A manual on dental metallurgy / by Ernest A. Smith.

  • Smith, Ernest A. (Ernest Alfred)
Date:
1903
Catalogue details

Licence: In copyright

Credit: A manual on dental metallurgy / by Ernest A. Smith. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    209/334 (page 189)
    Platinum may also be estimated in amalgam alloys by melting the alloy in a small crucible and gradually adding mercuric chloride, by which means the tin is removed as a volatile chloride. This must be done in a draught cupboard to carry off the fumes produced, as it is dangerous to inhale them. The button of silver left behind contains the platinum (and gold if present). It is treated with nitric acid, as above described. 2. Platinum in dental alloy may be conveniently estimated by treating a weighed quantity of the alloy with nitric acid, which dissolves all the silver and part of the platinum. On introducing a sheet of zinc into the solution the silver and platinum are precipitated, and on treating this precipitate with nitric acid the silver only is dissolved. The two quantities of platinum are then put together, washed, heated to redness, and weighed. The platinum precipitate may also be dis- solved in aqua regia, the metal precipitated with ammo- nium chloride and weighed as spongy platinum as previously directed. The silver may be recovered from the solution in .the usual way by precipitation as chloride (see p: 169). Alloys.—Platinum will alloy with most of the other metals under the influence of heat, producing bodies which are usually considerably more fusible than platinum itself. Platinum and Gold.—These metals combine with the formation of alloys which are more fusible than platinum, the melting-point being lowered as the quantity of gold increases. The alloys are elastic and ductile, and their colour approaches more or less to that of gold as tlie ])rupor- tion of the latter is increased.