The latent heat of pressure variation of liquid ammonia

Abstract

When a fluid undergoes a change of pressure, there occurs a transtormation of energy into heat or vice versa, which results in a change of temperature of the substance unless a like amount of heat is abstracted or added. This change expressed as the heat so transformed per imit change of pressure will be called "latent heat of pressure variation." For most liquids under usual conditions of temperature and pressure this quantity, which depends on the thermal expansivity, is small compared with the other quantities of heat which are usually observed, but for liquid ammonia in the range —40 to +40° C and corresponding saturated vapor pressures it is sufficiently large to be taken into account in calorimetric determinations of specific heat; and, in consequence, the measurements here described were made as a supj^lement to a series of such determinations in order to correlate measurements of specific heat of liquid ammonia ^ made at constant pressure with others made under saturation conditions.