ASTM D1844-86(2014)
(Test Method)Standard Test Methods for Chemical Analysis of Basic Lead Silicochromate
Standard Test Methods for Chemical Analysis of Basic Lead Silicochromate
SIGNIFICANCE AND USE
3.1 These test methods may be used to confirm the stated lead oxide, chromium trioxide and silica content of basic lead silicochromate and is useful for quality control.
SCOPE
1.1 These test methods cover the chemical analysis of the pigment commercially known as basic lead silicochromate and are applicable to pigment supplied by the manufacturer and to pigment, but not mixed pigments, separated from liquid coatings. The presence of basic lead silicochromate species shall be confirmed by X-ray diffraction analysis (see Specification D1648).
1.2 For liquid coatings the pigment must first be separated from the vehicle before conducting the analysis.
1.3 The analytical procedures appear in the following order:
Sections
Lead oxide
6 to 14
Chromium trioxide
15 to 23
Silica
24 to 27
Moisture and other volatile matter
28
Coarse particles
29
Oil absorption
30
Mass color and tinting strength
31
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D1844 − 86 (Reapproved 2014)
Standard Test Methods for
Chemical Analysis of Basic Lead Silicochromate
This standard is issued under the fixed designation D1844; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D387Test Method for Color and Strength of Chromatic
Pigments with a Mechanical Muller
1.1 These test methods cover the chemical analysis of the
D1193Specification for Reagent Water
pigment commercially known as basic lead silicochromate and
D1648SpecificationforBasicLeadSilicochromatePigment
are applicable to pigment supplied by the manufacturer and to
D2371 Test Method for Pigment Content of Solvent-
pigment, but not mixed pigments, separated from liquid
Reducible Paints
coatings. The presence of basic lead silicochromate species
shall be confirmed by X-ray diffraction analysis (see Specifi-
3. Significance and Use
cation D1648).
3.1 These test methods may be used to confirm the stated
1.2 For liquid coatings the pigment must first be separated
lead oxide, chromium trioxide and silica content of basic lead
from the vehicle before conducting the analysis.
silicochromate and is useful for quality control.
1.3 Theanalyticalproceduresappearinthefollowingorder:
4. Purity of Reagents
Sections
4.1 Reagent grade chemicals shall be used in all tests.
Lead oxide 6 to 14
Unlessotherwiseindicated,itisintendedthatallreagentsshall
Chromium trioxide 15 to 23
Silica 24 to 27
conform to the specifications of the Committee on Analytical
Moisture and other volatile matter 28
Reagents of the American Chemical Society, where such
Coarse particles 29
specifications are available. Other grades may be used, pro-
Oil absorption 30
Mass color and tinting strength 31
vided it is first ascertained that the reagent is of sufficiently
high purity to permit its use without lessening the accuracy of
1.4 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information the determination.
only.
4.2 Unless otherwise indicated, references to water shall be
1.5 This standard does not purport to address the safety understood to mean reagent water conforming to Type II of
Specification D1193.
concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and
5. Preparation of Sample
health practices and determine the applicability of regulatory
5.1 Thoroughly mix liquid coatings and separate in accor-
limitations prior to use.
dancewithTestMethodD2371sufficientpigmenttoenablethe
2. Referenced Documents required analyses to be carried out.
2.1 ASTM Standards: 5.2 Thoroughly mix pigment supplied as such and grind
separated pigment to a fine powder in a mortar and pestle
D185Test Methods for Coarse Particles in Pigments
D280Test 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
D281Test Method for Oil Absorption of Pigments by
METHOD
Spatula Rub-out
6. Apparatus
These test methods are under the jurisdiction of ASTM Committee D01 on
6.1 Glass Filtering Crucible(medium-porosityfritteddisk),
Paint and Related Coatings, Materials, and Applications and are the direct
dried to constant weight before use.
responsibility of Subcommittee D01.31 on Pigment Specifications.
