July 23, 1870.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
71 
sewage will effect the speedy separation of all the sus- 
pended matters, and also about one-fourth of the dis¬ 
solved organic matter, leaving a clear liquor which has 
lost a great part of its offensive odour; and when the clear 
liquor is mixed with from five to seven times its bulk of 
water, and is exposed to the air, it is no longer offensive.” 
At Leicester, where the lime method has been adopted, 
the river Soar, into which the sewage flows, has under¬ 
gone a remarkable improvement. Before the works were 
established the river was most offensive, the fish were 
killed, the vegetation of the river was destroyed, and 
those who inhaled the effluvia from it were constantly ill. 
At the Belgrave Mill, which is just below the point 
where the sewage enters the river, the foulness of the 
stream was such that in summer-time the water of the 
mill-dam appeared to boil with putrefaction ; the stench 
from it was intolerable, and so large was the quantity of 
sulphuretted hydrogen evolved, that the silver in the 
men’s pockets turned black in a few hours. At that time 
the men were constantly afflicted with diarrhoea, they 
lost their strength, and their appetites always failed 
them; one man only out of thirty men in eighteen years 
had been able to stand it, and he it was who gave me an 
account of the matter. Now, however, and for the last 
three years since the lime process has been adopted, the 
river presents an entirely different appearance—aquatic 
plants have begun to flourish, the fish have ventured to 
return, the black mud has ceased to accumulate, and the 
mill-dam is no longer offensive. All along the stream 
the people speak of the change with satisfaction, and it 
would appear that the process fulfils the requirement of 
the local Act, which demands that the water discharged 
from the works shall not occasion a nuisance, or be inju¬ 
rious to the health of those who live or are employed on 
the banks of the stream. 
Crude sulphate of alumina is another precipitating 
agent. It is employed at Stroud, in Gloucestershire, in 
what is known as Bird’s method. The crude sulphate is 
made by adding about 20 lbs. of sulphuric acid to 1 cwt. 
of powdered clay, and allowing it to stand for some time. 
This material is mixed with sewage in the proportion of 
1 cwt. to from 20,000 to 30,000 gallons of sewage, and 
the sedimentary matters are collected in a properly-con¬ 
structed tank. Sulphate of alumina is decomposed by 
the ammonia of the sewage, and the alumina flocculates 
and precipitates the suspended matters, leaving a clear 
supernatant liquid, from which a good deal of dissolved 
organic matter has been removed. 
To ensure the precipitation of the alumina, Dr. Ander¬ 
son, of Coventry, recommends the addition of lime. He 
uses about one pound of crude sulphate to every 100 
gallons of sewage. This mixture is well agitated, and then 
a quarter of a pound of lime in a creamy condition is 
added. Again it is agitated, and the flocculent alumina, 
together with the suspended matters, rapidly falls. The 
sediment is collected in subsiding-tanks, which are 
worked alternately, and the clear liquor is run off from 
it. As in the last case, the suspended matters are en¬ 
tirely removed, with a considerable amount of the dis¬ 
solved organic matter. 
Chloride of iron, with lime, is also a powerful defeca¬ 
tor. It was formerly used at Northampton, and is still, 
to some extent with lime,—the lime being first added to 
the sewage in the proportion of about a bushel to 8500 
gallons of sewage, and the chloride of lime to the ex¬ 
tent of about half a gallon! The chloride is made at 
the works, and contains about 9500 grs. of the mixed 
chlorides of iron per gallon. In this case also the pre¬ 
cipitation of the sewage is very complete. At present, 
however, the local authorities are using sulphate of iron 
and alumina instead of the chloride. The compound is 
made by mixing 3 cwts. of crude sulphuric acid -with 
2 tons of a ferruginous earth obtained in the neighbour¬ 
hood. After standing for a few days the mixture is 
ready for use, and it is added to the sewage in the above 
proportion to a million gallons of sewage. 
At Leamington, where there is an injunction against 
the discharge of unpurified sewage into the river Learn, 
the authorities have resorted to the use of the “A. B. C.” 
process of Mr. Sillar, which is worked by the Native 
Guano Company at its own cost. The sewage flows to 
the works by gravitation, and there it is mixed with the 
A. B. C. material (consisting of alum, clay, sulphate of 
magnesia, bone ashes, wood charcoal, and a little blood 
diffused through -water). The material is added to the 
sewage in the proportion of 1 gallon to 200 gallons of 
sewage, and the whole of it well agitated. It then 
flows through subsiding-tanks, where the precipitated 
matters subside, and the clear water flows off from a 
weir into an outfall channel with a filter. The tanks 
are worked continuously for about a week, when the 
precipitated matter is removed to a centrifugal machine, 
and drained to the consistence of putty. This is further 
dried by exposure to the air, and its ammonia is fixed 
by means of a little sulphuric acid, which also breaks up 
the organic matter. In this state it is riddled, and sold 
freely at a good profit for manure. 
Samples of the Leamington sewage were taken for 
examination by the Royal Pollution Commissioners on 
the 11th of December last, and duplicates of them were 
furnished to me on the following day for analysis. I 
ascertained that the original sewage contained 66 grs. of 
solid matter in solution per gallon, of which IP43 grs. 
were organic, while the effluent water before filtration 
contained 67 grs. of soluble matter per gallon, of which 
11‘27 grs. were organic, and the filtered water contained 
61 grs. per gallon, of which 7’58 grs. were organic. 
Again, the suspended matters in the original sewage 
amounted to 113-6 grs. per gallon, while in the effluent 
sewage before filtration it was 7 - 64 grs., and in the 
filtered sewage 3-12 grs. The Royal Commissioners, in 
describing their results, do not mention the filtered 
water, but in other respects their results accord pretty 
closely with mine. 
Lastly, there is a method of the late Mr. Blyth, which 
is very deserving of attention. Mr. Blyth was the che¬ 
mist of the old Board of Health, and he had great 
opportunities of studying this matter. His plan is first 
to add a soluble phosphate of lime and sulphate of mag¬ 
nesia to the sewage. After agitation, the mixture is 
neutralized by means of a little slaked lime, and the pre¬ 
cipitated magnesian phosphate carries down with it the 
whole of the sedimentary matter, and a portion of the 
soluble ammonia. A million tons of sewage require 
about 1 ton 3 cwts. of Blyth’s compound, and 4 cwts. of 
lime for neutralizing. The resulting dry precipitate 
weighs about 3 tons 8 cwts., and contains about 58 per 
cent, of organic matter (yielding 4-5 ammonia) and 8-66 
of phosphate of lime. 
All these methods are manifestly capable of separat¬ 
ing from sewage all the sedimentary matter, and also of 
removing considerable portions of dissolved organic 
matter; but to be effective there should not only be 
good agitation of the sewage after the addition of the 
precipitating agent, but there should also be sufficient 
tank-room for the deposition of the sewage for not less 
than four hours; and there should also be a means of 
filtering the defecated sewage before it is discharged 
into the river or other watercourse. 
After witnessing the action of lime as a defecator at 
Leicester and Hertford, Dr. Odling, Dr. Frankland, and 
myself reported to the Thames Conservancy that the 
following were the conditions necessary to its success :— 
1. The proportion of lime should not be less than one 
ton to a million gallons of sewage, and there should also 
be used 56 lbs. of chloride of lime. 
2. That the mixture of the sewage with the lime and 
chloride of lime should be very complete, and that the 
mixture should be agitated, so as to aggregate the sus¬ 
pended matters, and thus assist in the subsequent preci¬ 
pitation of suspended matter. 
3. That the sewage when thus treated with lime 
