Page 94 - My FlipBook

90 GENERAL REMARKS ON FILLING.

feet crystallization of the gold, combine the precipi-
tate with from six to twelve times its weight of pure
mercury, let it stand a short time, subject to a gentle
heat, and then remove the mercury with dilute nitric

acid. Afterward wash the nitrate of mercury from
the gold place the latter upon a slide, and bring it up
;
to a full red heat in a muffle, and the gold is then in
a condition to be used for filling. This is about the
formula on which a patent was granted to A. J.
Watts. The preparation possesses some advantages
over gold foil : it is as readily introduced ; it is more
it has, besides the
capable of thorough consolidation ;
cohesiveness of foil, the additional property of inter-
lacing its crystals one with another, by which prop-
erty, even without cohesion, the pieces of a filling
can be firmly united ; and it takes a better hold upon

the walls of the cavity, to which it presents the
angles and ends of the crystals, so as to be more
thoroughly adapted and fastened.
Amalgam.—By this term are designated all those
preparations formed by a combination of mercury
with various other metals ; most frequently with sil-
ver and tin, but occasionally with gold, platinum,
bismuth, cadmium, zinc, and lead. The several form-
ulas for amalgam need not here be specified. The
kind most in use is prepared by melting together and
carefully mixing pure tin and silver, filing this mix-