Current edition approved Dec. 1, 2014. Published January 2015. Originally
approved in 1961. Last previous edition approved in 2008 as D1844–86(2008). Reagent Chemicals, American Chemical Society Specifications , American
DOI: 10.1520/D1844-86R14. Chemical Society, Washington, DC. For suggestions on the testing of reagents not
For referenced ASTM standards, visit the ASTM website, www.astm.org, or listed by the American Chemical Society, see Analar Standards for Laboratory
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Standards volume information, refer to the standard’s Document Summary page on and National Formulary,U.S.PharmacopeialConvention,Inc.,(USPC),Rockville,
the ASTM website. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1844 − 86 (2014)
6.2 Platinum Dish. through the original paper and wash well (6 to 8 washes) with
hot water. To the filtrate add 5 mL of glacial acetic acid, heat
7. Reagents 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,
7.1 Acetic Acid (Glacial).
and allow to stand on a warm plate for at least 2 h. Filter
7.2 Ammonium Hydroxide (sp gr 0.90)—Concentrated am-
through a glass filtering crucible (medium-porosity fritted
monium hydroxide (NH OH).
disk), wash three times with hot water, and finally once with
7.3 AmmoniumAcetate,Acid Solution—To300mLofwater alcohol. Dry in an oven at 105°C for 2 h, cool, and weigh.
add an equal volume of NH OH. Neutralize with glacial acetic
9. Calculation
acid and add 20 mL in excess.
9.1 Calculatethepercentoftotalleadasleadoxide(PbO)as
7.4 Hydrochloric Acid (sp gr 1.19)—Concentrated hydro-
follows:
chloric acid (HCl).
PbO, % 5 ~P 369.06!/S
7.5 Hydrofluoric Acid (47 %)—Concentrated hydrofluoric
acid (HF).
where:
7.6 Hydrogen Sulfide (H S)—Handle and use H S in hood. P = lead chromate (PbCrO ) precipitate, g,
2 2 4
S = sample used, g, and
7.7 Isopropyl Alcohol (50 and 98%).
molecularweight PbO
~ !
7.8 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
molecularweight ~PbCrO !
(HNO ).
223.21
5 0.6906 3100 forpercent 5 69.06
~ !
7.9 Potassium Dichromate Solution (saturated)—Prepare a
323.21
saturatedsolutionofpotassiumdichromate(K Cr O )inwater.
2 2 7
69.06 represents the gravimetric factor to convert grams of
7.10 Sulfuric Acid (1 + 1)—Carefully mix 1 volume of
PbCrO to grams of PbO.
concentrated sulfuric acid (H SO , sp gr 1.84) with 1 volume
2 4
This gravimetric factor has led to high results due to the
of water.
presence of mixed lead chromates and an empirical factor can
be used to compensate:
8. Procedure
Empiricalfactor 5 69.06 30.9944 5 68.67
8.1 Weigh accurately (to 0.1 mg)1gofthe sample into a
ALTERNATIVE METHOD FOR TOTAL LEAD AS
platinum dish. Add 5 mL of HNO and 10 mL of HF.
Cautiously evaporate to dryness on a steam bath. Repeat the LEADOXIDE—TITRIMETRIC METHOD
addition of HNO and HF and again cautiously evaporate to
10. Apparatus
dryness. Wash the sides of the dish with a little water and
evaporate to dryness. Wet the residue with 5 mL of HNO , 10.1 Platinum Dish.
warmgently,andtransfertheresiduetoa400-mLbeakerusing
10.2 Filter Paper, ashless, medium texture, or paper pulp.
a policeman. Neutralize with NH OH, and then make the
solution just acid with HCl, adding 5 mL in excess. Dilute to
11. Reagents
200 mL and heat to just below the boiling point until solution
11.1 Ammonium Hydroxide (sp gr 0.90)—Concentrated am-
is complete.
monium hydroxide (NH OH).
8.2 Pass H S through the solution for about 20 min. Filter,
11.2 Glacial Acetic Acid (min 99.7 %)—Concentrated gla-
using paper pulp. Wash the precipitate five to six times with
cial acetic acid (CH COOH).
water just acid with HCl and saturated with H S. Transfer the
11.3 Acid Ammonium Acetate Buffer—Mix 400 mL of dis-
paper and precipitate to the original beaker, add 25 mL of
tilled water and 400 mLof ammonium hydroxide (sp gr 0.90).
HNO ,boiluntiltheresidueiswhite,thenadd10mLofH SO
3 2 4
Add 375 mL of reagent grade glacial acetic acid slowly while
(1+1). Destroy the organic material by evaporating the
stirring.
solution to dense white fumes, making further additions of
HNO until there is no charring.
