56 BEPORT— 1870. 



A'ir-]i6llutlon from Chemical Worlcs. By Alfkeb E. Fletcher, F.C.S. 



On tlie Utilization of Seivage, iviili special reference to the Phosphate Process. 



By Davib Foebes, F.B.8. 



It was stated that sewage irrigation was tlie only process which had as yet uti- 

 lized the entire liquid as well as the solid contents of the sewage. As, however, 

 there are many cases in which sewage irrigation is neither applicable nor advan- 

 tageous, it is desirable that some chemical process should be sought for by which 

 the sewage could be so far purified by precipitation that the supernatant water 

 could be allowed to run off directly into rivers without danger to health or animal 

 life, whilst the precipitate should be of so high a value as manure as to pay for its 

 transport to a distance for the use of the agricidturists. The experiments made 

 already on the London sewage by the phosphate process, and on the present occa- 

 sion successfully repeated on a small scale before the audience with Livei-pool 

 sewage, appear to fulfil in a gi-eat measure these conditions. This process, brought 

 forward by the author in conjunction with Dr. A. Price, is based upon the fact 

 that certain mineral phosphates, when in a freshly precipitated state, eagerly com- 

 bine with both organic matter and ammonia in sewage. The process required 

 nothing beyond a reservoir containing the sewage, to which the phosphates (in 

 major partof alumina) are added, preferably in the state of solution in hydro- 

 chloric or sulphuric acid, from which, by the addition of a little milk of lime 

 (just sufficient to neutralize the acid which holds them in solution), they are at 

 once precipitated, along with the organic matter and part of the ammonia in the 

 sewage. The deposit subsides rapidly, and leaves the water clear and colourless, 

 even if tinctorial substances of great power are present : in the experiments shown, 

 ink was added to the Livei-pool sewage, but the colouring-matter was instantly 

 removed along with the precipitate. The effluent water obtained by this process 

 is, of course, not any thing like so pure as water ordinarily supplied for drinking- 

 purposes ; still the water from the London sewage at Barking Creek, so purified, 

 could, as was shown, be drunk without repugnance, fishes could live in it, and it 

 had remained free from offensive smell for months, during the entire hot summer 

 of last year, without any tendency to'putrefy or emit any disagreeable odour. With 

 regard to the value of the precipitated manure, it was admitted that no known 

 chemical substances could precipitate from sewage the whole amount of substances 

 valuable for agriculture ; and it was only claimed that so much of them had been 

 extracted as to leave the effluent water innoxious, whilst one of the most impor- 

 tant featui-es of the process, in which it differs from all the others, is, that all the 

 substances employed in the purification augment the agricultural value of the pre- 

 cipitated manure, and thus render it of such value as to enable it to bear the cost 

 of transport to a distance. 



On the Action of Sulphurous Acid, in Aqueous Solution, on Phosphates and 

 other Compounds. By Dr, B. W. Geelanb. 



Sulphurous acid in aqueous solution dissolves various phosphates without 

 decomposing them, even when the oxide forms with sulphurous acid an insoluble 

 compoimd. In this respect the tribasic phosphate of lime is particularly interest- 

 ing. By means of sulphurous acid a solution of 1'3 sp. gr. can be obtained. This 

 keeps very well in the cold; but a rise of the temperature to 19° determines the 

 gradual precipitation of sulphite of lime. If the solution is quickly heated, a com- 

 pound corresponding to the formula 300, PO3, SOj, 2II0 is fonned, which sepa- 

 rates as a white crystalline powder, and is characterized by great stability. It is a 

 powerful disinfectant and an active manure. The solution gives dibasic phosphate 

 of lime by boiling imder reduced pressure, by standing in vacuum, and by mixing 

 with alcohol. 



The dibasic phosphate of lime is also easily dissolved by sulphurous acid. The 

 solution again deposits the original phosphate when the sulphurous acid is removed. 



The phosphates of manganese and magnesia form strong solutions with sul- 

 phurous acid, from which the original phosphate can be again obtained. The phoa- 



