ASTM D1844-86(1999)

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Designation: D 1844 – 86 (Reapproved 1999)
Standard Test Methods for
Chemical Analysis of Basic Lead Silicochromate
This standard is issued under the fixed designation D 1844; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 1648 Specification for Basic Lead Silicochromate Pig-
ment
1.1 These test methods cover the chemical analysis of the
D 2371 Test Method for Pigment Content of Solvent-
pigment commercially known as basic lead silicochromate and
Reducible Paints
are applicable to pigment supplied by the manufacturer and to
pigment, but not mixed pigments, separated from liquid
3. Significance and Use
coatings. The presence of basic lead silicochromate species
3.1 These test methods may be used to confirm the stated
shall be confirmed by X-ray diffraction analysis (see Specifi-
lead oxide, chromium trioxide and silica content of basic lead
cation D 1648).
silicochromate and is useful for quality control.
1.2 For liquid coatings the pigment must first be separated
from the vehicle before conducting the analysis.
4. Purity of Reagents
1.3 The analytical procedures appear in the following order:
4.1 Reagent grade chemicals shall be used in all tests.
Sections
Unless otherwise indicated, it is intended that all reagents shall
Lead oxide 6 to 14
conform to the specifications of the Committee on Analytical
Chromium trioxide 15 to 23
Reagents of the American Chemical Society, where such
Silica 24 to 27
specifications are available. Other grades may be used, pro-
Moisture and other volatile matter 28
Coarse particles 29
vided it is first ascertained that the reagent is of sufficiently
Oil absorption 30
high purity to permit its use without lessening the accuracy of
Mass color and tinting strength 31
the determination.
1.4 This standard does not purport to address the safety
4.2 Unless otherwise indicated, references to water shall be
concerns, if any, associated with its use. It is the responsibility
understood to mean reagent water conforming to Type II of
of the user of this standard to establish appropriate safety and
Specification D 1193.
health practices and determine the applicability of regulatory
5. Preparation of Sample
limitations prior to use.
5.1 Thoroughly mix liquid coatings and separate in accor-
2. Referenced Documents
dance with Test Method D 2371 sufficient pigment to enable
2.1 ASTM Standards:
the required analyses to be carried out.
D 185 Test Methods for Coarse Particles in Pigments,
5.2 Thoroughly mix pigment supplied as such and grind
Pastes, and Paints
separated pigment to a fine powder in a mortar and pestle
D 280 Test Methods for Hygroscopic Moisture (and Other
before taking portions for analysis.
Matter Volatile Under the Test Conditions) in Pigments
TOTAL LEAD AS LEAD OXIDE-GRAVIMETRIC
D 281 Test Method for Oil Absorption of Pigments by
METHOD
Spatula Rub-Out
D 387 Test Method for Color and Strength of Color Pig-
3 6. Apparatus
ments with a Mechanical Muller
6.1 Glass Filtering Crucible (medium-porosity fritted
D 1193 Specification for Reagent Water
disk), dried to constant weight before use.
These test methods are under the jurisdiction of ASTM Committee D-1 on Paint
and Related Coatings, Materials, and Applications and are the direct responsibility
of Subcommittee D01.31 on Pigments Specifications. Reagent Chemicals, American Chemical Society Specifications, American
Current edition approved April 25, 1986. Published June 1986. Originally Chemical Society, Washington, DC. For suggestions on the testing of reagents not
published as D 1844 – 61 T. Last previous edition D 1844 – 78. listed by the American Chemical Society, see Analar Standards for Laboratory
Annual Book of ASTM Standards, Vol 06.03. Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Annual Book of ASTM Standards, Vol 06.01. and National Formulary, U.S. Pharmacopeial Convention, Inc., (USPC), Rockville,
Annual Book of ASTM Standards, Vol 11.01. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 1844
6.2 Platinum Dish. through a glass filtering crucible (medium-porosity fritted
disk), wash three times with hot water, and finally once with
7. Reagents
alcohol. Dry in an oven at 105°C for 2 h, cool, and weigh.
