1084 
Chemistry. — “On Catalysis”. By NILRATAN Duar. (Communicated 
by Prof. Exnst Conen). Part I. 
(Communicated in the meeting of Nov. 27, 1915.) 
The work on catalysis consists of the following main divisions: 
(1) Release in supersaturated systems. 
(2) Photo chemical actions. 
(3) Pseudo catalysis or induced actions and catalysis in homogen- 
eous systems. 
(1) Release in supersaturated systems. Lrcocq DE BoisBAUDRAN (Ann. 
Chim. Phys. 1866 (4), 9, 173) was the first to show that not only 
were crystal germs of the substance itself able to provoke the 
crystallization of supersaturated solutions, but that also germs of 
such substances as were isomorphous with the substance were able 
to do so. 
GERNEZ (Compt. rend. 1866, 63, 843) showed that not only the 
crystal system required to be the same in order to call for the 
crystallization but also, in the case of crystals belonging to other 
than the holohedral class of any system, that is, crystals showing 
less than the full symmetry of the system, the particular variety 
must be the same. 
J. M. Trouson (Zeit. für Kryst. 1881 6, 94) showed that strict 
isomorphism was essential in the ervstal germ and that the internal 
structure of the germ must be similar to that of the dissolved 
substance. 
Up till now this has been accepted by all scientists. Thus Turron 
in his large volume on Crystallography (1912) states: — “The state 
of supersaturation can be removed not only by the agency of solid 
germs (excessively minute crystals) of the dissolved substance itself, 
but also by the action of solid germ crystals of a substance isomorphous 
with it and possessing close similarity of molecular volume and of 
the molecular distance ratio”. 
Moreover, the power of the release of supersaturation has been 
adopted as one of the tests for the determination of isomorphism. 
In this investigation on many isomorphous substances it will be 
shown that the above test is not generally applicable. 
Hydrated calcium chloride (CaCl,, 6 H,O) is well known to be 
isomorphous with strontium chloride (SnCl,, 6 H,O) but the release 
of a supersaturated solution of calcium chloride cannot be effected 
by strontium chloride. 
Also Reterrs (Zeit. Phys. Chem. 1889, 8, 289, 497; 4, 599) from 