11.4 Cupric Sulfate Solution (0.1 M)—Dissolve 25 g of
CuSO ·5H O in distilled water and dilute to 1 L.
8.3 Cool the solution, add 10 mLof water, and evaporate to 4 2
fumes. Repeat the addition of water and the evaporation. Cool
11.5 Disodium Ethylenediaminetetracetate Dihydrate (0.05
the solution, add 40 mL of water, and bring the solution to
M) (EDTA solution) —Dissolve 18.6 g of the salt in distilled
boiling. Cool the solution and add 50 mLof isopropyl alcohol
water and dilute to 1 L. Standardize the solution as follows:
(98%), stir, and allow the solution to stand cold for at least 4
Transfer 25 mL of lead standard (11.14) to a 400-mL beaker.
h. Filter, using paper pulp, and wash once with cold isopropyl
Add concentrated ammonium hydroxide (11.1) dropwise until
alcohol (50%) containing 10 mL of H SO (sp gr 1.84)/100
2 4 a permanent precipitate just forms. Add 25 mL of acid
mL.
ammonium acetate (11.3), dilute to 200 mL, heat to boiling,
8.4 Transfer the precipitate to the original beaker with 150
mLofwater,add50mLoftheammoniumacetatesolution,and
The standardized solution may also be purchased from Corco Chemical Corp.
boilthesolutionuntiltheleadsulfatedissolves.Filterwhilehot Catalog No.—Special.
D1844 − 86 (2014)
add 4 drops of copper EDTA (11.7) and 12 drops of PAN 13. Calculation
(11.13) and titrate with the EDTA to a clear yellow.
13.1 Calculate the percent lead oxide as follows:
1mLNa EDTA 5 0.2790/V g PbO
V 3L 3100
PbO, % 5
S
where:
V = EDTA required for titration, mL
where:
g = lead oxide, g, and
V = EDTA required for titration, mL,
0.05 M×0.22321=0.01116gPbOin1mLofleadstandard L = lead equivalent of EDTA solution, and
(11.14). S = specimen weight, g.
25 mL × 0.05 M × 0.22321g/mmol =0.2790 g PbO in 25
14. Precision and Bias
mL of lead standard (11.14).
14.1 On the basis of an interlaboratory study of the method
11.6 Murexide Indicator Tablets—Ammonium salt of pur-
in which operators in three laboratories analyzed two paints
puric acid.
containing basic lead silicochromate with iron oxide the
11.7 Copper-EDTA Solution—Mix equivalent amounts of
following criteria should be used for judging the acceptability
cupric sulfate solution (11.4) and EDTA solution (11.5) and
of the results at the 95% confidence level:
store in a dropping bottle. The cupric sulfate EDTA equiva-
14.1.1 Repeatability—Two results, each the mean of dupli-
lence may be determined as follows: Pipet 10 mL of cupric
cate determinations obtained by the same operator should be
sulfate into a beaker, add concentrated ammonium hydroxide
considered suspect if they differ by more than the following:
dropwise until the precipitate which forms just redissolves.
Percent Absolute PbO
Dilute to 200 mL with water, add two Murexide indicator
28 % 0.20
45 % 0.30
tablets, and titrate immediately with EDTA to a color change
from yellow to purple.
14.1.2 Reproducibility—A realistic range could not be es-
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).
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).
CHROMIUM TRIOXIDE
11.10 Hydrogen Sulfide (H S)—Cylinder. Handle and use in
a hood.
15. Interference
+3
11.11 Hydrogen Sulfide Wash Solution—Add 10 mLof HCl
15.1 Soluble Fe will cause high results. See Section 20.
(sp gr 1.19) to 1 L of water and saturate with H S.
16. Reagents
11.12 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
(HNO ).
16.1 Potassium Dichromate, Standard Solution (0.1 N)—
Weigh 4.904 g of dried potassium dichromate (K Cr O ),
2 2 7
11.13 Pan Indicator (1-(2-pyridylazo)-2-naphthol)—
dissolveitinwater,anddiluteto1Lwithwaterinavolumetric
Dissolve 0.1 g in 100 mL of ethanol.
flask.
