The father of
physical chemistry
Chemistry in Britain, 2003, 39, (5) 32-34 Reproduced with permission of the Royal Society of Chemistry. |
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'Picture
to yourselves a friendly enthusiastic man, with penetrating eyes, fresh
colour, and reddish hair, moustache and beard, going the round of the
research laboratories every day. If you had a difficulty, Ostwald had a
solution to offer. If you had no difficulties, you probably got some new
ideas. If you had any views on music, painting or philosophy, the Master was
full of attention and would discuss them with you'
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Wilhelm Ostwald, best known for
his work on catalysis and chemical affinity, was born 150 years ago this
year.
Michael Sutton describes the life
of this energetic man.
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In the
course of a strenuous career, Wilhelm Ostwald published 45 books, over 500
articles, and about 5000 reviews. He also edited six scholarly journals, and
organised the reprinting of a lengthy series of historic chemical papers. By
his 50th birthday he had supervised 147 graduate students, 34 of whom became
professors. He was honoured by over 60 universities and learned societies,
and in 1909 won the Nobel prize for chemistry. Ostwald took an active
interest in philosophical, social and political issues, and devoted much time
and effort to the cause of world peace and international understanding.
Always interested in the arts, he played the viola in a string quartet when
young, and in retirement became an enthusiastic landscape painter. For 52
years he was happily married to Helene von Reyher, with whom he raised two
daughters and three sons. It seems entirely appropriate that Ostwald devoted
much of his life to the study of energy. Ostwald's
family belonged to the German community in Riga - now the capital of Latvia,
but then part of the Russian Empire. Gottfried Wilhelm Ostwald was a master
cooper (barrel maker), and his wife Elisabeth (née Leuckel), the daughter of
a master baker. Their second child, born on 2 September 1853, was christened
Friedrich Wilhelm, and educated at the Riga Gymnasium (high school). His
father hoped the boy would become an engineer, but in 1872 Wilhelm entered
the University of Dorpat to study chemistry. (Dorpat was also under Russian
rule then - renamed Tartu, it is now in Estonia.) At first, Ostwald neglected
the official curriculum in favour of art, music, philosophy and the convivial
student life. However, some last-minute cramming got him through the
theoretical chemistry course, and in 1875 he was admitted to Karl Schmidt's
laboratory. Ostwald soon progressed from routine exercises to original
investigations, gaining his doctorate in 1878. Part-time work as a laboratory
assistant allowed him to continue research at Dorpat until he became
professor of chemistry at Riga Polytechnic in 1881. Ostwald
remained at Riga until called to a chair at Leipzig in 1887. In that year he
founded the Zeitschrift für physikalische Chemie, which soon established him
as an influential figure in the scientific world. But by then, much of his important
research had already been done, far away from the major centres of European
science, using inexpensive home-made apparatus. Ostwald believed it was this
isolation from the academic mainstream that inclined him towards the
unfashionable field of physical chemistry. While most of his contemporaries
were busy discovering new substances and reactions, he sought to understand
the forces that drove reactions and bound molecules together. For years, he
measured the changes in physical parameters that accompanied chemical
processes. One early project was an attempt to estimate the relative
affinities of various substances, using pairs of compounds with one shared
component. Suppose,
for example, that A and A* are two acids, and B is a base with which they
both combine. Then, if a solution of AB is mixed with a solution of A*, some
quantity of A is displaced by A*, yielding a mixture of AB and A*B (with
proportional quantities of both free acids). Ostwald used delicate volumetric
measurements to investigate reactions of this type. Suppose a litre of
aqueous solution containing a gram-molecule (mole) of A is added to a litre
of a solution of B, also containing one gram-molecule. The final volume will
differ slightly from 2l, by an amount we can call v. Again, if 1l of a
similar solution of A* is added to a litre of a similar solution of B, the
volume of this mixture will differ from 2l by a different amount, v*. And if
1l of an AB solution is mixed with 1l of an equivalent solution of A*, then
the volume - call it v# - by which the mixture differs from 2l will indicate
how much AB has been converted to A*B. From these volume changes, Ostwald
could compare the strengths of the attractive forces between A and B, and
