ASTM D444-88(2014)

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: D444 − 88 (Reapproved 2008) D444 − 88 (Reapproved 2014)
Standard Test Methods for
Chemical Analysis of Zinc Yellow Pigment (Zinc Chromate
Yellow)
This standard is issued under the fixed designation D444; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 These test methods cover procedures for the chemical analysis of the pigment known commercially as “zinc yellow” or
“zinc chromate yellow.”
1.2 The analytical procedures appear in the following order:
Sections
Moisture and Other Volatile Matter 7
Combined Water 8
Chromium:
Dichromate Method 9 – 11
Thiosulfate Method 9, 12, and 13
Zinc:
Hydroxyquinoline Method 9, 14, and 15
Ferrocyanide Method 9, 16, and 17
Alkaline Salts 18 and 19
Sulfates 20 and 21
Chlorides 22 and 23
Matter Insoluble in Dilute Acetic 24
Acid
Coarse Particles 25
1.3 The values stated in SI units are to be considered the standard. The values given in parentheses are for information only.
1.4 This standard does not purport to address all of 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
D478 Specification for Zinc Yellow (Zinc Chromate) Pigments
D1193 Specification for Reagent Water
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
E50 Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials
3. Significance and Use
3.1 This test method has been developed to standardize the chemical analysis of zinc chromate yellow pigment and to provide
alternate methods of analysis for chromium and zinc.
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 Feb. 1, 2008Dec. 1, 2014. Published February 2008December 2014. Originally approved in 1937. Last previous edition approved in 20032008
as D444 – 88 (2003).(2008). DOI: 10.1520/D0444-88R08.10.1520/D0444-88R14.
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’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
D444 − 88 (2014)
4. Preparation of Sample
4.1 Mix the laboratory sample thoroughly. Take a sufficient quantity for the chemical analyses and pass it through a 180-μm (No.
80) sieve, grinding in a mortar if necessary.
NOTE 1—Detailed requirements for this sieve are given in Specification E11.
5. Reagents
5.1 Purity of Reagents—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 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.
5.2 Purity of Water—Unless otherwise indicated, references to water for use in the preparation of reagents and in analytical
procedures shall conform to Type II reagent water, in Specification D1193.
6. Precision
6.1 Precision statements have not been established.
MOISTURE AND OTHER VOLATILE MATTER
7. Procedure
7.1 Determine moisture and other volatile matter in accordance with Test Method A of Test Methods D280.
COMBINED WATER
8. Procedure
8.1 Weigh to 0.1 mg 3 g of the oven-dried material from the determination of moisture and other volatile matter (Note 2 and
Note 3), and place in a porcelain boat. Introduce the boat with the charge into a refractory combustion tube in an electrically-heated
combustion furnace of the type used for the determination of carbon in steel by direct combustion (Note 4). Place the boat at the
center of the combustion tube maintained at a temperature of 1000°C for 4 h. Draw a current of pure dry air or dry nitrogen through
the tube to sweep the evolved moisture into a previously weighed absorption tube containing anhydrous magnesium perchlorate
(Mg(ClO ) ) or other efficient desiccant. The weight increase of the absorption tube represents the “combined water.”
4 2
NOTE 2—Loss on ignition of the pigment does not suffice for the determination of combined water in zinc yellow.
NOTE 3—If the pigment contains an organic treating agent, first remove this treating agent by washing with ether or chloroform.
NOTE 4—See Apparatus No. 1 for the determination of total carbon by direct combustion as described in Practices E50.
SPECIMEN SOLUTION FOR DETERMINATION OF
CHROMIUM AND ZINC
9. Procedure
9.1 Weigh to 0.1 mg about a 4-g specimen and mix with 50 mL of cold sulfuric acid (H SO ) (1+5). It should dissolve
2 4
completely at this stage (Note 5). Dilute the solution to 500 mL in a volumetric flask.
NOTE 5—A cloudy solution may result if the pigment contains a surface-treating agent. In this case, it usually can be cleared by cooling in an ice-bath
and filtering through a medium porosity fritted disk. If the solution is not clarified by this treatment, extract a portion of the original sample with a solvent
such as chloroform before the analysis is begun.
CHROMIUM BY THE DICHROMATE TEST METHOD
10. Reagents
10.1 Ferrous Ammonium Sulfate Solution—Dissolve 80 g of ferrous ammonium sulfate (FeSO · (NH ) SO · 6H O) in 50 mL
4 4 2 4 2
of H SO (sp gr 1.84) and enough water to make 1 L of solution. Mix thoroughly before use. This solution is approximately 0.2
2 4
N.
