292 
NATURE 
[May 23, 1912 
chemistry, and only very occasionally touched 
upon in the later chapters of the book. Such a 
text-book had undoubted advantages from the 
point of view of the teacher ; the text-book supplied 
the dry bones of chemistry, and in a course cf 
lectures the flesh and blood could be added with- 
out any undue risk of duplicating the teaching 
derived from the book. But for the solitary 
student it was an obvious disadvantage that such 
questions as mass-action and reversible changes 
should be dealt with in an isolated chapter, and 
their application to the “daily round” of chemical 
changes forgotten or neglected. It was to remedy 
this defect that the book now under review was 
written. The author has not merely professed the 
policy of stating facts before theories, but, in wel- 
come contrast with some recent writers, has held 
to this policy, so that atomic weights are not 
introduced until chapter x., page 115. Criticism 
of the book is largely limited to points of detail. 
Thus the adoption of the old convention that one 
molecular proportion of a gas occupies ‘two 
volumes” appears to the writer to introduce un- 
necessary confusion, and seems to carry with it 
some lurking suspicion that the oxygen molecule 
O, occupies two volumes because it contains two 
atoms, although the volume occupied is precisely 
the same in the case of the monatomic molecule 
of mercury. More emphasis might have been 
placed upon the fact that molecular weights are 
now referred to O,= 32 instead of H,=2, the state- 
ment on p. 109 that “the molecular weight of a 
gas double its vapour density referred to 
hydrogen as unit” being therefore only an ap- 
proximation and not an exact definition; we have 
also not noticed on a first reading any statement 
of the fact that Avogadro’s hypothesis is itself 
only an approximation which becomes accurate 
only at zero pressure. 
In reference to the illustrations, two points have 
been noticed. The crystal drawings on p. 302 
are for the most part correct, but have been 
printed in curious positions, the upper part of the 
figure being on the right in Fig. 60, on the left 
in Fig. 65, and at the bottom of Fig. 63. In 
Fig. 24.the author has perpetuated the mistake 
(so often repeated as almost to have become a 
dogma of the chemical creed) of representing 
Dumas’s experiments on the composition of water 
as having been made with a Bunsen burner with 
U-tubes of the modern pattern some six or eight 
inches long; a reference to the original paper 
shows that these tubes were a metre in height, 
and that the beak of the massive copper oxide 
bulb was also a. metre long; on this scale the 
retort stands of the figure would be 8 ft. high, 
and the interpolated Bunsen burner about 2 ft. 
high ! 
NO. 2221, VOL. 89] 
is 
The periodic classification of the elements given 
on p. 364 shows the elements praseodymium = 
140°5 and neodymium=143'6 as members of the 
nitrogen and oxygen groups respectively. In view 
of the extraordinary similarity of these two 
elements such a separation is very undesirable, 
and there is every reason for preferring Prof. 
Armstrong’s arrangement, in which the rare earth 
elements, from lanthanum= 139 to ytterbium=173, 
form a vertical column in the boron or aluminium 
group; precedents for such an arrangement 
already exist in the clusters Fe, Co, Ni; Ru, Rh, 
ecinancda@s,. line ibite 
These criticisms deal entirely with matters of 
detail. Turning to more general considerations, 
it may be noted that the information given is. 
modern and accurate, and that reference is made 
to a considerable number of observations pub- 
lished during the year 1911, which appears upom 
the title-page. The style is clear, the book is 
attractively printed, and the author has un- 
doubtedly succeeded in his endeavour to introduce 
something of the spirit of physical chemistry into 
the routine of descriptive chemistry. 
(2) The American text-book is in striking con- 
trast to the serious work of our first author. An 
endeavour has been made 
“to bring out the humanistic side of the science, 
to use as far as possible that material which is 
laden with intense human interest because of its 
significance to the race.” 
In so far as this has led the authors to introduce 
excellent portraits of Dalton, Lavoisier, Faraday, 
and Kekulé it is to be commended, although 
Arrhenius, as shown facing p. 260, would scarcely 
be recognised by his friends. But they proceed 
to illustrate chemical energy by a picture of a 
forest being cleared by dynamite, and an obscure 
photograph of an automobile, enveloped in dust 
and steam, travelling at 80 miles an hour; rapid 
oxidation is illustrated by the burning of San 
Francisco, and slow oxidation by a picture of a 
bird nesting in a hollow tree; other illustrations. 
show a primeval forest, a coal mine, hydraulic 
gold-mining in California, and the granite rocks 
of the Sierra Nevada mountains. The book has 
evidently been written for American readers, and 
| 1s not likely to come into general use in England. 
(3) Mr. Soddy’s book on ‘“‘The Chemistry of the 
Radio-elements ” is the first of a series of “ Mono- 
graphs on Inorganic and Physical Chemistry,” of 
which ten numbers are already announced. The 
idea of the series is excellent, and the monographs 
should appeal to a wider circle and have an even 
larger circulation than the biochemical mono- 
graphs already issued by the publishers. Follow- 
ing a general description of radio-activity and 
radio-active constants, the three “ disintegration 
