20 PUBLIC HEALTH CHEMISTRY 



grammes of ammonia, which diluted into 900,000 litres or 

 200,000 gallons of water, would still have caused an appreci- 

 able rise on the amount (if any) of ammonia already present. 

 This illustrates the delicacy of some of these tests. 



Various other estimations are carried out, such as, to 

 determine the presence or absence of poisonous metals, 

 the degree of hardness, etc. These are usefully sum- 

 marized thus : 



Water Analysis. 



This consists of three parts : 



1. Physical examination. 



2. Chemical examination. 



3. Bacteriological examination. 



Physical Examination 

 Transparency clear and bright turbid. 

 Suspended matter stand for twenty-four hours in 

 glass with conical bottom. 

 Colour two-foot tube. 



Taste uncertain iron detectable in I gr. per gallon 

 NaCl in 75 grains per gallon. 

 Smell. 

 Microscopic characters of sediment 



Particles of animal, vegetable, and mineral origin. 



Micro-organisms, bacterial and protozoal. 



Chemical Examination. 

 Reaction. 



Dissolved solids Total. 

 Fixed. 

 Volatile. 



Charring on ignition fumes odour. 

 Chlorine. 



Poisonous metals Pb, Cu, Fe, Zn, As, Sn. 

 Lime and magnesia. 

 Phosphates and sulphates. 



Free carbonic acid bicarbonates carbonates ; dissolved 

 oxygen ; sulphuretted hydrogen. 

 Hardness Total. 



Permanent. 

 Temporary. 



