LaMotte AM-21 Water Pollution Detection Outfit - Manual (Page 41)

Salinity Test (also see Chlorides)
The extent of contamination of a fresh water supply in areas adjacent to salt
water sources can be easily detected by a determination of its salinity.
Salinity, in this case, is a term used to describe the total solids content of sea
water and has a different meaning than the term as used to describe the
solids content of fresh water used for agricultural purposes. Because of the
relatively constant chemical balance of sea water, its salinity can be
determined by a measure of its total halide content, which is principally in
the form of chlorides.
The salinity of a water can be completely removed by distillation or
demineralization by ion exchange resins. Also, practical use has been made
of special ion exchange membrane systems for reducing the salt content to
within limits permissible for potable purposes.
The chemical test for salinity involves titration of the test sample with silver
nitrate using potassium chromate as the 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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