88 
Proceedings of Royal Society of Edinburgh . [sess. 
The Action of Silver Salts on Solutions of Ammonium 
Persulphate. By Hugh Marshall, D.Sc., and J. K. H. 
Inglis, M.A., B.Sc. 
(Read February 17, 1902.) 
In a paper already communicated to the Society by one of us* 
attention was drawn to the fact that, in presence of a soluble 
silver salt, ammonium persulphate is decomposed with formation 
of nitric acid as well as sulphuric acid. The action had at that 
time been studied only in a roughly quantitative way, and it was 
therefore thought that a more exact study of the velocity of the 
reaction, and of the influence exerted by other salts present in 
solution, might prove of interest, and also throw light on the course 
which the reaction follows. 
As stated in the paper already referred to, the reaction appears 
to be expressible by the equation — 
(a) 4(NH 4 ) 2 S 2 0 8 + 3H 2 0 = 7NH 4 HS0 4 + H 2 S0 4 + HN0 3 , 
but it was found that the rate of change corresponded approxi- 
mately to that of a monomolecular reaction, indicating that the 
reaction takes place in several stages, one of which being much 
slower than the others, determines the velocity. If the above 
equation is written in the form — 
(&) NH 4 ' + 4S 2 0 8 " + 3H 2 0 = 10H‘ + 8S0 4 " + N0 3 ' , 
it is evident that the reaction could not be monomolecular. But 
if the intermediate formation of silver peroxide is assumed (and 
there are good grounds for the assumption), the reaction is divisible 
into the two stages represented by the following equations — 
(c) S 2 0 8 " + 2 Ag' + 2H 2 0 2S0 4 " + 4H* + Ag 2 0 2 ; 
(d) 4Ag 2 0 2 + NH/ + 6H‘=^: 8Ag* + N0 3 ' + 5H 2 0 . 
Neither of these is actually monomolecular. But we may consider 
the concentrations of the Ag' and the Ag 2 0 2 as being constant, if 
the concentration of the total silver is small compared with the 
* Marshall, Proceedings , vol. xxiii. p. 163. 
