arthy matter--chiefly phosphate of lime, and the remainder
is gelatine. When bones are digested in muriatic acid they become
transparent and flexible like leather, the earthy matter is
dissolved, and after the acid is all carefully washed away, pieces
of glue of the same shape as the bones remain, which are soluble in
hot water and adapted to all the purposes of ordinary glue, without
further preparation.

Another important application of sulphuric acid may be adduced;
namely, to the refining of silver and the separation of gold, which
is always present in some proportion in native silver. Silver, as it
is usually obtained from mines in Europe, contains in 16 ounces, 6
to 8 ounces of copper. When used by the silversmith, or in coining,
16 ounces must contain in Germany 13 ounces of silver, in England
about 14 1/2. But this alloy is always made artificially by mixing
pure silver with the due proportion of the copper; and for this
purpose the silver must be obtained pure by the refiner. This he
formerly effected by amalgamation, or by roasting it with lead; and
the cost of this process was about 2l. for every hundred-weight of
silver. In the silver so prepared, about 1/1200 to 1/2000th part of
gold remained; to effect the separation of this by nitrio-hydrochloric
acid was more expensive than the value of the gold; it was therefore
left in utensils, or circulated in coin, valueless. The copper, too,
of the native silver was no use whatever. But the 1/1000th part of
gold, being about one and a half per cent. of the value of the silver,
now covers the cost of refining, and affords an adequate profit to
the refiner; so that he effects the separation of the copper, and
returns to his employer the whole amount of the pure silver, as well
as the copper, without demanding any payment: he is amply remunerated
by that minute portion of gold. The new process of refining is a most
beautiful chemical operation: the granulated metal is boiled in
concentrated sulphuric acid, which dissolves both the silver and the
copper, leaving the gold nearly pure, in the form of a black powder.
The solution is then placed in a leaden vessel containing metallic
copper; this is gradually dissolved, and the silver precipitated in
a pure metallic state. The sulphate of copper thus formed is also a
valuable product, being employed in the manufacture of green and
blue pigments.

Other immediate results of the economical production of sulphuric
acid, ar