MARSHALL O. LEIGHTON 



(B) Consequently, while a low ratio as i to 5 between the nitrogen of the free 

 ammonia and the nitrogen of the albuminoid ammonia indicates pollution, the reverse 

 cannot be said to be a strong indication that the water is a normal water. 



(C) A colorless water containing that amount of nitrogenous matter represented 

 by 0.25 milligram of nitrogen as albuminoid ammonia per liter is looked upon with 

 suspicion. 



(D) Free ammonia always indicates organic matter in the process of decompo- 

 sition. In unpolluted surface waters it is rarely high, being removed almost as 

 fast as formed by vegetable and animal organisms in the water, and an amount of 

 nitrogen as free ammonia above o . 05 milligram per liter is unusual, and, if it does 

 occur, the water cannot be considered as an unpolluted water unless that fact is clearly 

 established by other data. 



Attention is then called to seasonal variations and the increase 

 in free ammonia during the autumn in northern countries. 



(E) Concerning nitrogen as nitrites: 



More than 0.002 milligram per liter is an unfavorable indication. 



(F) Concerning nitrogen as nitrates: 



It is never present in any large amount, seldom exceeding o . i milligram per liter. 

 Higher amounts than this, being unusual, must be looked upon with suspicion. 



Professor Kinnicutt then explains that the above interpretations 

 refer to reservoir, pond, and lake waters, but that in river waters 



high nitrogen as free ammonia, as albuminoid ammonia, and as nitrites charac- 

 teristic of recent pollution in ponds and reservoirs may be due to the decomposition of 

 algae life, which was stimulated by the entrance of sewage in the upper stretches of 

 the river. 



Accepting the above as an authoritative basis of interpretation 

 and it is the one which closely corresponds to that which the writer 

 has found in very general use let us interpret a few analyses. Ref- 

 erence will be made by letter to the foregoing quotations, so that 

 the basis of each interpretation may be clearly denned. 



SERIES "A." 

 PARTS PER MILLION. 



There are presented in the above series three analyses of pond 

 waters. All are practically colorless, and Nos. 2 and 3 have a 



