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POPULAR SCIENCE REVIEW. 
be said of much of the chemistry of the so-called aromatic compounds ; it 
dates from the time when there was a commercial demand for coal-tar 
products. We do not of course wish to underrate the influence of Kekule’s 
theory of the constitution of these substances, without which we might still 
be groping in the dark. The volume before us gives the preparation, puri- 
fication, and valuation of anthracene, its conversion into anthraquinone 
and the sulpho-acids. The various processes for the preparation of artificial 
alizarine are carefully described, and the difficulties involved are mentioned. 
The methods best adapted for preparing pure specimens in the laboratory 
are given, as well as those commercially practicable. According to the now 
accepted formula of anthraquinone, there are nine possible compounds 
isomeric with alizarine ; and of these eight are actually known, though 
scarcely with sufficient accuracy. These are, anthraflavic acid, iso-anthra- 
flavic acid, anthraxanthic acid, quinizarine, chrysazine, frangulic acid, 
xanthopurpurine, and isalizarine. Some of these are capable of dyeing mor- 
danted tissues. From what is known of their constitution, it seems pro- 
bable that only those derivatives of oxy anthraquinone are dyes which have 
two hydroxyl groups situated in the same benzole nucleus. To a student this 
work is suggestive of much research, but it requires that one should know 
something of organic chemistry to appreciate its value. An evident misprint, 
ferrous for ferric salts, occurs on page 157. We are much indebted to the 
translator for bringing into notice and making easily accessible the immense 
fund of scattered information collected in Mr. Auerbach’s valuable work. 
ZOOLOGICAL CLASSIFICATION.* 
I T is not an easy task to compress a whole system of zoological classifica- 
tion into a volume small enough to be conveniently carried in the 
pocket ; but this is what Mr. Pascoe has attempted to do, and it must be 
confessed with a very considerable amount of success, in a little work just 
published under the above title. As a matter of course the reader need not 
look for an exhaustive treatise on zoology in a book containing only about 
200 very small octavo pages, and indeed the author himself makes no claim 
to have produced anything of the kind, his object being, as he tells us in his 
preface, to furnish u a convenient work of reference on the classification of 
the animal kingdom, and to bring the contents of the various groups under 
the eye in the most concise form.” 
This modest purpose Mr. Pascoe has certainty fulfilled in a very credit- 
able manner. His little book is an excellent work of reference ; for 
although, perhaps, it would not be possible for a beginner to take it up and 
learn much zoology from its pages, the student, as he progresses, will find it 
a most excellent aid in correlating the knowledge that he acquires, in 
determining the relations and the precise position in the animal kingdom of 
* “Zoological Classification : a Handy Book of Reference, with Tables of 
the Subkingdoms, Classes, Orders, &c. of the Animal Kingdom, their 
Characters, and Lists of the Families and principal Genera.” By Francis 
P. Pascoe, F.L.S., &c. Small 8vo. London : Van Voorst. 1877. 
