2 
REVIEW OF CERTAIN DOCTRINES 
of other bodies with which they do not combine, and which, 
in some cases, undergo no change themselves. It is to the 
last mentioned mode of reaction that the name above men- 
tioned has been applied. Yet, under this head, processes 
have been associated which have irreconcilable features. 
Thus to the following processes one rationale is given by 
the distinguished chemist of G iessen: the solubility acquired 
by platina by being alloyed with silver —the catalyzing in- 
fluence of platina sponge or platina black — the explosion 
of fulminating powders by slight causes — the reciprocal 
decomposition of bioxide of hydrogen and oxide of silver — > 
the agency of nitric oxide in the generation of sulphuric 
acid — the action of ferments* 
To me it seems that there is a great diversity in the cha- 
racteristics of the processes thus alluded to. In that of the 
alloy there is at least as many atoms of silver in actual com- 
bination with platina, as there are atoms of this metal ; and 
the change which the latter undergoes is precisely the same 
as that to which the former is subjected. 
In the case of platina sponge causing the formation of 
water; or of platina black causing the acetification of alco- 
holic vapour, the inducing agent undergoes no change itself 
nor does it enter into chemical combination either with the 
materials or the products. Liebig ascribes the result in this 
instance, to the alternate absorption and subsequent evolu- 
tion of oxygen by the powder ; since, after exposure to the 
gas, it may; by exhaustion, be made to give up a portion. 
Yet the agency of this metallic mass cannot differ, in this 
case, fro in that in which it causes the pure elements of water 
to combine, and in which, if absorption take place, it is not 
confined to oxygen more than to hydrogen. Again the fact 
* Traite de chimie organique ; Paris, 1840. 
Page xix., last paragraph. 
11 xxvii., Du ferment, paragraph 2d. 
u xxxviii. Acetification, paragraph 2d. 
" 388-9, Acid acetique. 
