VI. On the thermal effects of compressing fluids

Abstract

Professor William Thomson has published a theoretical investigation of the subject of the present paper, in which he arrives at the formula θ = T ep /JK, where θ is the increase of temperature, T the temperature from absolute zero, e the expansibility by heat, p the pressure in pounds on the square foot, J the mechanical equivalent of the thermal unit in foot-pounds, and K the capacity for heat in pounds of water, of a cubic foot of the fluid employed. He has also given a Table of theoretical results for the compression of water and mercury. The investigation being established on the basis of well-ascertained principles and facts, the correctness of the Table could not be reasonably doubted. Nevertheless, believing that an experimental inquiry would be interesting if not important, I have ventured to offer the following to the notice of the Royal Society. The only previous experiments on the subject of which I am aware are those of M. Regnault. To his memoir on the Compressibility of Liquids, he appends a note on the heat disengaged by the compression of water. The method employed by this celebrated physicist, though less delicate, is similar to that which I have adopted. One set of the junctions of a thermo-electric pile was placed in a copper vessel filled with water, to which a pressure of ten atmospheres could be instantaneously communicated by means of a reservoir of compressed air. The 1/64th of a degree Centigrade could be detected by his thermo-multiplier. Nevertheless the conclusion arrived at was the negative one, that “the heat disengaged by a sudden pressure of ten atmospheres on water is unable to raise its temperature 1/50th of a degree Centigrade.”