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OCR for page 34
34 Name: FERROUS SULFATE CAS No.: 7720-78-7 Chemical Formula: Description: FeSO4 . 7H2O NAS/CWTC 014-82 Formula Weight: 277.9 Pale, bluish-green crystals or granules. Ferrous salts tend to oxidize in moist air and form brownish-colored ferric salts. A 10% solution will have a pH of approxi- mately 3.7. It is soluble in water and insoluble in alcohol. Use: Used in coagulation. Purity Requirements: The RMIC values are based on a maximum dosage of 80 mg of ferrous sulfate*/liter of water and are to be compared to impurity concentrations obtained by using sample proce- dures described in this monograph. If the actual dosage is other than 80 mg/liter, the user is cautioned to consult Table 2 for appropriate RMIC values. RMIC mg Impurity/kg Ferrous Sulfate Impurity Arsenic Cadmium Chromium Lead Mercury Selenium Silver *Calculated on basis of FeSO4 7H2O. 60 10 60 60 3 10 60

OCR for page 34
35 Bulk Sample Collection: Sample in accordance with Standard for Ferrous Sulfate, AWWA B402-68, American Water Works Association, Denver, Colorado (1968). Analytical Sample Preparation: In preparing samples, use acid-washed glassware and make all dilutions with deionized distilled water. Weigh 0.8 g of ferrous sulfate (dry weight basis), dissolve, and make up to 1 liter in a volumetric flask. Transfer the solution to a 1.5-liter beaker, add 1 N of 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 equivalent) with vacuum. Quantitatively transfer fil- trate into a beaker, adjust to pH 2 or less with concen- trated 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 ferrous 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