236 Analyses of Books. [April, 
certainly important to the student, seeing that almost all che- 
mical operations are performed in its presence, and the results 
are often modified in consequence of its adtion. But it may, we 
think, be fairly questioned by what right a substance admitted to 
be a mere mechanical mixture comes to be described among ele- 
mentary bodies and their compounds. It might also be asked 
whether the first argument given to prove the air to be a mixture 
— viz., the inconstancy of its composition — can be taken as valid. 
It is conceivable that a definite chemical compound might be 
mixed with a variable excess of one of its constituents. In that 
case the ultimate analysis of the whole might fluctuate slightly, 
though we should be dealing with a compound somewhat con- 
taminated. 
The author observes that in tropical countries the oxygen of 
the atmosphere has been observed to drop suddenly as low as 
20*3 per cent, This phenomenon, we understand, is not confined 
to tropical countries, but has been observed as far north as 40°, 
being attended by winds blowing in divergent directions from the 
place where the anomaly was recognised. 
We are glad to note that the author calls attention to the true 
respiration of plants, — a process often overlooked in chemical 
manuals, because masked by assimilation of carbon. The reader 
is also taught that not all plants, but merely such as possess 
chlorophyll cells, are able to decompose the carbon dioxide of 
the air. 
A very curious experiment here described is the liberation of 
hydrofluoric acid from pounded teeth, — say of sheep, — thus 
proving the presence of fluorine in the animal system and infer- 
entially in vegetation. 
The work may safely be recommended as clear, and it is 
scarcely needful to add accurate in its teachings. 
A Systematic Handbook of V olumetric Analysis : or, the Quan- 
titative Estimation of Chemical Substances by Measure, 
applied to Liquids, Solids, and Gases, adapted to the require- 
ments of Pure Chemical Research, Pathological Chemistry, 
Pharmacy, Metallurgy, Manufacturing Chemistry, Photo- 
graphy, &c., and for the Valuation of Substances used in 
Commerce, Agriculture, and the Arts. By Francis Sutton, 
F.C.S. Fourth Edition, London : J. and A. Churchill. 
Both volumetric analysis and the work before us have undergone 
noteworthy changes since the appearance of its first edition. 
Many procedures have been improved, many substances have 
been found capable of volumetric determination which twenty 
