CHAPTER 12 EQUILIBRIUM CONDITIONS IN MULTICOMPONENT SYSTEMS
12.4 COLLIGATIVEPROPERTIES OF ADILUTESOLUTION 382
BIOGRAPHICAL SKETCH
Jacobus Henricus van’t Hoff (1852–1911)van’t Hoff was a Dutch chemist who gained
fame from epoch-making publications in sev-
eral fields of theoretical chemistry. He was an
introvert who valued nature, philosophy, po-
etry, and the power of imagination.a
van’t Hoff was born in Rotterdam, the son
of a physician, and studied at Delft, Leyden,
Bonn, and Paris before obtaining his doctor’s
degree at Utrecht in 1874. For 18 years he was
Professor of Chemistry, Mineralogy, and Geol-
ogy at the University of Amsterdam. In 1896,
mainly to escape burdensome lecture duties,
he accepted an appointment as Professor of
Physical Chemistry at the University of Berlin,
where he remained for the rest of his life.
In the same year he received his doctor’s de-
gree, he published the first explanation of opti-
cal activity based on the stereoisomerism of an
asymmetric carbon atom. Similar ideas were
published independently two months later by
the French chemist Joseph Le Bel.
In 1884 he entered the field of physical
chemistry with his bookEtudes de Dynamique ́
Chimique, a systematic study of theories of re-
action kinetics and chemical equilibrium. The
book introduced, in the form of Eq.12.1.12,
his expression for the temperature dependence
of an equilibrium constant.
van’t Hoff next used thermodynamic cycles
to reason that solutions of equal osmotic pres-
sure should have the same values of freezing-
point depression and of vapor-pressure lower-
ing. Then, from Raoult’s extensive measure-
ments of these values, he found that the os-motic pressure of a dilute solution is described
byDicBRT(Eq.12.4.25withreplaced
byi). The Swedish chemist Svante Arrhenius
later interpretedias the number of particles
per solute formula unit, helping to validate his
theory of ionic dissociation of electrolytes.
In a celebrated 1887 summary of his theory
of osmotic pressure, van’t Hoff wrote:b
... the relation found permits of an important ex-
tension of the law of Avogadro, which now finds
application also to all [nonelectrolyte] solutions,
if only osmotic pressure is considered instead of
elastic pressure. At equal osmotic pressure and
equal temperature, equal volumes of the most
widely different solutions contain an equal num-
ber of molecules, and, indeed, the same number
which, at the same pressure and temperature, is
contained in an equal volume of a gas.... the
existence of the so-called normal molecular low-
ering of the freezing-point and diminution of the
vapor-pressure were not discovered until Raoult
employed the organic compounds. These sub-
stances, almost without exception, behave nor-
mally. It may, then, have appeared daring to give
Avogadro’s law for solutions such a prominent
place, and I should not have done so had not Ar-
rhenius pointed out to me, by letter, the probabil-
ity that salts and analogous substances, when in
solution, break down into ions.
In 1901 van’t Hoff was awarded the first
Nobel Prize in Chemistry “in recognition of
the extraordinary services he has rendered by
the discovery of the laws of chemical dynam-
ics and osmotic pressure in solutions.”
van’t Hoff was married with two daughters
and two sons. He died of tuberculosis at age
fifty-eight. In a memorial article, Frederick
Donnancwrote:d
The present writer is one of those whose priv-
ilege it is to have worked under van’t Hoff.
... Every day endeared van’t Hoff to the small
band of workers in his laboratory. His joy in his
work, the simple and unaffected friendliness of
his nature, and the marvellous power of his mind
affected us most deeply. All who worked with
van’t Hoff quickly learned to love and respect
him, and we were no exception to the rule.
aRef. [ 123 ]. bRef. [ 162 ]. cDonnan was an Irish physical chemist after whom the Donnan membrane
equilibrium and Donnan potential (Sec.12.7.3) are named. dRef. [ 46 ].