10.2 Ortho-Phenanthroline Indicator Solution—0.5 % in water.
10.3 Potassium Dichromate, Standard Solution—(0.1 N)—Dissolve 4.9035 g of dried potassium dichromate (K Cr O ) in water
2 2 7
and dilute to 1 L in a volumetric flask.
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.
D444 − 88 (2014)
11. Procedure
11.1 Pipet 50 mL of the solution of the specimen (Section 7) into a 600-mL beaker. Add 200 to 250 mL of water and 10 mL
of H SO (sp gr 1.84). Cool to 35°C or below.
2 4
11.2 Add an excess of ferrous ammonium sulfate solution and back-titrate with 0.1 N K Cr O solution, using orthophenan-
2 2 7
throline indicator. Carry out a blank titration of the same amount of ferrous ammonium sulfate solution at the same time and in
the same manner.
11.3 Calculation—Calculate the percent of chromium C as CrO , as follows:
C 5 B 2 V N 30.03334/S 3100
~ !
1 1 1 1
where:
B = K Cr O solution required for titration of the blank, mL,
1 2 2 7
V = K Cr O solution required for back-titration of the specimen, mL,
1 2 2 7
N = normality of the K Cr O solution, and
1 2 2 7
S = specimen in the aliquot used, g.
0.03334 = milliequivalents weight of CrO .
11.4 Alternatively, the solution of the specimen may be titrated directly with the ferrous ammonium sulfate solution, using an
electrometric titration assembly to detect the end point. Standardize the ferrous solution against K Cr O .
2 2 7
CHROMIUM BY THE THIOSULFATE TEST METHOD
12. Reagents
12.1 Potassium Iodide Solution (150 g/L)—Dissolve 150 g of potassium iodide (KI) in water and dilute to 1 L.
12.2 Sodium Thiosulfate, Standard Solution (0.1 N)—Dissolve 24.8 g of sodium thiosulfate of (Na S O · 5H O) in 1 L of
2 2 3 2
freshly boiled and cooled water contained in a sterile glass bottle. If sulfur precipitates during preparation or upon subsequent use,
discard the solution and prepare a new one. Standardize against iodine.
12.3 Starch Indicator Solution—Stir up 2 to 3 g of potato starch with 100 mL salicylic acid solution (1 %), and boil the mixture
until the starch is practically dissolved, then dilute to 1 L with water.
13. Procedure
13.1 Pipet a 25-mL aliquot of the solution of the specimen (Section 9) into a 500-mL glass-stoppered Erlenmeyer iodimetric
flask or other suitable glass-stoppered bottle containing 200 mL of H SO (1+39). Add 20 mL of KI solution (150 g/L), stopper,
2 4
and allow the solution to stand for approximately 5 min.
13.2 Titrate the liberated iodine with 0.1 NNa S O solution at room temperature until the reddish brown iodine color becomes
2 2 3
quite faint. Add 5 mL of starch solution and continue the titration until the final color change becomes pale green with no blue
tinge. Titrate this final titration by swirling the flask at least three times after each addition of the Na S O solution, being sure
2 2 3
that there is no further color change, especially at the final stage of the titration. The green end point is definite and sharp.
13.3 Calculation—Calculate the percent of chromium C as CrO as follows:
C 5 @ V N 30.03334 /S # 3100
~ !
2 2 2
where:
V = Na S O solution required for titration of the specimen, mL
2 2 2 3
N = normality of the Na S O solution, and
2 2 2 3
S = specimen in the aliquot used, g.
ZINC BY THE HYDROXYQUINOLINE TEST METHOD
(Suitable if No Interfering Substances Are Present)
14. Reagents
14.1 Acetone Solution of 8-Hydroxyquinoline (50 g/L)—Dissolve 5 g of 8-hydroxyquinoline in 100 mL of acetone.
15. Procedure
15.1 Pipet 50 mL of the solution of the specimen (Section 9) into a 250-mL beaker and dilute to 100 mL with water. Add 5 to
10 g of ammonium chloride (NH Cl) and heat to boiling. Add a slight excess of ammonium hydroxide (NH OH) and let stand a
4 4
few minutes to allow any precipitate to coagulate. Filter through an ashless, rapid paper into a 400-mL beaker and wash.