between A* and B. In
the late 1870s Ostwald had considerable success in comparing affinities by
measuring the changes in volume (and other physical parameters like
refractive index) that accompanied chemical reactions. His results generally
agreed with the law of mass action, which relates the quantities of the
products of a chemical reaction to the concentrations of the reactants. Two
Norwegians, Peter Guldberg and Cato Waage, had stated the law and explored
its implications in a series of papers beginning in 1864. However, their work
remained virtually unnoticed until Ostwald publicised and extended it in the
early 1880s. Meanwhile,
the Dutch physical chemist Jacobus van't Hoff (1852-1911) showed how the
experimentally derived mass action law could be deduced directly from
thermodynamic principles. He found that the molecules of dissolved substances
behaved, in some respects, like molecules in the gaseous state. In
particular, the universal gas equation, PV = RT often applied accurately to
solutions (P representing osmotic pressure, and V the volume containing one
gram-molecule of solute). Ostwald was one of the first to recognise the
importance of this breakthrough. Unfortunately, there was a difficulty. The
gas constant, R, sometimes had to be multiplied by an arbitrary figure to
make the equation fit the observations. The significance of this multiplier -
'van't Hoff's i factor' - became clear when the Swedish physical chemist
Svante Arrhenius developed his theory of ionic dissociation. Ostwald
saw the significance of this insight when it emerged - somewhat obscurely -
in Arrhenius' 1884 doctoral thesis on the conductivity of electrolytes. The
two became friends and collaborators, and a more accessible version of
Arrhenius' theory appeared in Ostwald's Zeitschrift für physikalische Chemie
in 1887. They showed that van't Hoff's i factor was not arbitrary - it
represented the proportion of dissolved molecules that separated into
oppositely charged ions. The osmotic pressure exerted by a solution was
recognised as being proportional to the number of dissolved particles, rather
than to the number of dissolved molecules. Thus far, Ostwald's principal role
had been to clarify, coordinate and extend the ideas of van't Hoff and
Arrhenius. However, in 1887 he made an original contribution - Ostwald's
dilution law, usually expressed as follows: a2/(1-a)v
= k (where
a represents the degree of ionic dissociation, v the volume of solution in
litres containing one gram-molecule, and k is a constant.) Ostwald soon
realised that k was also the equilibrium constant for many dissociation
reactions of the form: AB Ostwald
and his collaborators showed that hundreds of water-soluble acids and bases
obeyed the dilution law, while their behaviour in solutions conformed to the
general ionic theory. They hailed this as the start of a new era in
chemistry, but others were sceptical. Critics pointed out that only weak
electrolytes obeyed the rules discovered by Ostwald, Arrhenius and van't Hoff
- indeed, it was not until the 1920s that Pieter Debye, Erich Hückel and Lars
Onsager developed a satisfactory theory of strong electrolytes, which
explained their anomalous behaviour in terms of inter-ionic attraction. Besides
studying chemical reactions that had already reached equilibrium, Ostwald,
together with his research students, also measured the rates at which
reactions proceeded towards the equilibrium state. These kinetic investigations
demonstrated that while catalysts could alter the rates of reactions, they
did not change the proportions of the final products. This discovery had
profound implications for industry and for chemical theory. It was cited as
the principal reason for Ostwald's Nobel award - the presenter declaring:
'Catalysis, which formerly appeared to be a hidden secret, has thus become
... accessible to exact scientific study'. Ostwald
was also interested in measuring the energy absorbed or released in chemical
reactions. He quickly recognised that the thermodynamic studies of the
American physicist Willard Gibbs were useful in this context. Gibbs' heavily
mathematical papers were hard reading for European chemists, but Ostwald
strove to make them more accessible, while always giving the originator full
credit. By
the 1890s Ostwald was deeply absorbed in the theoretical and philosophical
problems surrounding the concept of energy. He became convinced that matter
was merely 'a mirage which the mind creates to comprehend the workings of
energy'. Though accepting that atoms and molecules were convenient symbols
for statistical regularities in our observations, he insisted that the basic
truths of science should be expressed in terms of energetics, without
reference to these hypothetical particles. In 1909, after much controversy,
Ostwald was finally persuaded by new physical evidence (including Jean
Perrin's studies of Brownian motion) to accept the reality of atoms.
