The laws of
cryoscopy, of tonometry, and of osmosis thus again become strict, and
no exception to them remains.
If the dissociation of salts is a reality and is complete in a dilute
solution, any of the properties of a saline solution whatever should
be represented numerically as the sum of three values, of which one
concerns the positive ion, a second the negative ion, and the third
the solvent. The properties of the solutions would then be what are
called additive properties. Numerous verifications may be attempted by
very different roads. They generally succeed very well; and whether we
measure the electric conductivity, the density, the specific heats,
the index of refraction, the power of rotatory polarization, the
colour, or the absorption spectrum, the additive property will
everywhere be found in the solution.
The hypothesis, so contested at the outset by the chemists, is,
moreover, assuring its triumph by important conquests in the domain of
chemistry itself. It permits us to give a vivid explanation of
chemical reaction, and for the old motto of the chemists, "Corpora non
agunt, nisi soluta," it substitutes a modern one, "It is especially
the ions which react.
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