YSI 9300 Photometer - Manual (Page 101)

Test Procedure
1 Filter sample if necessary to obtain a clear solution.
2 Fill the test tube with sample to the 10 ml mark.
3 Add one Sulfitest No 1 tablet, crush and mix to dissolve.
4 Add one Sulfitest No 2 tablet, crush and mix to dissolve. Cap tube immediately.
5 Stand for two minutes to allow full color reduction to take place.
6 Select Phot 34 on the photometer.
7 Take photometer reading in the usual manner (see photometer instructions).
8 The result is displayed as mg/l Na
2
SO
3
.
NOTE
Equipment should be washed immediately after use, with a detergent if necessary, to
prevent staining.
Sulfite concentrations may be expressed as mg/l SO
3
. To convert from mg/l Na
2
SO
3
to mg/l SO
3
multiply by 0.63.
INTERFERENCES
This test is not affected by the presence of other reducing species such as nitrite
(up to 200 mg/l) ferrous iron (up to 20 mg/l) and sulfide (up to 10 mg/l); or by
the presence of polyacrylates.
Chlorine up to 250 mg/l does not cause interference. However, since sulfite and
chlorine do not normally co-exist, the test will not usually be carried out in the
presence of chlorine.
Note: the test gives low results if used in the presence of tannic acid or tannin
treated waters.
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