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519

The great solubility of the phosphate of lime, in even
the weakest of the acids, is very extraordinary : phosphate
of lime mechanically suspended in water, is speedily and
completely dissolved, by passing a copious stream of car-
bonic acid gas through it.
Sulphuric acid, of the specific gravity 1.83, appears at
first to have no action : in the course of an hour small bub-
bles are perceived, the roots became blackened, and in twelve
hours the enamelled part bursts, cracks, and separates, ac-
companied with an evident formation of selenite by the ac-
tion of the acid on the lime which enters into the composi-
tion of the teeth.
Nitric and muriatic acid, of the specific gravity 1.12, act
instantly on the tooth, accompanied with an evolution of
a quantity of small air bubbles from the whole of the sur-
face. About eight times their weight of these acids, are suffi-
cient for the solution of the solidifying principles of the teeth.
The mass left undissolved has nearly the original form of the
tooth, is flexible, semi-transparent, and easily divided with the
nail.
The dilute acetous acid (distilled vinegar) has a very tri-
fling action, but when concentrated, acts both on the phos-
phate and carbonate of lime.
Boiling nitric acid, acts strongly on the teeth, with the
evolution of carbonic acid, and a considerable quantity of
azotic gas. The gelatine and solid substance are dissolved
as the surfaces present themselves, but the operation being
stopped at any part of the process, the residuum is firm and
hard, but reduced in size, proportioned to the time the tooth
has been acted upon.

* Fox, Natural History of the Teeth, pages 94 to 96.