SECOND LECTURE.

Thermodynamic States of Equilibrium in Dilute

Solutions.

In the lecture of yesterday I sought to make clear the fact
that the essential, and therefore the final division of all processes
occurring in nature, is into reversible and irreversible processes,
and the characteristic difference between these two kinds of
processes, as I have further separated them, is that in irreversible
processes the entropy increases, while in all reversible processes
it remains constant. Today I am constrained to speak of some
of the consequences of this law which will illustrate its rich fruit-
fulness. They have to do with the question of the laws of ther¬
modynamic equilibrium. Since in nature the entropy can only
increase, it follows that the state of a physical configuration
which is completely isolated, and in which the entropy of
the system possesses an absolute maximum, is necessarily a
state of stable equilibrium, since for it no further change is
possible. How deeply this law underlies all physical and chem¬
ical relations has been shown by no one better and more com¬
pletely than by John Willard Gibbs, whose name, not only in
America, but in the whole world will be counted among those of
the most famous theoretical physicists of all times; to whom, to
my sorrow, it is no longer possible for me to tender personally
my respects. It would be gratuitous for me, here in the land
of his activity, to expatiate fully on the progress of his ideas,
but you will perhaps permit me to speak in the lecture of to¬
day of some of the important applications in which thermo¬
dynamic research, based on Gibbs works, can be advanced be¬
yond his results.

These applications refer to the theory of dilute solutions, and

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