NATURE 
DHURSDAY, “APRIL 4, 
1907. 
CHEMICAL CRYSTALLOGRAPHY. 
By P. Groth. 
(Leipzig:  W. 
20 marks, 
Erster 
Engelmann, 
Chemische Krystallographie. 
Teil. Pp. viii+626. 
1906.) Price 
HE appearance of the first volume of this monu- 
mental work by Prof. P. von Groth marks an 
epoch in the history of crystallography. Ever since it 
was known that the famous editor of the Zeitschrift 
fiir Krystallographie had such a work in progress, 
expectancy has been of the keenest in the mineralo- 
gical and crystallographical world. That the book 
would be worthy of the man was felt to be assured, 
and the event has fully justified such confidence. 
It is to be published in four volumes, and if the other 
three are equal to the first now before us, the whole 
will form a compendium of crystallographic lknow- 
ledge which for completeness, detail, and accuracy 
will stand unique. The work will include practically 
the whole of our crystallographic knowledge concern 
ing every crystallised substance yet described. 
There can be no doubt that Prof. von Groth is 
particularly marked out by circumstances for the com- 
pilation of such a magnum opus. For not only has 
he edited the Zeitschrift fiir Krystallographie since 
its inception by him thirty years ago, but he has ex- 
hibited from time to time, especially by the rapid 
succession of new editions of his standard text-book, 
“Physikalische Krystallographie,’? and his smaller 
but not less interesting “ Einleitung in der chemische 
Krystallographie,’’ a remarkable gift of assimilating, 
weighing, collating, and presenting in readable and 
indeed highly interesting form the chief advances in 
crystallography as they occur. His most careful per- 
sonal editorship of every paper of importance which 
is published in the Zeitschrift has rendered him 
familiar with these advances in all their details. More- 
over, his reputation as a teacher has made his labora- 
tory at Munich the resort of as earnest and enthusi- 
astic a class of students as is to be found anywhere. 
Hence this book will be received by all those interested 
in crystallography with a quite unusually warm wel- 
come, deeply tinged with reverence, partly on account 
of the excellence of the material which the book itself 
contains, but in eyen greater measure because 6f the 
respect with which every word uttered by the great 
master and universally acknowledged doyen of his 
subject is received. 
In Britain the book will meet with an exceptionally 
cordial reception from the small band of our native 
crystallographers, who have ever been treated by Prof. 
von Groth with particular kindliness, and have re- 
ceived from him the strongest encouragement, and 
never more so than at times when it has unfortunately 
been only too evident that the study of crystals was 
not appreciated in this country. The writer of this 
review can never forget the more than kind encourage- 
ment extended to him by Prof. von Groth during the 
earlier stages of the organised series of researches 
which the writer inaugurated in the year 1891 on 
the alkali sulphates and selenates and their double 
NOWIG 5.35 VOL 5 
salts, and which had for their first object the intro- 
duction of greater accuracy crystallographic 
methods. Prof. von Groth has frequently expressed 
the wish that the country of Miller, the father of 
modern crystallography, should take a much greater 
part in the advance of crystallography than she was 
doing some fifteen years ago. Now, however, at last 
the small band of British workers, partly from the 
stimulating influence of such encouragement, 
been able to make some impression, and not only 
mineralogists, who have alone in the past appreciated 
erystallography at its true value, but chemists, to 
whom its intrinsic value is immeasurable, as well as 
metallurgists and physicists, are awakening to the fact 
that the study of crystals is the study of solid matter 
in its highest, most perfectly organised form, and 
that it is likely to lead to the most important funda- 
mental truths. Already the researches just alluded 
to have afforded a final and irrefragable proof of the 
accuracy of Hatiy’s original conception that to every 
definite chemical substance there appertains a dis- 
tinct and characteristic crystalline form, and have 
reconciled this with Mitscherlich’s discoveries in 
isomorphism by revealing an exquisitely beautiful 
relationship, connecting very small angular differences 
which are found to occur between the crystals of the 
various members of isomorphous series with the 
atomic weight of the interchangeable elements com- 
posing them. This generalisation not only defines 
the real meaning, extent, and scope of Mitscherlich’s 
law, but also proves that the supposed exceptions are 
not such, and, therefore, the absolute truth of the rule 
that difference of chemical composition does in all 
cases involve difference of crystalline form. 
That the subject to the advance of which Prof. von 
Groth has devoted himself is indeed of the intrinsic 
importance which the writer has recently claimed for 
it, in a couple of articles in the engineering supple- 
ment of the Times, is strikingly demonstrated by the 
fact that the very groundwork of chemistry, the law of 
into 
has 
valency, has been shown in a remarkable paper 
by Prof. Pope and Mr. Barlow, read _ recently 
to a crowded audience at the Chemical Society, 
to be clearly connected with, if not dependent upon, 
the internal structure of crystals. This most interest- 
ing theory carries the conception of ‘‘ topic axes,” 
which express the relative structural dimensions of 
the crystals of isomorphous series, and which were 
introduced simultaneously by Dr. (now Prof.) Muth- 
mann, one of Prof. von Groth’s pupils and assistants, 
and the writer in the year 1894, a step further so as 
to include no longer merely the members of iso- 
morphous series, but also substances of the most 
diverse characters; and whatever may be the fate of 
this theory, it can no longer be doubted that crystallo- 
graphy must play a much more important réle among 
the subjects of science in the future than it has played 
in the past. 
The present juncture, therefore, is a most opportune 
one for the appearance of Prof. von Groth’s great 
book. It will be invaluable to all crystallographical 
investigators, and particularly so as an excellent biblio- 
graphy of all the important investigations up to date 
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