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OCR for page 36
36 Name: FLUOSILICIC ACID, HYDROFLUOSILICIC ACID CAS No.: 16961-83-4 Chemical Formula: H2SiF~ v Description . NAS/CWIC 015-82 Formula Weight: 88.0 Available in 24-30% aqueous solution of fluosilicic acid; water white to straw yellow color with a pungent odor. Use . Used as source of fluoride. Purity Requirements: Analyses of available grades of fluosilicic acid 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 analyses are desired, the following protocol is recommended. Bulk Sample Collection: Sample in accordance with Standard for Fluosilicic Acid, AWWA B703-71, American Water Works Association, Denver, Colorado (1971). Analytical Sample Preparation . Weigh out 2.5 g of fluosilicic acid. In a 150-ml acid- washed beaker, dissolve the sample with 100 ml of deion- ized distilled water. Under a hood, acidify the solution with concentrated HC1 to a pH of less than 2. Add hydrox- ylamine hydrochloride until the solution turns clear. Gently heat the solution to reduce the volume below 100 ml, making certain that it does not boil. Quantitively

OCR for page 36
37 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 fluosilicic acid 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