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OCR for page 32
32 Name: FERRIC SULFATE CAS No.: 10028-22-5 Chemical Formula: Description: Fe2(SO4)3 ' nH2O NAS/CWTC 013-82 Formula Weight: 399.8 Solid is red-gray to red-brown granules containing four to five waters of hydration. Usually used in solutions of 30-50% by weight ferric sulfate. Solutions are reddish-brown. Use: Used in coagulation. Purity Requirements: The RMIC values are based on a maximum dosage of 100 mg of ferric sulfate/liter of water and are to be compared to impurity concentrations obtained by using sample procedures described in this monograph. If the actual dosage is other than 100 mg/liter, the user is cautioned to consult Table 2 for appropriate RMIC values. Impurity Arsenic Cadmium Chromium Lead Mercury Selenium Silver RMIC mg Impurity/kg Ferric Sulfate 50 10 50 50 2 10 50

OCR for page 32
33 Bulk Sample Collection: Sample in accordance with Standard for Ferric Sulfate, AWWA B406-64, American Water Works Association, Denver, Colorado (1964). Analytical Sample Preparation: In preparing samples, use acid-washed glassware and make all dilutions with deionized distilled water. Weigh 1 g of ferric sulfate (dry weight basis), dissolve, and make up to 1 liter in a volumetric flask. Transfer the solu- tion to a 1.5-liter beaker, add 1 N NaOH dropwise with constant stirring to adjust to pH 6. Mix well, let stand for 1 hour, and filter through a GF/C filter (or equiva- lent) with vacuum. Quantitatively transfer filtrate into a beaker, adjust to pH 2 or less with concentrated HNO3, and evaporate on a hot plate, without boiling, to reduce the volume to less than 1 liter. Cool, quantitatively transfer to a 1-liter volumetric flask, and make up to volume. Similarly treat a reagent blank. Sample Analyses: The analyses are to be performed on the ferric sulfate solution in accordance with: Standard Methods for the Examination of Water and Waste- water, 15th edition, American Public Health Association, Washington, D.C. (1981). Arsenic Cadmium Chromium Lead Mercury Selenium Silver Section 304 Section 304 Section 304 Section 304 Section 303F Section 304 Section 304