Io8 BROOMAI.I. : 



ammonias in thai the oxidation of the vegetable matter is 

 likewise included. 



The total solids are found by evaporation to dryness and 

 weighing. If the residue is ignited and then re-weighed, the 

 difference gives the amount of organic matter present (plus, 

 however, some chloride driven oflT by the heat.) This organic 

 matter includes both animal and vegetable contamination 

 and therefore corresponds in a measure to the determination 

 of refjuired oxygen. 



As before stated, the impurities indicated liy the al)ove 

 tests, being present in such small amounts as to be measured 

 only in parts per million, can produce absolutely no harmful 

 effect of themselves. They are simply indicators of present 

 or past organic pollution. P'rom them, however, it is impos- 

 sible to determine the actual amount of organic matter that 

 exists or existed in the water on account of the exceedingly 

 complex and variable composition of such matter. The best 

 that can be done is to measure the decomposition products, 

 either natural or artificial, of such organic matter, and deter- 

 mine by comparison with other good water supplies whether 

 they are within safe limits. An idea of the magnitude of the 

 quantities concerned may be obtained from the table below, 

 given by Dr. A. R. Leeds as a standard for American rivers 

 used for water supply purposes : — 



Albuminoifl Ammonia lo to .28 parts per million 



Free Ammonia 01 to .12 



Nitrogen as Nitrites .003 



Nitrogen as Nitrates i.ii to 3.S9 " " 



Chlorine as Chlorides 3.00 lo 10.00 " " 



Oxygen Consuming Capacity. . 5.00 lo 7.00 " 



Much information can be obtained from a careful study of 

 the actual and relative values of the various determinations. 

 If the albuminoid ammonia is relatively very high, it indi- 

 cates that the source of organic pollution of the water is so 

 close at hand that decomposition has scarcely had time to 



