pen sy 
XXVII. 
ON THE REDUCTION OF MANGANESE PEROXIDE IN 
SEWAGE. By W. HE. ADENEY, Assoc. R.C.Se.1., F.C.8., 
F.I.C., Curator in the Royal University, Dublin. 
[Read Frsruary 21; Received for publication Marcu 2; Published Aprim 9, 1894.] | 
SomETIME ago, when studying the action of potassium perman- 
ganate on sewage, I noticed that freshly-precipitated peroxide of 
manganese, when left immersed in a comparatively large bulk of 
sewage for four or five days, becomes completely reduced to 
manganous carbonate. 
The reduction may be shown in an interesting way by mixing 
in a large glass beaker four or five litres of sewage with a suffi- 
cient quantity of a water-solution of potassium permanganate to 
give itadeep pink colour. ‘The permanganate rapidly decomposes, 
and a precipitate, consisting chiefly of peroxide of manganese in 
a hydrated form, collects in large flakes on the sides and bottom 
of the beaker. If, now, the beaker and its contents be allowed to 
stand for four or five days, the peroxide of manganese, especially 
the portions deposited on the sides of the vessel, may be observed 
to slowly change to a yellowish-white colour. On examination of 
some of the yellowish-white substance, obtained as just described 
it was found to consist of manganous carbonate, associated, as was 
to be expected from the nature of the liquid in which it was 
immersed, with swarms of minute organisms. 
When we consider the chemical characters of the peroxide 
obtained in the manner described, it seems impossible to avoid 
the conclusion that it owed its reduction to manganous carbonate 
or the influence of some at least of the organisms growing in the 