D444 − 88 (2014)
15.2 Heat the filtrate to boiling and add 5 mL of NH OH (sp gr 0.90). Add dropwise 10 mL of the acetone solution of
8-hydroxyquinoline (Note 6). Let stand 10 to 20 min and filter through a medium-porosity sintered-glass crucible. Wash well with
water.
NOTE 6—The reagent is used in acetone solution rather than alcohol solution to eliminate the danger of reducing some of the chromate by alcohol.
Avoid adding an excess of reagent and lengthy boiling after its addition. Ten millilitres of hydroxyquinoline (50 g/L) is sufficient for a normal zinc yellow.
The solution can be tested for complete precipitation, but since the reagent itself is rather insoluble, the results may be misleading. The insoluble reagent
will dissolve in a hot solution and also in an excess of alcohol or acetone, whereas the zinc oxyquinolate will not.
15.3 Dry the precipitate at 165°C for at least 2 h and weigh as zinc oxyquinolate.
15.4 Calculation—Calculate the percent zinc A as zinc oxide (ZnO), as follows:
A 5 P 30.2303 /S 3100
@~ ! #
where:
P = zinc oxyquinolate, g, and
S = specimen in aliquot used, g.
0.2303 = ZnO/zinc oxyquinolate = 81.38 ⁄353.37
ZINC BY THE FERROCYANIDE TEST METHOD
16. Reagents
16.1 Methyl Orange Indicator Solution—Dissolve 0.1 g of methyl orange in 100 mL of water.
16.2 Potassium Ferrocyanide, Standard Solution—Dissolve 22 g of potassium ferrocyanide (K Fe(CN) · 3H O) in water and
4 6 2
dilute to 1 L. To standardize, transfer 0.2 g of metallic zinc or freshly ignited ZnO to a 400-mL beaker. Dissolve in 10 mL of
hydrochloric acid (HCl, sp gr 1.19) and 20 mL of water. Drop in a small piece of litmus paper, add ammonium hydroxide (NH OH)
until slightly alkaline, then add HCl until just acid, and then 3 mL more of HCl. Dilute to about 250 mL with hot water and heat
nearly to boiling. Run in the K Fe(CN) solution slowly from a buret, while stirring constantly, until a drop tested on a white
4 6
porcelain plate with a drop of the uranyl indicator solution shows a brown tinge after standing 1 min. Do not allow the temperature
of the solution to fall below 70°C during the titration. Run a blank using the same amounts of reagents and water as in the
standardization. The standardization must be made under the same conditions of temperature, volume, and acidity as obtained
when the specimen is titrated. Calculate the strength of the K Fe(CN) solution in terms of grams of zinc as follows:
4 6
Z 5 W/ V 2 B
~ !
3 2
where:
Z = zinc equivalent of the K Fe(CN) solution, g/mL,
4 6
W = zinc used (or equivalent to the ZnO used), g,
V = K Fe(CN) solution required for titration of the standard, g, and
3 4 6
B = K Fe(CN) solution required for titration of the blank, mL.
2 4 6
16.3 Thymol Blue Indicator Solution (0.5 g/L)—Dissolve 0.1 g of thymol blue indicator in 200-mL of methanol, ethanol, or
isopropanol.
16.4 Uranyl Acetate Indicator Solution (50 g/L)—Dissolve 5 g of UO (C H O ) · H O in water made slightly acid with acetic
2 2 3 2 2 2
acid and dilute to 100 mL.
17. Procedure
17.1 Pipet 50 mL of the solution of the specimen (Section 9) into a 400-mL beaker. Add 35 mL of H SO (1+5) and 3 to 4 drops
2 4
of thymol blue indicator solution. First add NH OH (sp gr 0.90) and finally NH OH (1+10) until the color of the indicator changes
4 4
to a salmon shade intermediate between pink and yellow. This gives a pH of about 2.4. Dilute the solution to 300 mL and heat
to just under boiling. Pass in H S at a moderate rate for 40 min. Allow the precipitate to settle for 1 h and filter. Wash the filter
ten times with water saturated with hydrogen sulfide gas (H S).
17.2 Dissolve the precipitate in hot HCl (1+3) and wash the filter paper well with hot water. Boil out the H S, neutralize to
methyl orange with NH OH, and dilute to 300 mL. Add 2 g of NH Cl and 3 mL of HCl (sp gr 1.19), and heat to boiling.
4 4
17.3 Titrate the hot solution with K Fe(CN) solution (16.2),
...