2IO Water Analysis [353 



for certain technical purposes this determination is of consider- 

 able importance. When water is required for the purpose of 

 raising steam, the greater the quantity of solid matter the greater 

 the quantity of ' boiler scale ' that will be produced. Again, 

 in many manufactures where soap is used it is important that 

 the water be as free as possible from solid matter. On the 

 other hand, for brewing it is necessary that the water contain 

 a certain quantity of sulphate of lime. 



Ammonium Salts. These are represented by the free 

 ammonia, and are almost always of animal origin. Seeing that 

 ammonia is one of the first products of the decomposition of 

 animal matter, the presence of large quantities of ammonia in 

 water points to the fact that it has been recently contaminated 

 with sewage in some form or other. It must be remembered, 

 however, that the ammonium salts are not in themselves 

 injurious, and that their presence in a water does not render it 

 unfit for drinking purposes. It rather puts us on our guard, 

 and directs us to look for other more harmful substances. 



Free Ammonia may be present in quantities varying from 

 •0005 grain per gallon, or even less in spring waters, to 2 grains 

 per gallon in shallow well waters. Sewage may contain 8 grains 

 per gallon. 



As a rule, water should contain less than -oi grain per 

 gallon. 



Albuminoid Ammonia. This is the substance which, more 

 than all others, should be absent from drinking water, as it is 

 generally due to unchanged sewage. It should never exceed 

 '008 grain per gallon. 



Oxidisable Matter. This, again, is an indication of the 

 organic impurities in water, not necessarily, however, of animal 

 origin. In upland surface waters the oxygen absorbed should 

 not exceed *3 grain per gallon. In other waters it should not 

 exceed '14 grain per gallon. 