11.14 Primary Standard (0.05 M lead nitrate)—Dissolve
16.2 Potassium Iodide Solution (150 g/L)—Dissolve 150 g
16.5615 g of reagent grade lead nitrate in distilled water and
of potassium iodide (KI) in water and dilute to 1 L.
dilute to 1 L.
16.3 Hydrochloric Acid Mixture—Saturate water with NaCl
1mL 5 0.01116g PbO
(about 350 g/L). To each litre of this solution add 150 mL of
11.15 Sulfuric Acid (1 + 1)—Carefully mix 1 volume of
water and 100 mL of concentrated HCl (sp gr 1.19).
concentrated sulfuric acid (H SO , sp gr 1.84) with 1 volume
2 4
16.4 Sodium Thiosulfate Solution (0.1 N)—Dissolve 24.8 g
of water.
of reagent grade Na S O ·5H O in recently boiled water and
2 2 3 2
dilute to 1 L with additional recently boiled water. To
12. Procedure
standardize,pipet25mLofthestandardpotassiumdichromate
12.1 Dissolve1gof pigment in accordance with 8.1 and
solution (exactly 0.1000 N) into a 250-mL Erlenmeyer flask.
8.2.
Add100mLofwater,15mLofpotassiumiodidesolution,and
15 mL of concentrated hydrochloric acid (sp gr 1.19). Titrate
12.2 Cool, so that the addition of 25 mL of water does not
the liberated iodine with sodium thiosulfate solution until the
cause excessive splattering of the sulfuric acid; the solution at
reddish-brown color becomes quite faint. Add 5 mL of starch
this point should be water white. Add ammonium hydroxide
solutionandcontinuethetitrationdropwiseuntilthebluecolor
(spgr0.90)untilthepHofthesolutionis5to5.5(asindicated
changes to a pale green. Calculate the normality of the sodium
by pH paper). Add 50 mL of acid ammonium acetate (11.3),
thiosulfate solution as follows:
boil 5 min, dilute to 200 mLwith water, heat to boiling, add 4
2.5000
dropsofcopper-EDTA(11.7)and12dropsofPAN(11.13)and
N 5
titrate while hot with standard EDTA to a clear yellow. M
D1844 − 86 (2014)
where: 20. Reagents
N = normality, and
20.1 Ammonium Hydroxide (sp gr 0.90)—Concentrated am-
M = sodium thiosulfate solution, mL,
monium hydroxide (NH OH).
16.5 StarchIndicatorSolution—Makeahomogeneouspaste
20.2 Disodium Ethylenediaminetetracetate Dihydrate
of 10 g of soluble starch in cold water. Add to this 1 L of
(0.05 M) (EDTA)—Dissolve 18.6 g of the reagent grade salt in
boiling water, stir rapidly, and cool. Salicylic acid (1.25 g/L)
distilled water and dilute to 1 L. See 11.5 for standardization.
may be added to preserve the indicator. If long storage is
20.3 Hydrochloric Acid Mixture—See 16.3.
required, the solution should be kept in a refrigerator at 4 to
20.4 Hydrofluoric Acid (47 %)—Concentrated hydrofluoric
10°C (40 to 50°F). Prepare fresh indicator when the end point
acid (HF).
ofthetitrationfrombluetocolorlessorbluetolightgreenfails
to be sharp.
20.5 Nitric Acid (sp gr 1.42)—Concentrated nitric acid
(HNO ).
17. Procedure
20.6 Perchloric Acid (sp gr 1.67)—Concent
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D1844 − 86 (Reapproved 2008) D1844 − 86 (Reapproved 2014)
Standard Test Methods for
Chemical Analysis of Basic Lead Silicochromate
This standard is issued under the fixed designation D1844; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These test methods cover the chemical analysis of the pigment commercially known as basic lead silicochromate and are
applicable to pigment supplied by the manufacturer and to pigment, but not mixed pigments, separated from liquid coatings. The
presence of basic lead silicochromate species shall be confirmed by X-ray diffraction analysis (see Specification D1648).