7.1 Acetic Acid (Glacial).
9. Calculation
7.2 Ammonium Hydroxide (sp gr 0.90)—Concentrated am-
monium hydroxide (NH OH).
9.1 Calculate the percent of total lead as lead oxide (PbO) as
7.3 Ammonium Acetate, Acid Solution— To 300 mL of
follows:
water add an equal volume of NH OH. Neutralize with glacial
PbO, % 5 ~P3 69.06!/S
acetic acid and add 20 mL in excess.
7.4 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro- where:
P 5 lead chromate (PbCrO ) precipitate, g,
chloric acid (HCl).
S 5 sample used, g, and
7.5 Hydrofluoric Acid (47 %)—Concentrated hydrofluoric
acid (HF).
molecular weight ~PbO!
7.6 Hydrogen Sulfide (H S)—Handle and use H S in hood.
molecular weight ~PbCrO
2 2
7.7 Isopropyl Alcohol (50 and 98 %). 223.21
5 0.6906 3 100 ~for percent!5 69.06
323.21
7.8 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
(HNO ) (see 7.4.1).
3 69.06 represents the gravimetric factor to convert grams of
7.9 Potassium Dichromate Solution (saturated)—Prepare a
PbCrO to grams of PbO.
saturated solution of potassium dichromate (K Cr O ) in water.
2 2 7 This gravimetric factor has led to high results due to the
7.10 Sulfuric Acid (1 + 1)—Carefully mix 1 volume of
presence of mixed lead chromates and an empirical factor can
concentrated sulfuric acid (H SO , sp gr 1.84) with 1 volume
2 4 be used to compensate:
of water (see 7.4.1).
Empirical factor 5 69.06 3 0.9944 5 68.67
8. Procedure
ALTERNATIVE METHOD FOR TOTAL LEAD AS
8.1 Weigh accurately (to 0.1 mg) 1 g of the sample into a
LEAD OXIDE—TITRIMETRIC METHOD
platinum dish. Add 5 mL of HNO and 10 mL of HF.
10. Apparatus
Cautiously evaporate to dryness on a steam bath. Repeat the
addition of HNO and HF and again cautiously evaporate to
3 10.1 Platinum Dish.
dryness. Wash the sides of the dish with a little water and
10.2 Filter Paper, ashless, medium texture, or paper pulp.
evaporate to dryness. Wet the residue with 5 mL of HNO ,
11. Reagents
warm gently, and transfer the residue to a 400-mL beaker using
a policeman. Neutralize with NH OH, and then make the
4 11.1 Ammonium Hydroxide (sp gr 0.90)—Concentrated am-
solution just acid with HCl, adding 5 mL in excess. Dilute to
monium hydroxide (NH OH).
200 mL and heat to just below the boiling point until solution
11.2 Glacial Acetic Acid (min 99.7 %)—Concentrated gla-
is complete.
cial acetic acid (CH COOH).
8.2 Pass H S through the solution for about 20 min. Filter,
11.3 Acid Ammonium Acetate Buffer—Mix 400 mL of
using paper pulp. Wash the precipitate five to six times with
distilled water and 400 mL of ammonium hydroxide (sp gr
water just acid with HCl and saturated with H S. Transfer the
2 0.90). Add 375 mL of reagent grade glacial acetic acid slowly
paper and precipitate to the original beaker, add 25 mL of
while stirring.
HNO , boil until the residue is white, then add 10 mL of H SO
3 2 4 11.4 Cupric Sulfate Solution (0.1 M)—Dissolve 25 g of
(1 + 1). Destroy the organic material by evaporating the
CuSO ·5H O in distilled water and dilute to 1 L.
solution to dense white fumes, making further additions of
11.5 Disodium Ethylenediaminetetracetate Dihydrate (0.05
HNO until there is no charring.
