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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 25°C, 1 g/1,300 ml at 100°C. 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 16
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 60°C 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 80°C 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 180°C. 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 17
17
milligram of chloride. Distill until flask temperature
again reaches 180°C. 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
Representative terms from entire chapter:
distilled water
