Click for next page ( 16


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 15
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.

OCR for page 15
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

OCR for page 15
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