NATURE 
225 

THURSDAY, APRIL 29, 1915. 

THE VALUE OF THE RARER 
ELEMENTS. 
The Rare Earths: their Occurrence, Chemistry, 
and Technology. By S. I. Levy. Pp. xiv+ 
345. (London: Edward Arnold, 1915.) Price 
tos. 6d. net. 
HE rapidly-growing importance of the rarer 
elements in both theoretical and technical 
directions makes the above volume a welcome 
addition to English chemical literature. Except 
for Browning’s “Rarer Elements,” there is little 
of importance to turn to for information since the 
well-known “Terres rares”’ of P. Truchot, pub- 
lished in 1898. The valuable researches of Urbain 
have removed much of the obscurity that at one 
time surrounded many members of the yttra 
group, and has demonstrated the complexity of 
several that had been thought to be elementary, 
and quite recently an exhaustive study of the very 
rare earth scandia by Sir William Crookes has 
directed attention to this somewhat neglected 
branch of science. 
The title of the present work is rather mislead- 
ing, for the author deals not only with the 
rare earths proper, bodies that have always 
been a perplexity to both the chemist and the 
theorist, to the former on account of the extreme 
difficulty that attends their separation and isola- 
tion (they have a provoking habit of often turn- 
ing out to be complex even after their isolation) 
and to the latter on account of the hopelessness of 
finding a rational place for them in any of the 
periodic classifications that have appeared since 
the original work of Newlands and Mendeleeff. 
The author also discusses the elements zirconium, 
thorium, uranium, titanium, the incandescent 
mantle industry, and the manufacture of artificial 
silk! These latter are of great interest and im- 
portance, but one would scarcely expect to find 
them in a book under the title of “The Rare 
Earths.” 
The book opens with an interesting and su~- 
gestive introduction by Sir William Crookes, 
whose work on rare earths is well known, his 
numerous researches in this field extending over | 
refer | 
chiefly to the closely allied elements of the cerium | 
and yttrium groups, and with his characteristic | 
the last thirty-five years. His remarks 
forethought he states his conviction that by follow- 
ing the study of these bodies to their utmost 
limits “we may arrive at the explanation of what 
the chemical elements really are, and how they 
originated, and discover the reasons for their pro- 
perties and mutual reactions.” 
‘ The work is divided into three parts: The 
NO. 2374, VOL. 95] 

occurrence of the rare earths; the chemistry of 
the elements; and the technology of the elements. 
Each section is treated in detail, and contains a 
large amount of information, showing that the 
author has a thoroughly practical knowledge of 
his subject. 
To have at hand in one volume such a store of 
mineralogical, chemical, and technical detail is in 
itself a great boon, and the work is likely to 
become a standard of reference. 
In the chapter which deals with the 
minerals a somewhat novel classification is adopted 
“for the sake of convenience,” and an alphabeti- 
cal list is given of those minerals which contain 
the yttrium and cerium groups as well as titanium, 
zirconium, thorium, scandium, ete. ; the list is said 
to include all but a few unimportant members of 
this class; of these the larger number, printed in 
heavy type, are fully discussed in a later section. 
No mention is made of carnotite, the hydrated 
vanadate of uranium and potassium that has 
recently come into prominence as a source of 
radium, nor of the brown wiikite that occurs with 
the black variety in Finland. As a whole, how- 
ever, the list is a valuable one; it gives the name, 
composition, specific gravity, hardness, etc., of 
some 150 minerals that could otherwise only be 
found by lengthy search in recent mineralogical 
literature. 
The next section, occupying some sixty pages, 
discusses the minerals in detail, and contains an 
account of the interesting mineral thorianite, from 
Ceylon, containing 55—79 per cent. thoria and 
a considerable amount of helium from which 
radio-thorium has been prepared by Hahn; also 
the recently-discovered mineral thortveitite con- 
taining 37 per cent. of scandia. 
Prominence is given to the thorium and cerium 
minerals on account of their bearing upon the 
mantle industry; in this connection the chapters 
on the monazite sands is of great practical value, 
although carrying as little as 2 per cent. of mon- 
azite, the Brazilian deposits are of enormous 
extent and have become the chief source of the 
thoria that is needed for the mantle industry. 
Besides the Brazilian deposits, monazite occurs 
in quantity in Canada, India, South Africa, and in 
North Carolina, where in 1906 the material was 
successfully worked by the British Monazite Com- 
pany, representing the South Metropolitan Gas 
Company, of London. At this juncture, however, 
the price of thorium nitrate was suddenly lowered 
50 per cent. by the German syndicate which 
largely controlled the Brazilian output ; this caused 
the British company to cease operations, which 
have not been resumed. The American company 
working upon the same material shared a like 
K 
rare 
