Dental metallurgy; a manual for students and dentists.

  • Griffiths, A. B. (Arthur Bower), 1859-
Date:
1903
Catalogue details

Licence: In copyright

Credit: Dental metallurgy; a manual for students and dentists. Source: Wellcome Collection.

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    Specific Heat of a metal is its capacity for heat in com- parison to the unit (water). Specific heat is the quantity of heat required to raise a given weight of any metal through a certain range of temperature, as compared with the quantity required to raise the same weight of water through the same range of temperature. Thus, to raise 1 llj. of iron one degree requires of the quantity of the heat required to raise 1 lb. of water one degree; hence the specific heat of iron is OT (water =1). The specific heats of the metals are very vaiiable. Hammering, heating, etc., reduces the specific heats; and this property must be taken into consideration in the manu- facture of plates for artificial dentures. The high specific heat and the low conductivity of palladium render it suitable for plates, as these properties prevent the chill felt in the mouth with a gold plate on drinking cold liquids, and also prevent scalding with hot fluids. Conductivity for Heat.—The property of conducting heat is one of the chief characteristics of the metals, or, in the words of Berzelius: “ la propriete d’etre meilleurs con- ducteurs du calorique que les autres corps, est un des caracteres les plus saillants des nidtaux.” The metals are the best conductors of heat among solids, but their power varies considerably. Silver and copper are the best conductors, while antimony and bismuth are the worst. Conductivity for Electricity.—The metals are also good conductors of electricity, but the power of conduction varies considerably. Silver and copper are the best, and lead, anti- mony, and bismuth the worst conductors. The conductivity is reduced by a rise of temperature, but this reduction varies with each metal. Electrical conductivity is defined as the reciprocal of rc- sistance, and the name “ microhms ” has been given by Lord Kelvin to the unit of conductivity. The specific conductivity