3 M) (EDTA solution) —Dissolve 18.6 g of the salt in distilled
8.3 Cool the solution, add 10 mL of water, and evaporate to
water and dilute to 1 L. Standardize the solution as follows:
fumes. Repeat the addition of water and the evaporation. Cool
Transfer 25 mL of lead standard (11.14) to a 400-mL beaker.
the solution, add 40 mL of water, and bring the solution to
Add concentrated ammonium hydroxide (11.1) dropwise until
boiling. Cool the solution and add 50 mL of isopropyl alcohol
a permanent precipitate just forms. Add 25 mL of acid
(98 %), stir, and allow the solution to stand cold for at least 4
ammonium acetate (11.3), dilute to 200 mL, heat to boiling,
h. Filter, using paper pulp, and wash once with cold isopropyl
add 4 drops of copper EDTA (11.7) and 12 drops of PAN
alcohol (50 %) containing 10 mL of H SO (sp gr 1.84)/100
2 4 (11.13) and titrate with the EDTA to a clear yellow.
mL.
1mLNa EDTA 5 0.2790/V g PbO
8.4 Transfer the precipitate to the original beaker with 150
mL of water, add 50 mL of the ammonium acetate solution, and
where:
boil the solution until the lead sulfate dissolves. Filter while hot V 5 EDTA required for titration, mL
through the original paper and wash well (6 to 8 washes) with g 5 lead oxide, g, and
hot water. To the filtrate add 5 mL of glacial acetic acid, heat
the solution to boiling, and add 20 mL of saturated K Cr O
2 2 7
solution. Boil the solution until the precipitate turns orange,
The standardized solution may also be purchased from Corco Chemical Corp.
and allow to stand on a warm plate for at least 2 h. Filter Catalog No.—Special.
D 1844
0.05 M 3 0.22321 5 0.01116 g PbO in 1 mL of lead 14. Precision and Bias
standard (10.14) (25 mL) (0.05 M) (0.22321) 5 0.2790 g PbO
14.1 On the basis of an interlaboratory study of the method
in 25 mL of lead standard (10.14).
in which operators in three laboratories analyzed two paints
11.6 Murexide Indicator Tablets—Ammonium salt of pur-
containing basic lead silicochromate with iron oxide the
puric acid.
following criteria should be used for judging the acceptability
11.7 Copper-EDTA Solution—Mix equivalent amounts of
of the results at the 95 % confidence level:
cupric sulfate solution (11.4) and EDTA solution (11.5) and
14.1.1 Repeatability—Two results, each the mean of dupli-
store in a dropping bottle. The cupric sulfate EDTA equiva-
cate determinations obtained by the same operator should be
lence may be determined as follows: Pipet 10 mL of cupric
considered suspect if they differ by more than the following:
sulfate into a beaker, add concentrated ammonium hydroxide
Percent Absolute PbO
dropwise until the precipitate which forms just redissolves.
28 % 0.20
45 % 0.30
Dilute to 200 mL with water, add two Murexide indicator
tablets, and titrate immediately with EDTA to a color change
14.1.2 Reproducibility—A realistic range could not be es-
from yellow to purple.
tablished for results between laboratories because of the
11.8 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro-
limited number of participating laboratories.
chloric acid (HCl) (see 7.4.1).
14.1.3 Bias—A bias statement could not be established
11.9 Hydrofluoric Acid (47 %)—Concentrated hydrofluoric
because of the limited number of participating laboratories.
acid (HF).
11.10 Hydrogen Sulfide (H S)—Cylinder. Handle and use in
CHROMIUM TRIOXIDE
a hood.
11.11 Hydrogen Sulfide Wash Solution— Add 10 mL of HCl 15. Interference
(sp gr 1.19) to 1 L of water and saturate with H S. +3
15.1 Soluble Fe will cause high results. See Section 20
11.12 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
.
(HNO ).
11.13 Pan Indicator (1-(2-pyridylazo)-2-naphthol)—
16. Reagents
Dissolve 0.1 g in 100 mL of ethanol.
