272 AprenEY—Dissolved Gases and Fermentative Changes. 
OricIn oF THE OrGanic Marrers (Humus) EXPERIMENTED WITH. 
I have already made some reference to this humus in a short Paper published 
in the ‘‘ Scientific Proceedings” of this Society.* It was found in some sewage 
sludge which had been allowed to ferment for some time under what were 
practically aérobie conditions. The sludge had been obtained from a sewage 
purification works, in which the coarser portion of the solid matters in suspension 
in the sewage were first separated by mechanical subsidence ; the sewage was then 
mixed with a water solution of manganate of soda; the peroxide, which separated 
out, was allowed to subside, together with the matters remaining in suspension in 
the sewage, to the bottom of the tank in which the operation was conducted. It 
was finally drawn off from the tank in the form of a mud, I obtained several 
hundredweights of this mud, and first drained it on a gravel bed, and, when of 
sufficient consistence, I made it up into a large heap, and allowed it to slowly 
air-dry in a covered shed. After being left in this condition for about three 
months, I found the interior portions had assumed a grey colour, and were still 
wet and clay-like in consistence; only those portions of the heap immediately 
exposed to the air had retained the original brown colour of the peroxide. 
Some small lumps were detached from different parts of the interior of the 
heap, and allowed to completely air-dry ; an average portion was then analysed. 
The results of the analyses are given in the Paper above referred to (p. 250), and 
it will only be necessary to quote here the main results. They are :— 
Percentage. 
Insoluble mineral matter and silica, . A E 5 16°66. 
Moisture, . 5 Seer 5 é : : 15°68. 
Organic matter, ‘‘solublein HCl,” . ¢ 3 . 4°35. 
- ‘‘insoluble in HCl,” : : : 4:00. 
MnO:"\) iniyitsem ew ROVE like Webel? NE geo d3G0F 
(NH,).0,f . ‘ 0-005. 
CaO, Fe,03, Al,0O;, MgO, eee 
Na,O, K,0, NiO, CoO, ZnO, ; 
CO., SPORT ye gL VENTLA OM AO See) SA Om esa 
‘SO, ‘P205, ‘Cl, 2 : é ; . 3 : 0:96. 
100°695. 
The above results show that the manganese was present as manganous 
too) 5 
carbonate: a careful examination was made for peroxide, but with negative 
results. 
* «On the Reduction of Manganese Peroxide in Sewage,”’ vol. vit., N.S. (1894), p. 247 
+ The NH, in the wet mass, before complete air-drying, amounted to 0:014 per cent. (calculated on the 
wet mass which contained about 60 per cent. moisture), 
