NATURE 
291 
THURSDAY, MAY 1914. 
21, 
CHEMISTRY: ANCIENT AND MODERN. 
Some Fundamental Problems in Chemistry—Old 
and New. By Prof. E. A. Letts. Pp. xii+ 
235 + plates. (London: Constable and Co., 
Lfd:) “Baee 756d. net. 
HOSE chemists whose memories can carry 
them back for a period of about half 
a century will have experienced several phases in 
the development of the science which, at their 
respective periods, were regarded as marking a 
transition from an older to a newer chemistry. 
The writer of this notice began his reading when 
was HO and so forth. Then came the 
“new notation” resulting from the proper recog- 
nition of Avogadro’s law, the doubling of certain 
atomic weights, and the reconstruction of our 
formule. This was the ‘new chemistry” of that 
period. Next arose the more complete elabora- 
tion of the conception of constitution or structure 
based on valency, due to Frankland and Kekule, 
and we had a yet newer chemistry—a develop- 
ment which was so extraordinarily prolific in the 
way of results that chemists were inclined to hug 
themselves into the belief that they had come to 
close quarters with the inner mechanism of mole- 
cular structure, and the very weaknesses of the 
theory, which had shown signs of breaking down 
in certain directions, afterwards became corner- 
stones of strength .in the light of the brilliant 
hypothesis of van’t Hoff and Le Bel, which in- 
augurated the then new science of stereochem- 
istry. Moreover, about the same period when 
structural chemistry was undergoing these develop- 
water 
ments, attention was being more systematically 
concentrated upon the relationships of the chem- 
ical elements among themselves, these studies 
culminating that periodic classification 
sociated with the names of Newlands, Mendeléeff, 
and Lothar Meyer. From that great generalisa- 
tion arose a still newer chemistry which system- 
atised the whole treatment of the science, both 
theoretically and practically, and dominates our 
present Another “new” chemistry 
must be added to this record—the application of 
purely physical methods to the study of chemical 
phenomena in the foundation of 
‘physical chemistry’ as a distinct subject. 
All these phases are familiar to the modern 
student of the history of the science, and they 
fall into the category of what the author of the 
present work would term the. older chemistry. 
Dr. Letts does not, however, deal with all: these 
developmental epochs; the older chemistry- 
distinguished from ancient chemistry—is limited 
NO. 2325, VOL. 93| 
in as- 
teaching. 
resulting 
as 
| 
by him to the discussion of the methods and re- 
sults of atomic weight determinations by the older 
as well as by the most recent workers in this field, 
and to a very full consideration of the periodic 
law and its consequences. The reader will find no 
reference to those fundamental problems relating 
to chemical and dynamics which the 
physical chemists have formulated as the results 
of their familiar terms as mass 
action, Osmotic pressure, electrolytic or ionic dis- 
sociation, stereochemistry, etc., do not appear in 
the index. This criticism amounts simply to the 
statement that the author professes to deal only 
with certain of the fundamental problems, and 
within the limits thus assigned, he handles his 
subject in a very lucid and suggestive way. Fis 
treatment of the periodic law, for example, to 
which two chapters are devoted, goes far beyond 
the arid description found in the ordinary text- 
books and may be commended as worthy of most 
serious consideration by all students. Workers 
on the look-out for new elements may take courage 
from Dr. 
cording to which there remain either thirty-eight 
twenty-five gaps the periodic table now 
waiting to be filled up (p.,60). Another valuable 
feature of this section is the new “atomic volume ” 
curve, constructed by the author from the most 
recent available data, and, for the first time, com- 
prising the group of “inert” elements. As_ will 
be seen on reference to the original work, this 
curve differs in some important particulars from 
that first given to our science by Lothar Meyer in 
1870, and opens up some interesting suggestions 
with respect to missing elements. 
Although the older chemistry is treated of in 
the present work within the limits specified, the 
reader will gather from the subsequent chapters 
that these older workers—and happily for our 
science that generation has not yet become ex- 
tinct—have passed on to the newer school a very 
goodly heritage. By the “newer chemistry ” Dr. 
Letts understands that great body of observed 
facts and theoretical deductions which have been 
accumulated since the study of the action of the 
electric discharge upon highly attenuated, gaseous 
matter was seriously taken in hand by physicists 
and chemists, and since the discovery of radio- 
activity and the radio-active elements. How much 
of this newer knowledge will be passed on as 
canonical to future generations it would be very 
rash to predict. It is, however, certain that 
chemistry, by the discovery of unexpected pheno- 
mena, and by the utilisation of novel methods of 
attacking the ultimate components of matter, has 
now entered upon a new era in its history—a 
state of affairs which both students and teachers, 
N 
statics 
studies; such 
Letts’s suggested classifications, ac- 
or in 