16.1 Potassium Dichromate, Standard Solution (0.1 N)—
11.14 Primary Standard (0.05 M lead nitrate)—Dissolve
Weigh 4.904 g of dried potassium dichromate (K Cr O ),
2 2 7
16.5615 g of reagent grade lead nitrate in distilled water and
dissolve it in water, and dilute to 1 L with water in a volumetric
dilute to 1 L.
flask.
1mL 5 0.01116 g PbO
16.2 Potassium Iodide Solution (150 g/L)—Dissolve 150 g
11.15 Sulfuric Acid (1 + 1)—Carefully mix 1 volume of of potassium iodide (KI) in water and dilute to 1 L.
concentrated sulfuric acid (H SO , sp gr 1.84) with 1 volume
16.3 Hydrochloric Acid Mixture—Saturate water with NaCl
2 4
of water.
(about 350 g/L). To each litre of this solution add 150 mL of
water and 100 mL of concentrated HCl (sp gr 1.19).
12. Procedure
16.4 Sodium Thiosulfate Solution (0.1 N)—Dissolve 24.8 g
of reagent grade Na S O ·5H O in recently boiled water and
12.1 Dissolve1gof pigment in accordance with 8.1 and 2 2 3 2
dilute to 1 L with additional recently boiled water. To stan-
8.2.
dardize, pipet 25 mL of the standard potassium dichromate
12.2 Cool, so that the addition of 25 mL of water does not
solution (exactly 0.1000 N) into a 250-mL Erlenmeyer flask.
cause excessive splattering of the sulfuric acid; the solution at
Add 100 mL of water, 15 mL of potassium iodide solution, and
this point should be water white. Add ammonium hydroxide
15 mL of concentrated hydrochloric acid (sp gr 1.19). Titrate
(sp gr 0.90) until the pH of the solution is 5 to 5.5 (as indicated
the liberated iodine with sodium thiosulfate solution until the
by pH paper). Add 50 mL of acid ammonium acetate (11.3),
reddish-brown color becomes quite faint. Add 5 mL of starch
boil 5 min, dilute to 200 mL with water, heat to boiling, add 4
solution and continue the titration dropwise until the blue color
drops of copper-EDTA (11.7) and 12 drops of PAN
changes to a pale green. Calculate the normality of the sodium
(11.1311.13) and titrate while hot with standard EDTA to a
thiosulfate solution as follows:
clear yellow.
2.5000
N 5
M
13. Calculation
13.1 Calculate the percent lead oxide as follows:
where:
N 5 normality, and
V 3 L 3 100
PbO, % 5
M 5 sodium thiosulfate solution, mL,
S
16.5 Starch Indicator Solution—Make a homogeneous
where:
paste of 10 g of soluble starch in cold water. Add to this 1 L of
V 5 EDTA required for titration, mL,
boiling water, stir rapidly, and cool. Salicylic acid (1.25 g/L)
L 5 lead equivalent of EDTA solution, and
may be added to preserve the indicator. If long storage is
S 5 specimen weight, g.
required, the solution should be kept in a refrigerator at 4 to
D 1844
10°C (40 to 50°F). Prepare fresh indicator when the end point 20.5 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
of the titration from blue to colorless or blue to light green fails (HNO ).
to be sharp. 20.6 Perchloric Acid (sp gr 1.67)—Concentrated perchloric
acid (HClO ).
17. Procedure
20.7 Potassium Dichromate, Standard Solution (0.1 N)—
17.1 Weigh to 0.1 mg about1gof sample into a 500-mL See 16.1.
Erlenmeyer flask. Add 100 mL of NaCl-HCl solution and 20.8 Potassium Iodide Solution (150 g/Litre)—See 16.2.
dissolve the sample without heat, keeping the solution cold. 20.9 Sodium Thiosulfate Solution (0.1 N)—See 16.4.
(Silica will
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