I06 BROOMALL : 



ammonia, free araraotiia, nitrites, nitrates, chlorides, required 

 oxygen and total solids. Other determinations are often 

 made but these in practice are all that are usually needed. 

 Before taking these up in detail, however, a few words in 

 general concerning organic matter and its decomposition may 

 be appropriate. 



Organic matter in a given water is not dangerous of itself, 

 as long before it reaches this intensity the palate rebels 

 against using the water. Its presence is of great importance, 

 however, as indicative of the extent to which the supply is 

 being contaminated. If this contamination were due to veg- 

 etable matter only, it would be of little importance except in 

 so far as it provided a good culture medium for such bacteria 

 as are contained in the water. On the other hand, if this 

 organic matter contains much nitrogenous material, derived 

 as it usually is from animal matter, we must fear sewage or 

 other dangerous contamination. 



In the decomposition of albuminous matter, whether by 

 simple chemical action or as a result of bacterial growth, it is 

 the state or condition of the nitrogen which is most indicative 

 of the stage of the decomposition. The first step in the 

 decomposition is the production of ammonia. This ammonia, 

 as the process goes on, is oxidized into various nitrites, and 

 these, finally, into the ultimate products, the nitrates. When 

 this stage is reached the inorganic matter has become inoffen- 

 sive, as long before this the carbon, hydrogen, oxygen, sul- 

 phur and phosphorus of the albuminous matter have gone off 

 in various gaseous combinations or become combined in 

 stable form. It is the nitrogen, therefore, by reason of the 

 greater importance of this element in the albumin molecule, 

 which is the indicator of the extent of decomposition and 

 oxidation of the organic matter. Let us now return to the 

 chemical determinations referred to above. 



Albuminoid ammonia is the ammonia produced from the 

 actual existing nitrogenous matter in the water by an artifi- 

 cial decomposition. This change, which is more or less sim- 



