ON TUB THEATJIENT AND UTILIZATION OF SEWAGE. 



Examination of the precipitate after drying it at 100° C. 



l-iS 



Eesults in 100 parts. 



Ammonia 



Phosphoric acid (? 0O5) 



Limo (CaO) 



Phosphate of ahimiua and iron 



Loss on ignition • • 



Eesiduum, insoluble in hydrochloric acid 



3-03 



8-18 

 23 -5 1 



32-sa 



14-5J: 



We have said that the suspended matters Avere in very small amount in 

 the supernatant A\-ater ; this is evidently merely a question of time allowed for 

 settling. It will be seen that the amount of ammonia in solution is some- 

 what greater in the cfflneiit water than in the sewage, doubtless from the 

 decomposition of some of the soluble organic matter in solution ; but the 

 most remarkable thing is that the organic matter in solution was almost 

 entirely removed in this experiment, so that while the sewage contained 0-90 

 part of organic nitrogen in solution in 100,000 parts, the supernatant water 

 only contained 0-02 part. It must, however, be distinctly understood that; 

 this is only a preliminary experiment, from which general conclusions must 

 not be too hastily drawn. The supernatant water contained a considerable 

 quantity of phosphoric acid, viz. 5-53 parts in 100,000. 



The analysis of the precipitate shows it to contain a largo proportion of 

 phosphate of lime ; and its value is much enhanced by the three per cent, of 

 ammonia which it also contains. 



The ijresence of phosphoric acid in the supernatant water would be of con- 

 siderable advantage if this were afterwards used for irrigation, but, unless 

 means are devised for separating it, would constitute a serious loss if the 

 water were thrown away. 



On the whole, then, this preliminary experiment shows that the process in 

 question well deserves further and careful investigation. 



Sectiok IV. — Additional Note on tJie Dry Earth system. 



In the last Eeport'the Committee gave the results which Dr. Gilbert had 

 obtained from the analysis of soil which had been used in an earth-closet 

 either once or twice. 



It appeared that, " calculated upon the air-dried condition, the increase in 

 the percentage of nitrogen was only about 0-15 each time the soil was used ; 

 and, even after using twice, the soil was not richer than good garden-mould." 



Prom two agreeing determinations Dr. Gilbert now finds that soil which 

 has been used three times in the closet contains, when dried at 100° C, only 

 0-446 per cent, of nitrogen; and dupHcate determinations entirely confirmed 

 this result, so that we have the following series : — 



So that the remark made by the Committee last year with regard to soil 

 which had been used twice, " that such a manure, even if disposed of free of 

 charge, would bear carriage to a very short distance only," is applicable also 

 to soil which has been used three times in the earth-closet. 



