PROCEEDINGS OF THE COTTESVVOLD CLUB I25 



(3) The Chlorides. Urine contains chloride of sodium 

 and a large quantity of chloride in the water, taken 

 with other circumstances may be indicative of 

 sewage. 



(4) Nitrates. The presence of nitrate in water is indi- 

 cative of matter that has at some time near or far 

 existed in the form of nitrogeneous organic matter. 

 A large quantity of nitrate is often found in shallow 

 wells, and affords evidence of the existence, or pre- 

 vious existence, of decomposing organic matter 

 situated at no great distance from the well. 



(5) Nitrites. The existence of any considerable quantity 

 of nitrite is reliable evidence of recent pollution, 

 nitrite being an intermediate product in the reduction 

 of organic material. 



(6) Free or Sahne Ammonia, which is a first product 

 of the decomposition of nitrogeneous material such as 

 is contained in sewage. 



(7) Albuminoid or organic ammonia, which is ammonia 

 formed in the process of analysis from the nitrogeneous 

 organic compounds of varied composition contained 

 in the water, and gives a relative measurement of the 

 quantity of such compounds present. 



(8) The amount of oxygen absorbed by the water from 

 an acid solution of permanganate of potash. The 

 oxygen is absorbed to oxidize organic matter present 

 and of such readily oxidizable matter the process is a 

 measure. It is indicative rather of carbonaceous 

 than of nitrogeneous compounds, and taken together 

 with the albuminoid ammonia found, enables the 

 analyst to determine whether the organic matter pre- 

 sent be of vegetable or of animal origin. 



(9) The amount of oxygen dissolved in the water. This 

 estimation is sometimes made and indicates the 

 activity of the oxidation of organic material in the 

 water that is going on as a result of bacterial growth. 



