1866.] with the supply of water to Calcutta. 231 



be satisfactory, and that was to determine the amount of nitrogen 

 existing in other forms than those of ammonia and nitric acid, this 

 being the only way in which the amount of undecomposed or 

 imperfectly decomposed animal matter can be estimated. The way in 

 which this is usually done is by what is well known to chemists as the 

 soda lime process, and depends on the circumstance that all such 

 animal substances containing nitrogen (this not including nitric acid 

 however), when heated to redness in contact with a hvdrated alkali, 

 yield up all their nitrogen combined with hydrogen as ammonia, and 

 this ammonia can by suitable arrangement be collected and its amount 

 ascertained. I am not aware that this plan has been much applied 

 to the examination of animal matter in waters, no doubt on account of 

 the minute quantity of nitrogen present ; nevertheless it appeared to me 

 that it might be modified so as to estimate it even in drinking water. 

 I intended to have postponed the trial of this process altogether, as I 

 had not time to make proper arrangements and test the accuracy of the 

 plan. However I made three experiments in a rather hasty and 

 crude manner with such means as I had at hand. They are not at all 

 to be depended on, but I may give the results as obtained. 



River water of 2nd June, Ebb, from Chandernagore, containing very 

 little tidal water. 100,000 grains gave .028 grains ammonia. 



River water of 21st August, Ebb, from Barnagore. 100,000 grains 

 gave .030 grains ammonia. 



River water of May and June, Flood tide, from Barnagore. 100,000 

 grains gave .010 grains ammonia. 



The results, as I have already said, are not to be depended on. Yet 

 it cannot be denied that they are in accordance with the results 

 obtained in other ways, respecting the organic matter. The ready 

 formed ammonia existing in the water had of course been previously 

 removed. 



In a practical point of view this portion of the subject is of the 

 principal importance, as more than any other it bears on the question 

 as to how far the river water is contaminated by the sewage oi 

 Calcutta. Judging from the results obtained and just mentioned 

 respecting ammonia and fixed nitrogenous organic matter, the amount. 

 is not great : even at the highest tide at flood on the 14th June of 

 this year, after twelve months of an unusually small amount of rain- 



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