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

drawn 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

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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 $KH$,