50

PROOFS OF THE LAWS OF CHEMICAL AFFINITY.

its particles is sufficient to prevent combination. But if themercury be heated to a certain degree, the force which kept itsparticles united will become annihilated, and it then combineswith the oxigen which is present.

Again, if the oxid of mercury thus formed be exposed to ahigher degree of temperature, the union is demolished, and thequicksilver re-appears in its metallic state.

Hence it is obvious that the action of caloric favors the unionof the oxigen and mercury, in consequence of the diminutionof the mutual affinity of the parts ; but at length, by augmentingthis difference, it again breaks the union, or renders the com-bination impossible.

That increased temperature augments the power of chemicalunion, the solutions of salt and water afford instances of.

A larger quantity of salt is soluble in a given quantity of wa-ter at a high, than at a low temperature, and this larger quantityof salt is again separated by cooling.

Law IV ....Chemical affinity is accompanied ly a change of tem-perature at the instant of its action.

The truth of this principle will be perceived by applyingexperiment to theory.

PROOFS OF LAW IV.

Experiment I.

Production of heat, ly the comlination of dense acids, alcalis,&c. with water.

We have mentioned already, (page 19) that when equal partsof concentrated sulphuric acid and ardent spirit are mingled to-