CHEMICAL ANALYSIS 57 



congregate at the mouths of sewers where faecal matter is 

 visibly floating, being attracted by the fragments of food and 

 insects carried down by the sewage. Fish, in fact, are more 

 affected by muddy water and by chemicals from factories than 

 by excreta. Duncan and F. Hoppe Seyler found that perch, 

 trout, etc., could thrive in water holding 3 or 4 c.c. of oxygen 

 in solution per litre, but soon died when only 17 c.c. was 

 present.^ 



Many waters are inoffensive which contain a comparatively 

 high amount of albuminoid ammonia. The following, on the 

 other hand, is an example of a putrescent and otherwise 

 objectionable liquid which did not show a corresponding excess 

 of albuminoid. I diluted a putrid meat solution with water 

 in the proportion of i to 6,000, and the fluid, which smelt 

 strongly like sewage, was analyzed like an ordinary sewage 

 effluent. It gave in parts per 100,000 — free NH3, 0*025 

 albuminoid NH3, 0*083; oxygen consumed, 0*044; ^^ nitrite 

 or nitrate. This liquid remained putrid and foul-smelling for 

 more than a week. Dr. Kenwood experienced " that the 

 albuminoid ammonia in offensive effluents was initially materially 

 below that of several of the inoffensive effluents."'^ 



It is obvious, therefore, that an arbitrary standard based 

 upon the albuminoid figure is valueless. 



The processes at work in destroying putrescible matter in 

 sewage involve its transition into products yielding albuminoid 

 and free ammonia ; an increase in the free ammonia, therefore, 

 is actually a proof that so much destruction of nitrogenous 

 organic matter has occurred. Albuminoid ammonia in an 

 effluent may also be a good sign, indicating either that organic 

 matter as sediment has gone into solution, or that stable soluble 

 matter has been partially broken up.^ 



In 1893 I showed that different kinds of " albuminoid 

 ammonia " are possible, since waters containing fresh sewage 

 which has been partly oxidized by sodium peroxide yield the 

 remainder of their ammonia to alkaline permanganate much 

 more rapidly than when the water has not been so treated. 

 This suggests the presence in waters of organic nitrogenous 

 matters which, when partially oxidized, are then in a condition 

 to be completely broken up by the stronger reagent. When 



^ ZcH. fhysioL Chemie, xvii., 165. 



2 Journal of the Royal Sanitary Institute, vol. xxii., part ii., p. 108. 



^ Rideal, British Association Reports, 1893. 



