To state precisely the other relations, we must
admit, in addition, the experimental laws discovered by Pfeffer. But
without any hypothesis it becomes possible to demonstrate the laws of
Raoult on the lowering of the vapour-tension and of the freezing point
of solutions, and also the ratio which connects the heat of fusion
with this decrease.
These considerable results can evidently be invoked as _a posteriori_
proofs of the exactitude of the experimental laws of osmosis. They are
not, however, the only ones that Professor Van t' Hoff has obtained by
the same method. This illustrious scholar was thus able to find anew
Guldberg and Waage's law on chemical equilibrium at a constant
temperature, and to show how the position of the equilibrium changes
when the temperature happens to change.
If now we state, in conformity with the laws of Pfeffer, that the
product of the osmotic pressure by the volume of the solution is equal
to the absolute temperature multiplied by a coefficient, and then look
for the numerical figure of this latter in a solution of sugar, for
instance, we find that this value is the same as that of the analogous
coefficient of the characteristic equation of a perfect gas.
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