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15 Name: CALCIUM HYDROXIDE, SLAKED LIME CAS No.: 1305-62-0 Chemical Formula: Ca(OH)2 Description: NAS/CWTC 005-82 Formula Weight: 74.0 A white, dry fine powder, free from lumps, possessing an alkaline, slightly bitter taste. Solubility in water: 1 g/630 ml at 25C, 1 g/1,300 ml at 100C. Soluble in glycerin but insoluble in alcohol. Use: Used primarily as a softening agent and for pH adjustment. Purity Requirements: The RMIC values are based on a maximum dosage of 650 mg of calcium hydroxide/liter of water and are to be com- pared to impurity concentrations obtained by using sample procedures described in this monograph. If the actual dosage is other than 650 mg/liter, the user is cautioned to consult Table 2 for appropriate RMIC values. Impurity Arsenic Cadmium Chromium Fluoride Lead Selenium Silver RMIC mg Impurity/kg Calcium Hydroxide 10 2 10 * 10 10 *A RMIC has not been established for fluoride. All producers of calcium hydroxide must analyze and state in the certified analysis the concentration of fluoride in the calcium hydroxide produced.

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16 Bulk Sample Collection: Sample in accordance with Standard for Lime, AWWA B202-77, American Water Works Association, Denver, Colorado (1977), except store final 2-lb sample in moistureproof glass. Analytical Sample Preparation: Take a 66.7-g portion of the sample and pulverize using a nonmetallic pulverizer or a glass mortar and pestle until sample passes a No. 100 U.S. standard sieve. Mix pulver- ized sample thoroughly and place in an airtight moisture- proof glass container. Pippette 4 ml of deionized dis- tilled water in a 150-ml beaker. Place on a 60C hot plate. Place stirring rod in beaker and add 1.33 g of pulverized calcium hydroxide slowly while stirring. Mix paste thoroughly to include all pulverized sample. When a smooth paste is obtained, remove beaker from hot plate and slowly add 50 ml of 80C deionized distilled water while stirring. Cool to room temperature. Filter through GF/C filter under vacuum into a 150-ml beaker. Using a 25-ml burette, add 1+4 HACK until the pH remains between 1.8 and 2.0 for 5 minutes. Transfer quantita- tively into a 1,000-ml volumetric flask and dilute to volume with nitric acid dilution solution. Analytical Sample Preparation--Fluoride: Weigh 10 g of sample (to the nearest milligram) into a 400-ml beaker. Rehydrate the lime by slowly and care- fully adding up to 250 ml of deionized water. Place 400 ml of deionized distilled water into a 1-liter side-arm distilling flask. Carefully add 200 ml of concentrated sulfuric acid. Swirl until contents are homogeneous (essential for safety during distillation). Add 25-35 glass boiling beads. Begin heating, slowly at first, until the temperature reaches 180C. Discard the dis- tillate. Cool the acid mixture. Carefully, quantita- tively transfer the lime suspension to the distilling flask until all the slurry has been transferred along with 300 + 5 ml of water (i.e., sample contained in 300 m_ of water). If there is reason to suspect presence of chlorides in sample, add 5 mg of silver sulfate for every

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17 milligram of chloride. Distill until flask temperature again reaches 180C. Determine fluoride in the distil- late. Sample Analyses: The analyses are to be performed on the calcium hydroxide 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 Fluoride Selenium Silver Section 304 Section 304 Section 413B Section 304 Section 304