NATURE 
ult 
THURSDAY, MAY 2, torz2. 
CHEMICAL SPECTROSCOPY. 
Introduction & l'Etude de la Spectrochimie. Par 
Prof. G. Urbain. Pp. iii+248+ix plates. 
(Paris: A. Hermann & Fils, 1911.) Price 
1o francs. 
| ara URBAIN has written an exceedingly 
interesting and valuable introduction to 
spectroscopy treated more especially in relation 
to chemistry and chemical analysis. He has 
based this book upon his course of lectures de- 
livered at the Sorbonne, and with undue modesty 
explains that it is mainly written for those 
younger chemists who, in their desire to enter 
a field full of promise, wish rapidly to acquire | 
the fundamental ideas necessary for the theoretical 
and experimental study of the subject. Prof. 
Urbain is singularly happy in his preface, wherein 
he deals with the position of the spectroscope in 
relation to chemistry. Quite truly he points out 
the very valuable services that spectroscopy has 
rendered to chemistry and to astronomy. As for 
the former, it was a very long time before the 
subject formed more than a very restricted 
adjunct to chemical analysis. In truth, spectro- 
scopy now deals with numerous facts which have 
but a dim connection with chemical analysis, and 
it deserves to rank as one of the principal branches 
of physical chemistry along with electrochemistry 
and thermochemistry. 
The discoveries that chemistry owes to spectro- 
scopy are many. To all is familiar the detection 
of rubidium and cesium by Bunsen and Kirch- 
hoff, followed by the isolation of indium, thal- 
lium, and gallium. The spectroscope, however, 
has also proved itself to be the only guide in 
that apparently insoluble labyrinth of elements, 
the rare earths. To the spectroscope we owe 
the discovery of samarium and-dysprosium by 
Lecoq de Boisbaudran, of holmium and thulium 
by Soret, of neodymium and praseodymium by 
Auer von Welsbach, and of europium by Crookes 
and by Demarcay. Finally there is the brilliant 
work of Prof. Urbain himself, which has resulted 
in the separation of ytterbium into neoytterbium 
and lutecium, and the discovery. of the new 
element celtium. Again, the value of the spectro- 
scope in Ramsay’s work on the rare gases is 
within the common knowledge of all. Modern 
chemistry would have been in debt to the spec- 
troscope for its most beautiful discoveries had 
not M. and Mme. Curie found in radioactivity 
a method of investigation which, although less 
NO. 2218, vor. 89} 
general in its application, is certainly more sensi- 
tive in certain cases. 
When Bunsen and Kirchhoff published their 
method of investigation by flame _ spectra, 
chemists naturally welcomed this with enthusiasm. 
Ever since that time the textbooks of analysis 
have religiously incorporated their methods. 
Very few, if any, of these books describe the 
| modern methods of investigation, although the 
value of these has clearly been proved. These 
modern methods are only to be found in special- 
ised books which students have not the leisure 
to read and the skilled chemist rarely consults. 
Prof. Urbain shows how the confidence felt by 
chemists in spectroscopy received a severe blow 
when the plurality of spectra was enunciated by 
Pliicker and Hittorf. It was felt that spectrum 
analysis no longer possessed that rigour and in- 
fallibility at first attributed to it; nothing, after 
all, was so sound as the good old methods of 
pure chemistry; spectrum analysis was a com- 
plex subject, and it was abandoned to the speci- 
alist. In spite of this attitude of the pure 
chemist, the advance of spectro-chemistry has 
been enormous, and the variety of the modern 
methods is extraordinary. Flame spectra, spark 
spectra, spectra of gases and of solutions, arc 
spectra, absorption spectra, phosphorescent 
spectra, and infra-red emission and absorption 
spectra—all have their value in particular cases. 
The time has surely come for this subject to 
take the rank which it deserves in the chemical 
laboratory. At present the students of chemistry 
have a poor idea of the part played by the spec- 
troscope in analytical research. The faint-hearted 
ones hesitate to take risks in so unknown a field, 
while the bolder ones perhaps try a few experi- 
ments, but are soon discouraged owing to their 
ignorance of the technique. 
With the view of removing this ignorance, 
Prof. Urbain has written this book, and he treats 
in a most admirable way all the modern methods 
of work. In the first four chapters he describes 
the character and nature of spectra and the 
methods of illumination. Without going fully 
into the spectroscope itself, he gives in detail 
a most excellent account of the modern methods 
of illumination. The fifth and sixth chapters deal 
with phosphorescence and absorption, to the 
literature of which the author himself has con- 
tributed so largely. In the seventh chapter is to 
be found a concise description of series of lines 
and their relationships. 
In fine it may be said that this book forms 
a most admirable introduction to chemical spec- 
troscopy, and it is to be cordially recommended 
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