Aprney—On the Reduction of Manganese Perowide in Sewage. 251 
the dilute acid employed for dissolving the substance. Practically, 
however, all was left undissolved when the solution was evaporated 
to dryness, and the residue treated with concentrated hydrochloric 
acid and water, in the ordinary way, for the separation of soluble 
silica. The organic matters which were separated in this way 
were brownish-black in colour, and were largely soluble in a dilute 
solution of sodium carbonate, giving rise to a solution of a deep 
brown colour. ‘T'hey seemed, in fact, closely associated in chemical 
and physical characters with the colouring matters of peat, and 
also with the colouring matters which are formed where soluble 
sewage-matters are oxidized by microbes in the presence of an 
excess of atmospheric oxygen. I must, however, reserve a full 
consideration of these colouring matters for a further communica- 
tion. The influence which the peroxide of manganese appears 
here to exert on the products of fermentation of the organic 
matters with which it was associated, and the reduction and 
conversion into carbonate which itself undergoes, leads, I think, 
fairly to the conclusion that the decomposition of the peroxide 
under the conditions described, may be regarded as a fermentation 
consisting of the direct oxidation of organic carbon at the expense 
of the available oxygen of the peroxide ; that, in fact, the insoluble 
peroxide exerts, when mixed with solid fermentable matters, an 
influence, and undergoes a change, precisely analogous to the 
influence and change which nitre undergoes when present in a 
liquid nutrient medium in which either of the two organisms, 
Bacterium denitrificans, a and (3, are allowed to grow. 
T ought to state that Dr. H. J. M‘Weeny, Professor of Pathology 
and Bacteriology in the Catholic University School of Medicine,. 
has already commenced a bacteriological study of the organisms 
which are associated with the reduced peroxide which I have above 
described. 
I cannot conclude without expressing my warm thanks to 
Mr. James Carson, Assoc. R.C.Sc.I., for the skilful assistance 
which he has rendered me in carrying out the analytical portions 
of the work embodied in this Paper. 
