Chemistry. — “Catalysis” — Part VII — Notes on Cutalysis m 
heterogeneous systems. By Nm Ravas Daar (Communicated 
by Prof. Easer Comms). 
(Communicated af the meeting of November 29, 1919). 
1. Ithas been known for a long time that violet ehromie chloride is 
practically imsolable im water, bat im presence of reducing agents 
solution takes place due to the transformation into the soluble 
modification. 
Anhydrous ferrie sulphate dissolves slowly im water at the ordi 
Gary temperature, im other words, it may be said to have a small 
velocity of solutioa. 1 have found that reducing agents hike stannous 
chlemde, ferrous sulphate, salphurous acid ete, markedly accelerate 
the velocity of soluttiom of ferrie sulphate im water. 
Im the ease of chrome chloride, it is assumed that the reducing 
agemit first reduces the imsoluble chromie chloride to chromous 
chloride, and the orginal chromous chloride is transformed into 
soluble chromie chloride. The newly formed chromous chloride them 
acts om the mseoeluble chromic chloride as before 
The diffieuliy of am explanation like this is that we assume thaf the 
reducing agent acts om the solid chromie chloride and reduces it; 
from oor experience im heterogemeous systems, we know how diffi- 
ealt it is to redme a solid substance rapidly with a solutiom of a 
reducing agemt. . 
Moreover, im the ease of ferrie sulphate we do not know two 
varieties of the salt as im the ease of chromic chloride 
Tt is dificult to assume that ferrous salphaie would reduce ferrie 
sulphate, for we kmow that a mixture of ferrie and ferrous salts 
eam exist unchanged for am indefinite period im absence of oxygen. 
So we cam say with Osrwarp (Grundlimiem der anorganischen 
Chemie, Leipzig 1900; A. Frspnar’s trans. 603, 1902) that a sufficient 
explanaiiom of these actions is still wanting 
2. The action of mitrie acid om the metals generally, is somewhat 
complex, because the maim reactiom is complicated by side or con 
carremt, amd by consecutive reactions. These again depend not only 
upon the particular metal under consideration, but also om the 
