LaMotte AM-21 Water Pollution Detection Outfit - Manual (Page 19)

Chloride Test (also see Salinity Test)
Chloride is one of the major anions to be found in water and sewage. Its
presence in large amounts may be due to natural processes such as the
passage of water through natural salt formations in the earth or it may be an
indicator of pollution from sea water or industrial and domestic wastes. Any
change from the normal chloride content of a natural water should be reason
for suspecting pollution from one of these sources. US Public Health Service
Drinking Water Standards recommend a maximum chloride content of 250
ppm as chloride.
Chloride is determined by titrating the sample with a silver nitrate solution
using potassium chromate as the endpoint indicator.
The same test reagents are used in both the Chloride and the Salinity
determinations. The chloride test is run on an undiluted sample. The salinity
test is run on a sample that has been diluted with chloride-free water.
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