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of a book such as this, and in its publication Mr. Crookes 
has rendered an important service to the analytical 
chemistry cf the day. The author’s connection with the 
Chemical News has doubtless afforded him great and 
peculiar advantages in the compilation of the materials 
for his work ; indeed, we notice that not a few of the most 
valuable processes he describes have already appeared in 
that journal. 
Not the least admirable feature in the book (and herein 
it differs from the ordinary run of quantitative manuals) 
is the prominence given to methods for detecting and 
estimating the so-called “rare” metals. Thus we have 
methods given for the extraction and quantitative separa- 
tion of lithium, czesium, and rubidium ; cerium, lanthanum, 
and didymium; glucinum and yttrium, &c. Bunsen’s 
method of analysing platinum ores is also fully described. 
The discoverer of thallium may justly say that if investi- 
gators were more in the habit of looking for the “rare” 
elements, they would doubtless turn up unexpectedly in 
many minerals. 
But for fear that some “practical man ” has already made 
up his mind about the character of this book, we hasten to 
say that by far the larger portion of it is devoted to the 
analytical processes connected with the more important 
metals and their ores. The sections on iron and copper 
are particularly complete, all the newest and best methods 
being minutely described. We may instance Matthies- 
sen’s process for the preparation of pure iron, the Mans- 
field method of copper assay, and Meunier’s methods for 
the immediate analysis of meteoriciron. Under the article 
“ Soda-ash,” attention is very properly directed to the 
absurdity practised in the alkali trade of at one time 
using the old atomic weight (24) of sodium, and at another 
the real number in stating the value of soda-compounds, 
the manufacturer invoicing the strength of his ash in 
accordance with the basis of calculation which he 
knows will be employed in reporting on its quality. 
This custom in many cases amounts to a positive abuse, 
and is a constant source of vexatious complaint between 
buyer and seller. The author quotes an instance in which 
soda-ash of identical quality has been known to be in- 
voiced, part to one customer as containing 48 per cent. 
part to another as 49 percent., and part to a third as 50 
per cent.; the actual percentage being 48}; the separate 
consignments being reported also of these different 
strengths by the analysts in the different towns to which 
the goods were sent. Inasmuch as soda-ash is usually 
valued at so much percent., this amounts to a fraud on 
the purchaser. Surely the Alkali Manufacturers’ As- 
sociation would consult their real interest by putting an 
end to such a petty shamasthis. But after all this is 
only on a par with the iniquitous system of “high” and 
“low” analyses, which is a scandal to the chemistry of 
the day. Apropos of this we would add that those in- 
terested in the agitation which has arisen in certain chemi- 
cal quarters respecting the proper methods for estimating 
superphosphates and phosphoric acid generally, will find 
ample details in this work of the reliable processes which 
have hitherto been devised to that end. Under the head 
of carbon the method of assaying animal charcoal is 
described, and this includes an account of Schiebler’s 
calcimeter and the mode of using it; the account of 
Heinrich’s inquiry into the methods for the proximate 

analysis of coal, which is here introduced, together with the 
blowpipe assay, constitute one of the most complete things 
in the book. 
In the midst of so much that is excellent it may seem 
invidious to seek for real or supposed omissions, but we ven- 
ture to think that a few addenda in a future edition would 
addto the value of thebook. Forexample, Bunsen’s method 
of preparing pure platinum tetrachloride from scrap plati- 
num, and his simple and expeditious method of recover- 
ing this metal from the residues in the process, might be 
an advantageous addition to the condensed description 
by Messrs. Teschemacher and Denham Smith of the 
ordinary method of estimating potash. Without doubt 
not a few of the errors to which a potash determination 
made by this method is liable are due to the use of im- 
pure platinum. A chapter devoted to the description of 
useful or improved forms of apparatus, such as the new 
filter-pump, would also form a valuable addition. Still we 
must not forget to add that Dr. Carmichael’s neat and 
ingenious method of analysis receives its due share of 
attention. Nor do we see the reasonableness of making 
the selection of methods strictly inorganic ; for surely the 
modifications in the process of ultimate analysis intro- 
duced by Mr. Warren cannot constitute the sum of the 
improvements in organic analysis, proximate and ulti- 
mate, which have come under the author's notice. 
But we have said enough to indicate the character and 
scope of this work, and imperfect as our sketch is, it will 
at least serve to show that the book admits of very general 
application. It will doubtless attain to the popularity 
which it merits, and the chemical community will thank 
the author for the worthy contribution he has rendered to 
its literature. T. E. THORPE 


EETIERS ZO TLE EDITOR 
[Zhe Editor does not hold himself responsible for opinions expressed 
by his Correspondents, No notice is taken of anonymous 
communications. | 
The Sun 
In NaTurE for May 18, I find a review by Prof. Newcomb 
of my book on the Sun, and I beg leave to give some explana- 
tions respecting it. It isa pity that Mr. Newcomb has received 
my book only so lately (about one year after the printing was 
finished). On this account the criticism which he makes re- 
specting spectrum analysis and the defects of the work on that 
head is entirely admissible ; but this is no fault of the author. 
Since the book was written sixteen months have elapsed, and 
during this time great progress has been made in this branch of 
science, and nobody knows it better than myself, since I find so 
many things to add to that chapter. 
But the criticism seems not so just when he reproaches the 
work with appearing to undertake to spare the reader the 
trouble of having recourse to elementary books. At the time of 
writing, neither of the valuable books which we have now by 
Roscoe and Schellen were published or had reached me, and 
the common treatises are very scanty in this respect, so that it 
was indispensable then, and perhaps even now, to indicate to 
the general reader the principles of the new science. 
In the rapid progress of discovery, a book becomes old very 
soon, and a reviewer must not forget that printing requires time, 
and that this work appeared at the very moment of the breaking 
out of the war, so that it was shut up in Paris for almost another 
six months. 
But a more serious criticism is that which refers to the tem- 
perature of the sun. As this is a repetition of M. Zéllner’s 
critique, I beg to give some explanation. It is true that I have 
assumed that radiation is proportional to temperature without 
regard to the law of Dulong and Petit, and to the condition of 
