The Nobel Prize in Chemistry 1932
Irving Langmuir
Presentation Speech by Professor H.G.Söderbaum, Chairman of the Nobel Committee for Chemistry of the Royal Swedish Academy of Sciences, on December 10, 1932
Your Majesty, Your Royal Highnesses, Ladies
and Gentlemen.
Superficiality is a quality which has always had a bad
reputation, not least within the field of science and among
scientific practitioners. In these circumstances it may possibly
arouse some surprise that, in awarding this year's Nobel Prize
for Chemistry, the choice of the Royal Academy of Sciences has
fallen on a work on surface chemistry. But here, as often in
other cases, it is necessary not to let words obtain too great a
power over thought. If one frees oneself of this power and
investigates the matter more closely, it will be found, on the
contrary, that in reality surface chemistry has contributed
greatly to the deepening of our knowledge of matter in its most
minute particles.
Surface chemistry as the designation of a special discipline
within physical chemistry is a comparatively new conception. The
phenomena with which it is concerned are none the less well-known
since of old.
One of these phenomena is that of adsorption. The power of
certain solid bodies to retain or, as we say, to condense gases
on their surface has long been known and made use of for all
manner of practical purposes. But it has not been known how this
adsorption really takes place - and opinions have been divided as
to what forces operate thereby. As a rule the conception will
probably have been that the gas nearest to the adsorbing solid
body, thus in the boundary surface between the solid and the
gaseous condition itself, appears in a more or less condensed
state, and that the density decreases continuously outwards in
proportion as the solid surface is left, in about the same way as
the density of the atmosphere of the earth decreases upwards in
proportion as we move away from the solid crust of the earth.
This year's Nobel Prize winner in Chemistry has advanced an
entirely confticting theory and one which at first sight seems to
be particularly bold.
According to this theory the layer of gas adsorbed is limited -
in ideal border-line cases at least - to an extremely thin film
of gas molecules extending over a single plane, thus a film whose
thickness is that of a single molecule or, in other words, is
monomolecular. And the force which retains the gas particles is
derived from the chemical field of forces of the surface atoms,
in that the atoms on the boundary surface are conceived as
partially unsaturated and, in virtue of their so-called residual
valences directed outwards, equipped with the power to bind a
corresponding number of atoms in the gaseous body. And since
these residual valences - in any case in crystalline bodies -
must be conceived to make their effects felt at fixed points and
at fixed distances from each other, it follows immediately that
the adsorbed gas particles also will lie at fixed distances from
each other and at fixed points. One can visualize it most easily
if one thinks of the adsorbing solid surface as a chess-board,
where each square can only be occupied by a single gas particle.
When all the squares are occupied adsorption ceases.
Now it may be asked: Is there any real basis for such an
assumption? Can one really adduce in proof anything which seems
so to escape direct observation? With the view of answering these
questions I will venture to borrow an example from an account
sent in to the Academy of the work which has been awarded the
prize.
Assume that hydrogen gas is exposed at very low pressure in an
electric bulb to the influence of the hot metal filament. The
hydrogen gas molecules are broken up, dissociated into atoms, and
these are strongly adsorbed by the glass surface of the wall of
the lamp, if the latter is kept well-cooled with liquid air. One
finds then that a maximum quantity of hydrogen is taken up by the
glass surface, or by a certain part of it, let us say one square
centimetre. On the other hand, the size of the hydrogen atoms is
known, and so the number of atoms which ought to find room on the
same surface unit can be calculated. It is then shown that the
quantity of hydrogen gas thus calculated is in satisfactory
agreement with that previously found. The layer of hydrogen gas
is thus, approximately at least, only of the thickness of one
layer of atoms.
Another experimenter has allowed a known surface of metallic gold
to adsorb air during the transition from a very high vacuum to
ordinary atmospheric pressure. With the help of an extremely
sensitive micro-balance he has been able to make a direct
determination of the amount of air thus retained by the gold and
found that it corresponds to a layer of oxygen and nitrogen
molecules of only the thickness of one molecule.
Quite new methods of determination, based on the use of electron
bombardments and the determinations of electron interferences,
have finally indicated that when, for example, hydrogen is
adsorbed on the surface of a nickel crystal, a regular pattern is
formed, where the distance between the atoms of hydrogen is twice
as great as the distance between the atoms of nickel. Thus, a
pretty confirmation of the conception of the adsorbing surface as
a chess-board, where the adsorbing particles are retained in
definite positions.
The work which has been awarded the prize does not, however,
comprise only investigations concerning the adsorption in the
boundary surface between gases and solid bodies, but also
investigations concerning the thin films in the boundary surface
between gases and liquids and concerning the adsorption on the
surfaces of liquids. The well-known phenomenon of the spreading
of an oil film has served as a starting-point for these
investigations and the determination of the lateral pressure with
which such a film opposes attempts to diminish its surface.
It has been found inter alia that there are such films
where the molecules can move around each other freely, something
like the molecules in a gas, but with the difference that here
they only move in two dimensions, while in an ordinary gas they
move in three. This has opened a new and important field for
investigations in chemistry: the study of the conditions of
matter in the two-dimensional world, and has in addition afforded
valuable information, not only as to the structure of molecules,
but also as to the forces working within and between them.
In the rules of the Nobel Foundation we read: "No work shall have
a prize awarded to it, unless it has been proved by the test of
experience or by the examination of experts to possess the
pre-eminent excellence that is manifestly signified by the terms
of the will."
In this respect, if at first there could have been any
uncertainty as regards the work now awarded the prize, this
uncertainty has been ever increasingly dispelled in the light of
the researches of the last few years, to be succeeded by an
increasing insight into the fact that the work breaks entirely
new ground and that considerable parts of it are of lasting
value.
This value appears in a still clearer light if we reflect that a
multitude of chemical reactions of the utmost importance both
technically and biologically, not to mention physiologically, are
precisely surface reactions and consequently cannot be fully
comprehended or mastered without an intimate knowledge of the
nature of the elementary surface processes.
Numerous scientists are at the present time working industriously
and successfully in this field of research. It would seem,
however, that greater honour is due to the first man, the
pioneer, who has broken new ground, than to the cultivators of
ground already cleared, however industrious they may be.
Influenced by these considerations the Royal Academy of Sciences
has decided to award this year's Nobel Prize for Chemistry to Dr.
Irving Langmuir of Schenectady "for his outstanding discoveries
and investigations within the field of surface chemistry".
The Royal Swedish Academy of Sciences is sure that it is acting
in accordance with the views of the scientific world in awarding
to you this year's Nobel Prize for Chemistry for your most
important discoveries and researches in the field of surface
chemistry.
In proffering to you the sincere congratulations of our Academy,
I have the honour of asking you to receive this prize from the
hands of His Majesty the King, who has been graciously pleased to
undertake to present it to you.
From Nobel Lectures, Chemistry 1922-1941, Elsevier Publishing Company, Amsterdam, 1966
Copyright © The Nobel Foundation 1932
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