YSI 9300 Photometer - Manual (Page 96)

PHOTOMETER TEST INSTRUCTIONS
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Sulfates occur naturally in many waters. Sulfates are introduced into treated
waters by the use of such chemicals as aluminium sulphate, sodium bisulphate
(dry acid) and sulphuric acid. The presence of high levels of sulphate can be
undesirable for a number of reasons.
In industrial waters containing sulfate localised corrosion of iron, steel and
aluminum in plant and pipe work can occur through the action of sulfate-reducing
bacteria. These bacteria, which generate sulphides, cause a characteristic pitting of
the metal surface.
High sulfate levels can also cause damage to concrete and cement based materials
through the formation of calcium sulfhoaluminate. This causes expansion and
crumbling of the cement. It can affect concrete structures and pipes in water
distribution systems carrying sulphate-bearing ground waters; and can attack
grouting in tiled swimming pools using sodium bisulphate for pH adjustment.
The YSI Sulfate test provides a simple method of measuring sulfates over the
range 0 - 200 mg/l SO
4
. Higher levels may be determined by diluting the sample.
Method
The YSI Sulfate test is based on a single tablet reagent containing barium
chloride in a slightly acidic formulation. Barium salts react with sulphates to
form insoluble barium sulphate. At the sulfate levels encountered in the test,
this is observed as turbidity in the test sample. The degree of turbidity is
proportional to the sulfate concentration and is measured using a YSI
Photometer.
Photometer Method
AUTOMATIC
WAVELENGTH
SELECTION
0 – 200 mg/l
PHOT.32.AUTO