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OCR for page 20
20
Name: CALCIUM OXIDE (LIME, QUICKLIME)
CAS No.: 1305-78-8
Chemical Formula CaO
—
Description:
NAS/CWTC 007-82
Formula Weight: 56.0
Hard, white or grayish-white porous pebble or powder,
odorless, and quick slaking. Solubility in water: 1
g/840 ml at 25°C, 1 g/1,740 ml at 100°C. Soluble in
glycerin, but insoluble in alcohol.
Used primarily as a softening agent and for pH adjust-
ments.
Purity Requirements:
The RMIC values are based on a maximum dosage of 500 mg
of calcium oxide/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 500 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 Oxide
10
2
10
*
10
10
*A RMIC has not been established for fluoride. All
producers of calcium oxide must analyze and state the
concentration of fluoride in the calcium oxide produced.
OCR for page 21
21
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:
Crush about half of the 2-lb sample so that it passes a
No. 6 U.S. standard sieve, preferably using a nonmetallic
crusher or a glass mortar and pestle. Mix crushed sample
thoroughly and place in an airtight moistureproof glass
container. Take a 50-g portion of the crushed sample and
pulverize using a nonmetallic pulverizer or a glass mortar
and pestle until sample passes a No. 100 U.S. standard
sieve. Mix pulverized sample thoroughly and place in an
airtight moistureproof glass container.
Initial Slaking:
Pipette 4 ml of deionized distilled water in a 150-ml
beaker. Place on a hot plate at a low heat and bring
water to approximately 60°C. Place stirring rod in
beaker and add 1 g pulverized calcium oxide slowly while
stirring. If necessary, remove beaker from hot plate
momentarily to control spattering. Mix slurry thoroughly
to include all the pulverized lime. 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 HNO3 until the pH remains between 1.8 and 2.0
for 5 minutes. Transfer quantitatively 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
OCR for page 22
22
(essential for safety during distillation). Add 25-35
glass boiling beads. Begin heating, slowly at first,
until the temperature of the flask contents reaches 180°C.
Discard the distillate. Cool the acid mixture. Quantita-
tively transfer the lime suspension (carefully) to the
distilling flask until all the slurry has been transferred
along with 300 + 5 ml of water (i.e., sample contained in
300 ml of water). If there is reason to suspect presence
of chlorides in sample, add 5 mg of silver sulfate for
every milligram of chloride. Distill until flask tempera-
ture again reaches 180°C. Determine fluoride in the
distillate.
Sample Analyses:
The analyses are to be performed on the calcium oxide
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
Fluoride
Lead
Selenium
Silver
304
304
304
413B
304
304
304
Representative terms from entire chapter:
moistureproof glass
