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204 MECHANICAL DENTISTRY AND METALLURGY.

Formulas for Gold Plate used for Clasps, Wire, Back-
ings, etc.— (jold used in the formation of clasps, backings,
etc., is improved for these purposes by the addition of suffi-
cient platinum to render it firmer and more elastic than
the alloys ordinarily employed in the formation of plate as
a base. The advantages of this elastic property, in its
application to the purposes under consideration, are, that
clasps formed from such alloys will adapt themselves more
accurately to the teeth, as, when partially spread apart on
being forced over the crowns, they wnll spring together
again and accurately embrace the more contracted portions.
In the form of stays or backings, additional strength being
imparted, a less amount of substance will be required; the
elasticity of these supports, also, will not only lessen the
chances of accident to the teeth themselves in mastication
and otherwise, but preserve their proper position when
temporarily disturl)ed by any of the forces applied to them.

Fonniila A^i. i. Formula No. 2.
20 dwts. pure gold, 20 dwts. gold coin,
2 dwts. fine copper, 8 grs. fine copper,
I dwt. fine silver, 10 grs. silver,
I dwt. platinum. 20 grs. platinum.

The alloy derived from either of these formulas will be
twenty carats fine.
Gold Solders.—Solders are a class of alloys by means
of which the several pieces of the same or of different
metals are united to each other. They should be more
fusible than the metals to be united, and should consist of
such components as possess a strong affinity for the sub-
stances to be joined.
When zinc or brass enters into the composition of solders,
these metals shotild be added after the other constituents
are entirely melted, and just before the molten mass is cool
enough t(j commence to solidify. The alloy should then be