NALTURE 
1913. 
THURSDAY, DECEMBER 11, 
THE NEW PHYSICAL CHEMISTRY. 
Physikalische Chemie der homogenen und hetero- 
genen Gasreaktionen. By Dr, Karl Jellinek. 
Pp. xiv+844.. (Leipzig: S. Hirzel, 1913.) 
Price 30 marks. 
HIS stout volume witnesses in a remarkable 
manner to certain recent developments in 
physical chemistry—developments which bid fair 
to mark the opening of a period of fundamental 
and fruitful research, comparable in importance 
only with the years following the enunciation of 
the laws of solution and of electrolytic dissocia- 
tion. We refer, of course, to the third principle 
of thermodynamics due to Nernst, and to the 
theory of energy quanta, first deduced by Planck 
as an integral part of his radiation theory, and 
then later applied with great success by Einstein, 
Nernst, and Lindemann to the development of a 
theory of specific heats. The Nernst principle and 
the Planck theory are closely connected by the 
Boltzmann conception of entropy as a statistical 
and probability magnitude, and the changes which 
their introduction has already brought about in 
physical chemistry can be well appreciated by 
comparing Haber’s “Thermodynamik technischer 
Gasreaktionen” (published in 1905) with the 
present. book, which has been essentially written 
from the point of view of these new theories. The 
possibility of the prediction of the course and 
extent of a chemical reaction from purely thermal 
data, combined with a knowledge of certain 
physical constants, is now well within reach. 
Dr. Jellinek has not himself been directly con- 
cerned in any of the advances with which he chiefly 
deals. He is, however, favourably known both 
as a former pupil of Nernst’s, and as the author 
of some recently published elaborate and excellent 
physico-chemical investigations on hyposulphites. 
And although this volume contains no original 
work, it nevertheless deserves much praise as a 
very good exposition of the subject with which 
it deals. 
We have, at the outset, a discussion of the first 
and second laws of thermodynamics. Gaseous 
equilibria are then carefully treated, using rever- 
sible cycles, as well as entropy and the thermo- 
dynamic potential functions. The Nernst theorem 
is introduced in connection with the indeterminate 
constants occurring in the integrated form of the 
reaction isochore equation, and also, again, in 
connection with the entropy conception. A con- 
sideration of entropy and the second law from the 
statistical point of view follows. Then comes a 
detailed treatment of the theory of radiation, cul- 
NO. 2302, VOL. 92] 
419 
minating in a discussion of Planck’s formula, and 
of the properties of his oscillators and resonators. 
The next very interesting section contains much 
material previously unavailable in book form. It 
expounds a theory of specific heats founded on the 
assumption that molecules can be regarded as 
oscillating systems of definite frequencies, similar 
in properties to Planck’s oscillators, and that their 
energy content can only change by means of 
definite energy quanta or units. The methods 
(compressibility, melting point, abnormal dis- 
persion, selective emission, absorption and reflec- 
tion, photo-electric effect) by which these frequen- 
cies can be determined are reviewed, and the ex- 
cellent agreement between specific heats calculated 
on this basis and the experimental values shown. 
Other applications of the theory of quanta are 
considered (e.g., that by Haber to the heat effect 
of a chemical reaction), and the section closes with 
an excellent discussion—in a sense the keystone 
of the whole book—of the close connection be- 
tween the Nernst theorem and the theory of 
quanta. The name of Sackur is here prominent. 
The author then deals with the experimental 
side of the foregoing subjects. The technique of 
radiation measurements (more particularly in the 
infra-red region) is described, and we are given 
reviews of the methods used for specific heat deter- 
minations (several of them, e.g., the beautiful 
explosion method of Pier, developed in Nernst’s 
laboratory) and for the investigation of gaseous 
equilibria. The section dealing with the kinetics 
of the subject is short, and, with the exception 
of the reaction-velocity theories of Kriiger and of 
Trautz, contains little new. Finally come two 
brief but interesting sections dealing with the 
electrochemistry and photochemistry of gas reac- 
tions, in which the views and researches of 
Kriiger, Haber, Warburg, Einstein, and others 
find a place. 
The book is written with great enthusiasm, and 
the author is obviously well acquainted with the 
literature of his subject. Everything is admirably 
knit together and co-ordinated, and the latest 
publications are noted and given their place in the 
general scheme. The only criticism we feel in- 
clined to make concerns, not the manner in which 
the author has done his work, but the advisability 
of doing it at all in the form he has chosen. His 
\oiume contains material for at least four or five 
books. Two of these have already been written 
by Planck and one by Haber, whilst his most 
interesting chapters deal with a subject at present 
in a state of very rapid development—a subject, 
moreover, on which we may perhaps shortly 
expect an authoritative pronouncement from 
Nernst himself. The author has further, from 
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