Notices of Boohs. 
[April, 
278 
Deville and Troost discovered that certain gases penetrated tubes 
of iron and platinum, and this fadt led Mr. Graham to enquire 
whether the penetration was not preceded by an absorption of 
the gas. His results proved that palladium, platinum, and iron 
did absorb hydrogen. Palladium, for instance, absorbs nearly 
1000 times its volume of the gas, and most metals appear to have 
the power of selecting one or more gases in virtue of their 
colloidal charadler ; for crystalline metals, such as osmium and 
iridium, do not occlude gas at all. The absorption of hydrogen 
by palladium led him to conclude that the gas was condensed 
into the metallic state ; but, although much evidence was ad- 
duced, it may be doubted whether the metallic charadler of 
hydrogen was established. 
Under the second classification of the papers, the research on 
“ Arseniates, Phosphates, and Modifications of Phosphoric 
Acid,” occupies a prominent place. It commenced with the ex- 
planatory hypothesis that phosphoric acid is disposed to unite 
with 3 atoms of base, and he then traced the method by which 
the metaphosphates and pyrophosphates were produced. It is 
impossible to overrate the importance of this research, for on it 
the theory of the polybasity of acids mainly rested. 
The diffusion of gases appears to have led to the study of the 
diffusion of liquids, and in 1849 the splendid monograph on the 
latter subject was published, the results of which showed that 
diffusion supplied the densities of a “ new kind of molecules,” 
for in liquid diffusion we appear to deal no longer with chemical 
equivalents or Daltonian atoms, but with masses even more 
simply related as to weight. By continuing the investigation he 
was enabled to divide various soluble substances into crystalloids 
and colloids, the former having a rapid diffusion rate and the 
latter being marked by low diffusibility. He pointed out that, 
although chemically inert, in the ordinary sense, colloids possess 
a compensating adlivity of their own, arising out of their physical 
properties. The colloid is, in facft, the dynamic state of matter, 
the crystalloid being the statical condition. The colloid 
possesses energy, and it may be looked upon as the primary 
source of the force appearing in the phenomena of vitality. 
His paper on “ Speculative Ideas concerning the Constitution 
of Matter ” will always be viewed with special interest, as it con- 
tained several remarkable expressions of belief, such as the 
suggestion that the various kinds of matter recognised as 
different elementary substances may possess one and the same 
ultimate or atomic molecule existing in different conditions of 
movement. With the atom at rest, the uniformity of matter 
would be perfedl : but it always possesses motion due to a pri- 
mordial impulse, and, as differences in the amount of this motion 
occasion differences of volume, matter only differs by being lighter 
or denser matter. The gaseous molecule is composed of a group 
of the preceding inferior atoms, following similar laws, and is thus 
