21 



recent years, nor am I aware that it is in use by any Canadian analyst 

 at present. Prof. Marsan, in December, 1888, found 9 parts organic 

 carbon and 0.47 parts nitrogen per million in the Ottawa city supply, 

 and did not consider these numbers to condemn the water for domestic 

 use. 



The ignited residue contains the inorganic salts, sand, etc., which 

 were present in the water. Unless these are in excessive amount their 

 discrimination is not necessary, since in ordinary water samples they 

 consist of lime, magnesium, or soda salts, quite harmless in character, 

 unless, as I have already explained, the water is wanted for boiler 

 supply. Many analyses of the Ottawa river water shew the ignited 

 residue to vary from 20 to about 80 parts per million, according to the 

 season of the year, and the part of the river from which the sample is 

 collected. Other rivers show a much higher inorganic content, as, for 

 instance, the Grand River, at Brantford (Nov., 1889), 348 parts per 

 million, and the Assiniboine, near Winnipeg (May, 1888), which gave 

 1088 parts per million. 



In this residue, however, we always look for phosphoric acid, since 

 phosphates are highly characteristic of sewage, and their presence in the 

 minutest traces is a very suspicious indication. 



7. JVi^ro^en ex\st']ng as ammonia in water is present in consequence 

 of the fact that whenever oiganic matter containing nitrogen undergoes 

 decay a considerable proportion of this nitrogen takes the form of am- 

 monia, and the exceeding solubility of this gas in water causes it to be 

 at once dissolved. You are. many of you at least, acquainted with the 

 fact that the atmosphere of a stable, unless kept very thoroughly cleaned, 

 has a decided smell of spirits ot hartshorn. This odour is due to the 

 decomposing nitrogenous matters present, and the formation of ammo- 

 nia as one of the products of decay. The universal occurrence of organic 

 decay makes it practically impossible that a natural water should be 

 absolutely free from ammonia. When, as in some tables of analysis, 

 you find nitrogen as ammonia stated to be absent, you must understand 

 this to mean that the amount present is too small to make its quanti- 

 tative estimation possible. Yet it is wonderful with what certainty we 

 can measure minute traces of ammonia. When you find tables in which 

 the nitrogen existing as ammonia is stated to three places of decimals, 



