Page:Scientific Memoirs, Vol. 1 (1837).djvu/365

Rh and the dilatation continued. A fresh quantity of liquid will then pass into the gaseous state, and a part of the sensible caloric becoming latent, the temperature of the mixture will diminish as well as Fig. 2

the pressure. Suppose the dilatation to be continued until the temperature diminishing gradually becomes equal to the temperature $$t$$ of the body $$B$$; let $$A\; F$$ be the volume and $$F\; G$$ the pressure corresponding to it. The law of the variation of the pressure will be given by a curve $$E\; G$$, which will pass through the points $$E$$ and $$G$$.

During this first part of the operation which we are describing, a quantity of action will be developed represented by the surface of the rectangle $$B\; C\; E\; D$$, and that of the mixtilinear trapezium $$E\; G\; F\; D$$.

We will now bring forward the body $$B$$, put it in contact with the mixture of liquid and vapour, and successively reduce its volume; a part of the vapour will pass into the liquid state, and as the latent heat disengaged in its condensation will be absorbed by the body $$B$$, the temperature will remain constant and equal to $$t$$. We shall thus continue to reduce the volume until all the heat furnished by the body $$A$$ in the first part of the operation has been conveyed to the body $$B$$.

Let $$A\; H$$ then be the volume occupied by the mixture of vapour and liquid; the corresponding pressure will be $$K\; H$$ equal to $$G\; F$$: the temperature remaining equal to $$t$$, during the reduction of the volume from $$A\; F$$ to $$A\; H$$, the law of the pressure between these two limits will be represented by the line $$K\; G$$ parallel to the axis of the abscisses.

Arrived at this point, the mixture of vapour and liquid upon which we are operating, which occupies the volume $$A\; H$$ under a pressure $$K H$$,