January 12, 1906.] 



SCIENCE. 



59 



left on evaporation of such waters afforded 

 trustworthy evidence as to the source of 

 the organic matter. Thus he concluded, 

 that if the ratio was as low as 1 to 3 the 

 organic matter was of animal origin; if as 

 high as 1 to 8 it was chiefly, if not exclu- 

 sively, of vegetable origin, and that if the 

 ratio was between these two proportions 

 the analyst must be guided in his opinion 

 by the amount of inorganic nitrogen the 

 water contained, and by his knowledge of 

 the surroundings of the source of the water. 



This work of Frankland deserves much 

 closer study than it has as yet received. 

 His idea that reliable information regard- 

 ing the source of the organic matter in a 

 water can be obtained from a knowledge of 

 the amount of organic carbon and organic 

 nitrogen is, in my opinion, undoubtedly 

 sound. The reason why this method has 

 not been more generally adopted is un- 

 doubtedly due to the difficulties in correctly 

 determining these two factors by th^ proc- 

 ess used by Frankland, which consisted in 

 measuring the amount of carbon dioxide 

 formed and the amount of nitrogen given 

 off, by the combustion of the residue left 

 on evaporation. If as simple a process 

 for determining the organic carbon as we 

 now have for determining the organic 

 nitrogen could be devised, I believe Frank- 

 land's method for deciding upon the char- 

 acter of a surface water would receive the 

 careful study it certainly deserves. 



The method of determining the character 

 of a water from the ratio that exists be- 

 tween the carbon and nitrogen, being recog- 

 nized as of comparatively little practical 

 worth, on account of the difficulty of de- 

 termining the carbon, attention to-day is 

 concentrated upon the nitrogen content of 

 a water. 



The usual method used for determining 

 the nitrogen in the undeeomposed nitrog- 

 enous compounds is the albuminoid am- 

 monia method of Wanklyn. It gives only 



an approximation of the total amount of 

 nitrogen thus occurring, but taken in con- 

 nection with the free ammonia present it 

 undoubtedly often gives valuable indica- 

 tions as to the source of the nitrogenous 

 compounds. 



In fresh sewage the amount of nitrogen 

 as free ammonia is from three to four times 

 that of the nitrogen in the albuminoid 

 ammonia, and in sewage effluents from 

 twenty to thirty times, while in peaty water 

 or water containing an infusion of leaves 

 the nitrogen in the albuminoid ammonia is 

 from ten to twenty times the nitrogen in 

 free ammonia, hence when a surface water, 

 not including rain or snow water, gives a 

 greater amount of nitrogen as free am- 

 monia than it does as albuminoid ammonia 

 the indications are that the water has cer- 

 tainly been polluted by sewage and that 

 the source of the organic matter is of 

 animal origin, and with a large amount of 

 nitrogen as albuminoid ammonia (over 

 twenty-five hundredths of a milligram per 

 liter), a ratio of the nitrogen of the free 

 ammonia to the nitrogen of the albuminoid 

 ammonia of less than 1 to 5 is suspicious. 



Free ammonia contained in a water may 

 be rapidly removed by plant life or be- 

 changed into nitrites and nitrates, and 

 then be absorbed by algal forms, the^ 

 plant life thus stimulated again adding to 

 the water undeeomposed nitrogenous com- 

 pounds. Consequently, while a low ratio 

 as 1 to 5 between the nitrogen of the free- 

 ammonia and the nitrogen of the albumin- 

 oid ammonia indicates pollution, the re- 

 verse can not be said to be a strong indica- 

 tion that the water is a normal water, one 

 containing only vegetable matter. 



It is a well-established fact that it is not 

 safe to form a judgment of a water from 

 the consideration of any single nitrogen 

 factor, and that unpolluted surface waters 

 are known where the nitrogen, as albu- 

 minoid ammonia, is much larger than in 