1.2 For liquid coatings the pigment must first be separated from the vehicle before conducting the analysis.
1.3 The analytical procedures appear in the following order:
Sections
Sections
Lead oxide 6 to 14
Chromium trioxide 15 to 23
Silica 24 to 27
Moisture and other volatile matter 28
Coarse particles 29
Oil absorption 30
Mass color and tinting strength 31
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the
user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations
prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D185 Test Methods for Coarse Particles in Pigments
D280 Test Methods for Hygroscopic Moisture (and Other Matter Volatile Under the Test Conditions) in Pigments
D281 Test Method for Oil Absorption of Pigments by Spatula Rub-out
D387 Test Method for Color and Strength of Chromatic Pigments with a Mechanical Muller
D1193 Specification for Reagent Water
D1648 Specification for Basic Lead Silicochromate Pigment
D2371 Test Method for Pigment Content of Solvent-Reducible Paints
3. Significance and Use
3.1 These test methods may be used to confirm the stated lead oxide, chromium trioxide and silica content of basic lead
silicochromate and is useful for quality control.
4. Purity of Reagents
4.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform
to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are
These test methods are under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and are the direct responsibility of
Subcommittee D01.31 on Pigment Specifications.
Current edition approved July 1, 2008Dec. 1, 2014. Published August 2008January 2015. Originally approved in 1961. Last previous edition approved in 20032008 as
D1844 – 86 (2003).(2008). DOI: 10.1520/D1844-86R08.10.1520/D1844-86R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1844 − 86 (2014)
available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use
without lessening the accuracy of the determination.
4.2 Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to Type II of
Specification D1193.
5. Preparation of Sample
5.1 Thoroughly mix liquid coatings and separate in accordance with Test Method D2371 sufficient pigment to enable the
required analyses to be carried out.
5.2 Thoroughly mix pigment supplied as such and grind separated pigment to a fine powder in a mortar and pestle before taking
portions for analysis.
TOTAL LEAD AS LEAD OXIDE-GRAVIMETRIC METHOD
6. Apparatus
6.1 Glass Filtering Crucible (medium-porosity fritted disk), dried to constant weight before use.
6.2 Platinum Dish.
7. Reagents
7.1 Acetic Acid (Glacial).
7.2 Ammonium Hydroxide (sp gr 0.90)—Concentrated ammonium hydroxide (NH OH).
7.3 Ammonium Acetate, Acid Solution—To 300 mL of water add an equal volume of NH OH. Neutralize with glacial acetic acid
and add 20 mL in excess.
7.4 Hydrochloric Acid (sp gr 1.19)—Concentrated hydrochloric acid (HCl).
7.5 Hydrofluoric Acid (47 %)—Concentrated hydrofluoric acid (HF).
7.6 Hydrogen Sulfide (H S)—Handle and use H S in hood.
2 2
7.7 Isopropyl Alcohol (50 and 98 %).
7.8 Nitric Acid (sp gr 1.42)—Concentrated nitric acid (HNO ).
7.9 Potassium Dichromate Solution (saturated)—Prepare a saturated solution of potassium dichromate (K Cr O ) in water.
2 2 7
7.10 Sulfuric Acid (1 + 1)—Carefully mix 1 volume of concentrated sulfuric acid (H SO , sp gr 1.84) with 1 volume of water.
2 4
8. Procedure
8.1 Weigh accurately (to 0.1 mg) 1 g of the sample into a platinum dish. Add 5 mL of HNO and 10 mL of HF. Cautiously
evaporate to dryness on a steam bath. Repeat the addition of HNO and HF and again cautiously evaporate to dryness. Wash the
sides of the dish with a little water and evaporate to dryness. Wet the residue with 5 mL of HNO , warm gently, and transfer the
residue to a 400-mL beaker using a policeman. Neutralize with NH OH, and then make the solution just acid with HCl, adding
5 mL in excess. Dilute to 200 mL and heat to just below the boiling point until solution is complete.
8.2 Pass H S through the solution for about 20 min. Filter, using paper pulp. Wash the precipitate five to six times with water
just acid with HCl and saturated with H S. Transfer the paper and precipitate to the original beaker, add 25 mL of HNO , boil until
2 3
the residue is white, then add 10 mL of H SO (1 + 1). Destroy the organic material by evaporating the solution to dense white
2 4
fumes, making further additions of HNO until there is no charring.
