and gain
more oxygen, nitric acid, which is rich in that body, is added.
It forms a limpid, colorless fluid, of a specific gravity
of 1.8. It boils at 620 deg.; it freezes at 15 deg.
It is acrid and caustic, and intensely acid in all its characters,
even when largely diluted.