Nevertheless, his stubborn scepticism had prompted a reassessment of the
experimental grounds for belief in entities that were not directly
observable. After
retiring from academic life in 1906, Ostwald undertook a wide variety of
philanthropic activities. Some produced valuable results, others failed utterly,
but all were grounded in a commitment to scientific progress and humanitarian
values. His attempt to promote Ido (an improved version of Esperanto) as an
international language attracted few converts. His involvement with the
utopian biologist-philosopher Ernst Haeckel and his 'Monist League'
accomplished little, while causing Ostwald considerable financial loss. His
efforts for Der Brücke (The Bridge) - an organisation seeking to stimulate
and coordinate intellectual and cultural activity across national boundaries
- were similarly unfruitful. In the more limited field of scientific
collaboration, he played an important part in founding an international
Association of Chemical Societies. However, the outbreak of war in 1914
marked the collapse of Ostwald's hopes for wider international cooperation. As
a patriot, but not a militarist, Ostwald hoped to see an honourable peace
negotiated as quickly as possible. Consequently, he was criticised by fellow
Germans for his lack of zeal, and by friends abroad for his unwillingness to
condemn the war outright. In this depressing atmosphere, Ostwald turned away
from public affairs, and developed one last research project. Always
fascinated by the borderlands between science and art, he made a systematic
analysis of colour phenomena and our perception of them. His aim was to
supplement our subjective and qualitative classification of colours with a
quantitative and objective one, and to establish principles of colour
harmony, analogous to the harmonic rules of music. He
achieved considerable success in this endeavour, and his colour
classification system was widely adopted. In his final years, Ostwald moved
on to more general speculations on the philosophy of aesthetics, and the
scientific principles underlying our awareness of harmony and proportion. He
died on 4 April 1932. Shortly afterwards, Wilder Bancroft, a former pupil,
summed up the impact of his life in these words: 'He was loved and followed
by more people than any other chemist of our time'. |
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Further reading W. Bancroft, J. Chem. Ed., 1933, 10, 539. W. H. Brock, The Fontana history of chemistry, p377.
London: Fontana, 1992. F. G. Donnan, J. Chem. Soc., 1933, 316. E. N. Hiebert and H.-G. Köber, 'Wilhelm Ostwald' in
C. C. Gillispie (ed), Dictionary of scientific biography, Vol XV
(supplement), p316. New York: Charles Scribner's Sons, 1978. H. Hildebrand, Nobel award presentation speech 1909,
www.nobel.se/chemistry/laureates/1909/press.html
N. R. Holt, Brit. J. Hist. Sci., 1977, X, 146. K. J. Laidler, The world of physical chemistry, p
28, p209. Oxford: OUP, 1993. W. Ostwald, Nobel lecture 1909, www.nobel.se/chemistry/laureates/1909/ostwald-lecture.html
J. R. Partington, A history of chemistry, Vol IV,
p595. London: Macmillan, 1964 |
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If you are interested in further information
on Wilhelm Ostwald’s biography, don’t be shy to ask: |
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Wilhelm-
Ostwald- Archiv und Gedenkstätte Grimmaer
Strasse 25 D-04668 Grossbothen |
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tel.: +49 (0)
34384 / 71429 fax.: +49 (0)
34384 / 72691 |
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for email, please type without spaces: o s t w a l d e n e r g i e @ a o l . c
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