36 SEWAGE AND ITS PURIFICATION 



Free and Albuminoid Ammonia by Distillation. 



The apparatus must first be freed from ammonia by distilling 

 water through it till the distillate shows no reaction with 

 Nessler's test. Then 500 c.c. of pure water, or of good tap water 

 in which the free and albuminoid ammonia are known, are 

 placed in the retort, and 100 c.c. (or a less quantity according to 

 the strength) of the sewage added. The distillation is then 

 carried on till free ammonia ceases to come over except in 

 traces, which will generally happen when 200 c.c. have been 

 collected. Fifty c.c. of alkaline permanganate solution are 

 next added, and three pieces of ignited pumice, and the distilla- 

 tion is continued until another 200 c.c. have been collected. 

 Suitable fractions of the two distillates are then diluted with 

 ammonia-free water to 50 c.c. and Nesslerized, the first result 

 being put down as free ammonia, the latter as albuminoid. 

 The ammonia is preferably calculated to nitrogen, as mentioned 

 in the British Association Report. In the case of acid trade 

 effluents, ignited carbonate of soda, in slight excess, must be 

 added before the first distillation. 



In distilling sewage there is no exact point when the *' free 

 ammonia " ceases to come over, on account of the gradual 

 decomposition of various nitrogenous matters by heat. Phelps 

 distilled the following pure substances with water and a little 

 sodium carbonate, and the percentage of the total nitrogen 

 coming over as free ammonia was : Urea, 2 ; gelatin, i'4 ; 

 casein, o*68 ; egg albumin, 3*2 ; Witte's peptone, i'4 ; naphthyl- 

 amine, o'l.^ These proportions are small, though they are 

 lower than would be yielded by some of the intermediate 

 products of decomposition, and they depend upon concentra- 

 tion and on the duration of heating. Wanklyn showed, in 

 1867, that with urea in prolonged boiling there was a very slow 

 evolution of ammonia, and the greater part was finally decom- 

 posed. Phelps found (loc. cit.), as the average of fifty analyses 

 of sewage, that the excess of " free ammonia " by distillation 

 over that by direct titration was 13*2 per cent, of the latter. 



The action of the alkaline permanganate is also not definite ; 

 therefore it is necessary to proceed in a defined manner to 

 obtain comparative results. For some time I determined the 

 " total ammonia " by adding to the dilute sewage alkaline per- 



1 American Public Health Association, Journal of Infectious Diseases, Chicago, 

 March 19, 1904. 



