A text-book of physical chemistry / by R.A. Lehfeldt.

  • Robert Alfred Lehfeldt
Date:
[pref. 1899]
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of physical chemistry / by R.A. Lehfeldt. Source: Wellcome Collection.

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

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    density, elasticity, electric conductivity—depend on the mechanical treatment that the solid has undergone. So that even if the preliminary difficulty of obtaining a chemically pure material be overcome—which is not easy, because frequently a small trace of impurity produces a dispro- portionately large effect on the j)hysical properties —the material will show varying properties according as it is cast, rolled, wire-drawn, annealed, &c., i. e. according to the previous history of the specimen used; whereas fluids, if of identical chemical composition, are always of identical physical properties, or to use a mathematical phrase, the various physical constants of a fluid are functions of the state of the fluid at the moment, while in solids that is not in general the case. Hence very few data of value have been arrived at with regard to the physical properties of solids. § 1. Density of Fluids. The most important constant to measure in a fluid is its density (or specific volume) under varying conditions of temperature and pressure. [If J? be the pressure on the fluid, T its absolute temperature, V its specific volume, there exists a relation f{p, V, T) = 0, which is called the characteristic equation of the fluid. The various measurements described below give the means of determining the form and constants of this equation, over various portions of the entire range of temperature and pressure. The simplest instance of a characteristic equation is that of a perfect gas, — RT Another of importance is van der Waals' equation, to whicli we shall have to return in detail below.]
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