8.3 Cool the solution, add 10 mL of water, and evaporate to fumes. Repeat the addition of water and the evaporation. Cool the
solution, add 40 mL of water, and bring the solution to boiling. Cool the solution and add 50 mL of isopropyl alcohol (98 %), stir,
and allow the solution to stand cold for at least 4 h. Filter, using paper pulp, and wash once with cold isopropyl alcohol (50 %)
containing 10 mL of H SO (sp gr 1.84)/100 mL.
2 4
8.4 Transfer the precipitate to the original beaker with 150 mL of water, add 50 mL of the ammonium acetate solution, and boil
the solution until the lead sulfate dissolves. Filter while hot through the original paper and wash well (6 to 8 washes) with 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 solution. Boil the
2 2 7
solution until the precipitate turns orange, and allow to stand on a warm plate for at least 2 h. Filter through a glass filtering crucible
(medium-porosity fritted disk), wash three times with hot water, and finally once with alcohol. Dry in an oven at 105°C for 2 h,
cool, and weigh.
Reagent Chemicals, American Chemical Society Specifications , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc., (USPC), Rockville, MD.
D1844 − 86 (2014)
9. Calculation
9.1 Calculate the percent of total lead as lead oxide (PbO) as follows:
PbO, %5 P 369.06 /S
~ !
where:
P = lead chromate (PbCrO ) precipitate, g,
S = sample used, g, and
molecular weight ~PbO!
molecular weight PbCrO
~ !
223.21
5 0.6906 3100 ~for percent!5 69.06
323.21
69.06 represents the gravimetric factor to convert grams of PbCrO to grams of PbO.
This gravimetric factor has led to high results due to the presence of mixed lead chromates and an empirical factor can be used
to compensate:
Empirical factor 5 69.06 30.9944 5 68.67
ALTERNATIVE METHOD FOR TOTAL LEAD AS LEADOXIDE—TITRIMETRIC METHOD
10. Apparatus
10.1 Platinum Dish.
10.2 Filter Paper, ashless, medium texture, or paper pulp.
11. Reagents
11.1 Ammonium Hydroxide (sp gr 0.90)—Concentrated ammonium hydroxide (NH OH).
11.2 Glacial Acetic Acid (min 99.7 %)—Concentrated glacial acetic acid (CH COOH).
11.3 Acid Ammonium Acetate Buffer—Mix 400 mL of distilled water and 400 mL of ammonium hydroxide (sp gr 0.90). Add
375 mL of reagent grade glacial acetic acid slowly while stirring.
11.4 Cupric Sulfate Solution (0.1 M)—Dissolve 25 g of CuSO ·5H O in distilled water and dilute to 1 L.
4 2
11.5 Disodium Ethylenediaminetetracetate Dihydrate (0.05 M) (EDTA solution) —Dissolve 18.6 g of the salt in distilled water
and dilute to 1 L. Standardize the solution as follows: Transfer 25 mL of lead standard (11.14) to a 400-mL beaker. Add
concentrated ammonium hydroxide (11.1) dropwise until a permanent precipitate just forms. Add 25 mL of acid ammonium acetate
(11.3), dilute to 200 mL, heat to boiling, add 4 drops of copper EDTA (11.7) and 12 drops of PAN (11.13) and titrate with the EDTA
to a clear yellow.
1 mL Na EDTA 5 0.2790/V g PbO
where:
V = EDTA required for titration, mL
g = lead oxide, g, and
0.05 M × 0.22321 = 0.01116 g PbO in 1 mL of lead standard (11.14).
25 mL × 0.05 M × 0.22321g/mmol = 0.2790 g PbO in 25 mL of lead standard (11.14).
11.6 Murexide Indicator Tablets—Ammonium salt of purpuric acid.
11.7 Copper-EDTA Solution—Mix equivalent amounts of cupric sulfate solution (11.4) and EDTA solution (11.5) and store in
a dropping bottle. The cupric sulfate EDTA equivalence may be determined as follows: Pipet 10 mL of cupric sulfate into a beaker,
add concentrated ammonium hydroxide dropwise until the precipitate which forms just redissolves. Dilute to 200 mL with water,
add two Murexide indicator tablets, and titrate immediately with EDTA to a color change from yellow to purple.
