Notices respecting New Books. 149 
A large portion of the work is devoted to the consideration of the 
laws of the absorption of gases in liquids, the methods of determining 
the coefficients of absorption, and numerous examples showing the 
coefficients of a considerable number of gases. A most valuable result 
of the perfection to which the determination of the coefficients of ab- 
sorption can be carried, and one that cannot be too highly appreciated 
by chemists, is, that it enables us to ascertain whether a gas under 
examination is a mixture in atomic proportions or a truly chemical 
compound. It is well known to all who have paid any attention to 
this branch of chemistry, that Frankland and Kolbe have proved that 
eudiometri¢ analysis (as might be expected) was incapable of show- 
ing the difference between two volumes of marsh-gas and equal 
volumes of hydrogen and methyle. Any process capable of throwing 
light on questions so difficult of solution will doubtless be thankfully 
received by chemists. Ia the work before us, Bunsen shows how 
perfectly the question may be solved by the method alluded to, even 
in cases like the present, where the greatest difficulty might have 
been anticipated, from the fact that the differences in the coefficients 
of absorption are very little. The result obtained by the absorptiome- 
tric method clearly indicates that marsh-gas, prepared by heating 
together the acetate with hydrate of potash, and purified by means 
of fuming sulphuric acid and potash, is not a mixture of methyle 
with hydrogen, nor an isomer of natural marsh-gas, but the same 
substance which is evolved by the mud volcanoes of Bulganak in the 
Crimea. 
The author has incorporated in his work the results of the re- 
searches which he made some years ago (in conjunction with Prof. 
Stegmann) on the laws of the diffusion of gases. As usual, the ap- 
paratus employed and the manipulation generally are both novel and 
ingenious. 
He deduces several facts from his experiments ; among others, 
that the pores of the gypsum diaphragms do not act towards gases 
passing through them as a system of fine openings in thin plates, 
but as a system of capillary tubes. He has also made elaborate ex- 
periments to solve several other important questions, among which 
the following stands prominently forward :—‘‘Do the volumes of 
two gases which have diffused into each other, stand to each other, 
as is universally admitted, inversely as the square roots of their den- 
sities ?” To our surprise we find that a negative answer is returned 
to this question. We do not feel it necessary to enter into a detailed 
account of the author’s experiments and deductions, as he admits 
this portion of the investigation to be still in an unfinished state. 
A very important portion of the volume, and one which wiil be 
read with interest by all who are engaged in eudiometry, is on the 
phznomena of the combustion of gases. The author considers in 
this, the last portion of the work,—the heat of combustion—the tem- 
perature of the combustion—the explosive force of gases—and the 
temperature of ignition of gases. Several other instructive and in- 
teresting properties of gases are studied incidentally, such as their 
diathermanous properties, and the influence of diluents ; moreover, 
