CHAPTER V.
SOLUTIONS AND ELECTROLYTIC DISSOCIATION Sec.1.

SOLUTION Vaporization and fusion are not the only means by which the physical state of a body may be changed without modifying its chemical constitution.

From the most remote periods solution has also been known and studied, but only in the last twenty years have we obtained other than empirical information regarding this phenomenon.
It is natural to employ here also the methods which have allowed us to penetrate into the knowledge of other transformations.

The problem of solution may be approached by way of thermodynamics and of the hypotheses of kinetics.
As long ago as 1858, Kirchhoff, by attributing to saline solutions-- that is to say, to mixtures of water and a non-volatile liquid like sulphuric acid--the properties of internal energy, discovered a relation between the quantity of heat given out on the addition of a certain quantity of water to a solution and the variations to which condensation and temperature subject the vapour-tension of the solution.

He calculated for this purpose the variations of energy which are produced when passing from one state to another by two different series of transformations; and, by comparing the two expressions thus obtained, he established a relation between the various elements of the phenomenon.