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.

    49/334 (page 29)
    Expansion op Metals by Heat. (rrentes/ Jixpaiisioii. Cadmium . Lead Zinc . Aluminium Tin . Silver Copper Bismuth . 0.00306 = ^ij^ 0.00292 = 0.00291 = ^l-j 0.00231 = 0.00223 = ^hs 0-00193 = 0.00167 = -FF? 0.00162 = ^» Gold Nickel Iron (malleable) Palladium Iron (cast) Antimony Platinum 0.00145 0.00127 0.00122 0.00117 0.00107 0.00105 0.00089 _ 1 — jsr — 1 Least Expansion. The above table indicates the linear increase or coefficient of linear expansion—that is, the increase in one direction. Most substances, however, expand equally in each direction, and the cubical expansion may be taken as approximately three times the above fractions. Change of Volume on Solidification.—All metals undergo a change of volume when they pass from^ the fluid to the solid state. With the exception of bismuth, which expands, all metals contract on solidification. This change of volume is a matter of great practical importance not only in the arts but in many branches of dentistry. It is one of the most im- portant properties to be considered in the selection of a metal for the production of dies for swaging metal plates, as the successful adaptation of the plate depends to a large extent upon the die being an accurate repre- sentation of the precise form of the mouth. Owing to this general property of contraction it is impossible to obtain a metal which will give an exact reproduction of the mouth. The unavoidable shrinkage, however, is partially or wholly compensated for by the ex])ans'ion of the plaster model employed, and the yielding condi- tion of the soft tissues of the mouth. Although the