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53
NAS/CWTC 025-82
Name: SODIUM SILICOFLUORIDE, SODIUM FLUOSILICATE
CAS No.: 16893-85-9
Chemical Formula: Na2SiF6
Description:
Formula Weight: 132
White, yellowish-white, or Nile blue crystalline powder,
odorless, acidic taste, and hydroscopic.
Use:
Used as source of fluoride.
Purity Requirements:
Analyses of available grades of sodium silicofluoride
show the presence of arsenic and lead but at levels far
below that which would necessitate RMIC values based on a
maximum dosage of 1.2 mg of fluoride ion/liter. If anal-
yses are desired, the following protocol is recommended.
Bulk Sample Collection:
Sample in accordance with Standard for Sodium Silico-
fluoride, AWWA B702-74, American Water Works Association,
Denver, Colorado (1974).
Analytical Sample Preparation
Weigh out 2.5 g of sodium silicofluoride. In a 150-ml
acid-washed beaker, dissolve the sample with 100 ml of
deionized distilled water. Under a hood, acidify the
solution with concentrated EC1 to a pH of less than 2.
Add hydroxylamine hydrochloride until the solution turns
clear. Gently heat the solution to reduce the volume
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below 100 ml, making certain that it does not boil. Quan-
titively transfer to a 100-ml acid-washed volumetric flask
and make to volume with deionized distilled water. Pro-
cess a reagent blank by the same procedure.
Sample Analyses:
The analyses are to be performed on the sodium silico-
fluoride 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
Lead
Section 304
Section 304
Representative terms from entire chapter:
distilled water
