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OCR for page 55
55 Name: SULFUR DIOXIDE CAS No.: 7446-09-5 Chemical Formula SO2 Description: NAS/CWTC 026-82 Formula Weight: 64.0 A colorless gas that liquifies under pressure to form a colorless liquid. As a gas it is corrosive and has a suffocating, pungent odor. When in solution, H2SO3 is formed. It has a solubility in water of 11.3 g/100 ml at 20C and is available at a commercial strength of 100% sulfur dioxide. Use: Used to remove chlorine and other oxidants from water. Purity Requirements: The RMIC values are based on a maximum dosage of 10 mg of sulfur dioxide/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 10 mg/liter, the user is cautioned to consult Table 2 for appropriate RMIC values. Impurity Arsenic Selenium Bulk Sample Collection: RMIC mg Impurity/kg Sulfur Dioxide 500 100 A 300-ml sample of sulfur dioxide injection water should be collected at the point of application. A 300-ml sample of the injection water prior to sulfur dioxide

OCR for page 55
56 addition should also be collected and used for a sample blank. The latter sample should be preserved with 1 ml of concentrated HNO3. Analytical Sample Preparation: Pour 100 ml of sulfur dioxide injection water sample into a 150-ml acid-washed beaker. Determine if the sample has a pH of less than 2. If it does not, acidify the sample with concentrated HNO3 to a pH of less than 2. Transfer to a 100-ml acid-washed volumetric flask. Repeat this preparation procedure with 100 ml of the sample blank. For the mercury analysis, use a separate 100-ml aliquot of sulfur dioxide injection water and sample blank. Repeat the same preparation. Sample Analyses: The analyses are to be performed on the sulfur dioxide 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 Selenium Section 304 Section 304