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OCR for page 49
49
NAS/CWTC 0 23 -8 2
Name: SODIUM METABISULFITE, SODIUM PYROSULFATE
CAS No 7631-90-5
· —
Chemical Formula: Na2S2O5
Description:
Formula Weight: 174.1
White to slight yellow crystals with a sulfurous odor.
When in solution, sodium metabisulfite is formed. It has
a Volubility in water of 54 g/100 ml at 20°C and is avail-
able at a commercial strength of 97.5-99.0% sodium meta-
bisulfite.
Use:
Used to remove chlorine and other oxidants
Purity Requirements:
.
The RMIC values are based on a maximum dosage of 15 mg of
sodium metabisulfite/liter of water and are to be com-
pared to impurity concentrations obtained by using sample
procedures described in this monograph. If the actual
dosage is other than 15 mg/liter, the user is cautioned
to consult Table 2 for appropriate RMIC values.
Impurity
Arsenic
Selenium
Bulk Sample Collection:
RMIC mg Impurity/kg
Sodium Metabisulfite
300
70
Sample in accordance with Standard for Sodium Meta-
bisulfite, AWWA B601-77, American Water Works
Association, Denver, Colorado (1977).
OCR for page 50
50
Analytical Sample Preparation:
Weigh out 2.5 g of sodium metabisulfite. In a 150-ml
acid-washed beaker, dissolve the sample in 100 ml of
deionized distilled water. Under a hood, acidify the
solution with concentrated HNO3 to a pH of less than
2. Gently heat the solution to reduce the volume below
100 ml, making certain that it does not boil. Quantita-
tively transfer to a 100-ml acid-washed volumetric flask
and make to volume with deionized distilled water.
Process a reagent blank by the same procedure.
Sample Analyses:
The analyses are to be performed on the sodium meta-
bisulfite sample in accordance with:
Standard Methods for the Examination of Water and Waste-
water, 15th Edition, American Public Health Association,
Washington, D.C. (1981).
Arsenic Section 304
Selenium Section 304
Representative terms from entire chapter:
deionized distilled
