Chemistry. — ‘Catalysis — Part XII. Some induced reactions and 
their mechanisn’’. By Nit Ratan Duar. (Communicated by 
Prof. Ernst COHEN). 
(Communicated at the meeting of January 29, 1921). 
When an aqueous solution of mercuric chloride is boiled with 
oxalic acid, there is no reduction of the mercuric chloride to the 
mercurous state, but as is well known this mixture of mercuric 
chloride and oxalic acid decomposes at the ordinary ple in 
sunlight according to the equation, 
2HgCl, + H,C,0, = 2HgCl + 2HCI + 2C0,. 
The same change, however, takes place in the dark as the author 
has observed if a few drops of a deci-normal potassium permangan- 
ate are added to the mixture. As soon as the color of the per- 
manganate is discharged, mercurous chloride begins to separate out. 
This phenomenon appears to be of general occurrence. Thus the 
reduction of mercuric chloride and bromide by oxalic acid, tartaric 
acid, citrie acid, malonic acid, malic acid, glycollic acid, cane sugar, 
glycerine, lactic acid, hydroxylamine bydrochloride, hydrazinehydro- 
chloride ete., the reduction of gold chloride by several reducing © 
agents, the reduction of silver nitrate, cupric chloride and selenious 
acid (to selenium) by various organic acids, cane sugar etc. are 
promoted by the addition of such oxidising agents as potassium 
permanganate, potassium persulphate, manganese dioxide, potassium 
nitrite, hydrogen peroxide, ceric salts etc. 
It is a remarkable fact that this effect is particularly noticeable 
in those reactions which are sensitive to light. 
In all these instances, chemical changes are taking place in a 
homogeneous system. I have also investigated several cases of induced 
reactions taking place in heterogeneous systems, and I have made 
a special study of oxidations effected by oxygen of the air. The 
following are some of the experimental results obtained: 