11.8 Hydrochloric Acid (sp gr 1.19)—Concentrated hydrochloric acid (HCl).
11.9 Hydrofluoric Acid (47 %)—Concentrated hydrofluoric acid (HF).
11.10 Hydrogen Sulfide (H S)—Cylinder. Handle and use in a hood.
11.11 Hydrogen Sulfide Wash Solution—Add 10 mL of HCl (sp gr 1.19) to 1 L of water and saturate with H S.
11.12 Nitric Acid (sp gr 1.42)—Concentrated nitric acid (HNO ).
The standardized solution may also be purchased from Corco Chemical Corp. Catalog No.—Special.
D1844 − 86 (2014)
11.13 Pan Indicator (1-(2-pyridylazo)-2-naphthol)—Dissolve 0.1 g in 100 mL of ethanol.
11.14 Primary Standard (0.05M lead nitrate)—Dissolve 16.5615 g of reagent grade lead nitrate in distilled water and dilute to
1 L.
1 mL 5 0.01116 g PbO
11.15 Sulfuric Acid (1 + 1)—Carefully mix 1 volume of concentrated sulfuric acid (H SO , sp gr 1.84) with 1 volume of water.
2 4
12. Procedure
12.1 Dissolve 1 g of pigment in accordance with 8.1 and 8.2.
12.2 Cool, so that the addition of 25 mL of water does not cause excessive splattering of the sulfuric acid; the solution at this
point should be water white. Add ammonium hydroxide (sp gr 0.90) until the pH of the solution is 5 to 5.5 (as indicated by pH
paper). Add 50 mL of acid ammonium acetate (11.3), boil 5 min, dilute to 200 mL with water, heat to boiling, add 4 drops of
copper-EDTA (11.7) and 12 drops of PAN (11.13) and titrate while hot with standard EDTA to a clear yellow.
13. Calculation
13.1 Calculate the percent lead oxide as follows:
V 3L 3100
PbO, %5
S
where:
V = EDTA required for titration, mL,
L = lead equivalent of EDTA solution, and
S = specimen weight, g.
14. Precision and Bias
14.1 On the basis of an interlaboratory study of the method in which operators in three laboratories analyzed two paints
containing basic lead silicochromate with iron oxide the following criteria should be used for judging the acceptability of the
results at the 95 % confidence level:
14.1.1 Repeatability—Two results, each the mean of duplicate determinations obtained by the same operator should be
considered suspect if they differ by more than the following:
Percent Absolute PbO
28 % 0.20
45 % 0.30
14.1.2 Reproducibility—A realistic range could not be established for results between laboratories because of the limited number
of participating laboratories.
14.1.3 Bias—A bias statement could not be established because of the limited number of participating laboratories.
CHROMIUM TRIOXIDE
15. Interference
+3
15.1 Soluble Fe will cause high results. See Section 20.
16. Reagents
16.1 Potassium Dichromate, Standard Solution (0.1 N)—Weigh 4.904 g of dried potassium dichromate (K Cr O ), dissolve it
2 2 7
in water, and dilute to 1 L with water in a volumetric flask.
16.2 Potassium Iodide Solution (150 g/L)—Dissolve 150 g of potassium iodide (KI) in water and dilute to 1 L.
16.3 Hydrochloric Acid Mixture—Saturate water with NaCl (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).
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 dilute
2 2 3 2
to 1 L with additional recently boiled water. To standardize, pipet 25 mL of the standard potassium dichromate solution (exactly
0.1000 N) into a 250-mL Erlenmeyer flask. Add 100 mL of water, 15 mL of potassium iodide solution, and 15 mL of concentrated
hydrochloric acid (sp gr 1.19). Titrate the liberated iodine with sodium thiosulfate solution until the reddish-brown color becomes
quite faint. Add 5 mL of starch solution and continue the titration dropwise until the blue color changes to a pale green. Calculate
the normality of the sodium thiosulfate solution as follows:
2.5000
N 5
M
D1844 − 86 (2014)
where:
N = normality, and
M = sodium thiosulfate solution, mL,
16.5 Starch Indicator Solution—Make a homogeneous paste of 10 g of soluble starch in cold water. Add to this 1 L of boiling
water, stir rapidly, and cool. Salicylic acid (1.25 g/L) may be added to preserve the indicator. If long storage is required, the solution
should be kept in a
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