WATER ANALYSIS 



39 



water, the ratio varies from 6 to 12 ; in surface water from 

 cultivated lands, from 4 to 10 ; in shallow wells, from 2 to 

 8 ; in deep wells, and springs, from 2 to 6 ; in sea water it 

 averages about 1-7 ; and in sewage it varies from i to 3, 

 averaging about 2. 



TABLE. 



In waters subjected to oxidation, the ratio tends to 

 be reduced when the organic matter is mainly vegetable, 

 and the reverse when it is animal. Loch Katrine 

 water (average of five years) gave Organic C, 0-148 part 

 per 100,000, and Organic N, 0-016 part per 100,000, and 

 the ratio as 9-2. This method is for trained chemists only. 



Wanklyn, Chapman, and Hall's Method recognizes that 

 organic matter tends to resolve itself into simpler substances, 

 and chooses to estimate the amount of ammonia present, 

 free in solution or as salts, as an index of the amount of 

 organic matter so resolved. Further, the water is so 

 treated subsequently that any organic matter remaining 

 undecomposed has its nitrogen split off as ammonia ; 

 this is measured and furnishes an index of the amount of 

 such organic matter. The absolute amounts of these two 

 ammonias (the first called " the free and saline," the 

 second "the albuminoid ammonia"), and their relative 

 amounts, give valuable evidence of the state of a water 

 with regard to organic pollution. 



Forschammer Process, as modified by Tidy, is commonly 

 called Tidy's Process, and consists in measuring the oxygen- 

 consuming or absorbing power of a water, and inferring 

 therefrom the amount of organic matter present. It has 

 many limitations, but under proper conditions furnishes 

 another item on which to found an estimate of a water. 



