Description
Technical Bulletin
This standard is issued under the fixed designation D 848; 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.
This standard has been approved for use by agencies of the Department of Defense.
1.Scope
- This test method covers the determination of the acid wash color of benzene, toluene, xylenes, refined solvent naphthas, and similar industrial aromatic hydrocarbons.
- 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. For specific hazard statements, see Section 8 and Note 1.
2. Referenced Documents
2.1 ASTM Standards:
D 1193 Specification for Reagent Water2
D 3437 Practice for Sampling and Handling Liquid Cyclic
Products3
D 4790 Terminology of Aromatic Hydrocarbons and Related
Chemicals3
2.2 Other Document:
OSHA Regulations. 29 CFR, paragraphs 1910.1000 and
1910.12004
3. Terminology
3.1 See Terminology D 4790 for definitions of terms used in this test method.
4. Summary of Test Method
4.1 A mixture of the aromatic hydrocarbon and sulfuric acid is vigorously shaken and the color of the acid layer is compared with that of color standards prepared from CoCl2 and FeCl3.
5. Significance and Use
5.1 This test method is suitable for setting specifications on the materials referenced in 1.1. It may also be used as an internal quality control tool and in development or research work.
5.2 The color developed in the acid layer gives an indication of impurities which if sulfonated would cause the material to be discolored.
6. Apparatus
6.1 Containers for Color Standards—Clear and unblemished,clean, French square, flint-glass, flat-bottom, glassstoppered,1-oz capacity bottles holding 31 to 33 mL when filled to the neck. The bottles shall be numbered consecutively from 0 to 14.
6.2 Test Containers—Containers exactly like those described in 6.1 except that each French square bottle shall be marked by etching to show when the bottle contains the volume of 7 and 28 mL, respectively. Colored crayons and similar markers shall not be used for marking the bottles.
7. Reagents
7.1 Purity of Reagents—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 available.5 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.
7.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean distilled water, Type I or II as described in Specification D 1193.
7.3 Cobalt Chloride (CoCl2· 6H2O).
7.4 Ferric Chloride (FeCl3· 6H2O).
7.5 Hydrochloric Acid (1 + 39)—Mix 25 mL of hydrochloric acid (31 weight % HCl) with 975 mL of water.
7.6 Potassium Chromate (K2CrO4).
7.7 Potassium Dichromate (K2Cr2O7).
7.8 Sulfuric Acid (96 6 0.5 weight % H2SO4).
7.9 Sulfuric Acid (78 6 0.5 weight % H2SO4).
This test method is under the jurisdiction of ASTM Committee D-16 on Aromatic Hydrocarbons and Related Chemicals and is the direct responsibility of Subcommittee D16.0A on Benzene, Toluene, Xylenes, Cyclohexane, and Their Derivatives.
Current edition approved June 10, 1997. Published September 1997. Originally published as D 848 – 45. Last previous edition D 848 – 93.
Annual Book of ASTM Standards, Vol 11.01.
Annual Book of ASTM Standards, Vol 06.04.
Available from Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402.
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.
8. Hazards
8.1 Consult current OSHA regulations, supplier’s Material Safety Data Sheets, and local regulations for all materials used in this test method.
8.2 When handling strong acids or acid cleaning solutions,wear proper personnel protective equipment.
9. Sampling
9.1 Sample the material in accordance with Practice D 3437.
10. Cleaning of Containers
10.1 Clean the containers (Section 6) with a cleaning solution that will not impact the results, such as a chromatic acid substitute, rinse with tap water followed by distilled water,and dry in an oven set at a minimum of 105°C for at least 1 h. Likewise, clean all other glassware used in this test method.
11. Preparation of Reference Color Standards
11.1 Stock Solutions—Prepare the following basic reagent solutions for use in preparing the reference color standards:
11.1.1 Solution A—Dissolve 59.50 g of CoCl2·6H2O in HCl
(1 + 39) and make up to 1 L in a volumetric flask with HCl(1 + 39).
11.1.2 Solution B—Dissolve 45.054 g of FeCl3·6H2O in HCl (1 + 39) and make up to 1 L in a volumetric flask with HCl (1 + 39).
11.1.3 Solution C—Mix 31⁄2 volumes of Solution A with 361⁄2 volumes of Solution B and dilute with 90 volumes of water.
11.1.4 Solution D—Mix 31⁄2 volumes of Solution A with 361⁄2 volumes of Solution B.
11.1.5 Solution E—Prepare an aqueous solution of K2CrO4 saturated at 21°C.
11.1.6 Solution F—Prepare an aqueous solution of K2Cr2O7 saturated at 21°C and dilute with an equal volume of water.
11.2 Prepare reference color standard solutions having the following compositions and numbered from 0 to 14:
No. 0—Distilled water.
No. 1—1 volume of Solution C plus 1 volume of water.
No. 2—51⁄2 volumes of Solution C plus 2 volumes of water.
No. 3—Solution C.
No. 4—1 volume of Solution D plus 1 volume of water.
No. 5—51⁄2 volumes of Solution D plus 2 volumes of water.
No. 6—Solution D.
No. 7—5 volumes of Solution E plus 2 volumes of water.
No. 8—Solution E.
No. 9—7 volumes of Solution E plus 1⁄2 volume of Solution F.
No. 10—61⁄2 volumes of Solution E plus 1 volume of Solution F.
No. 11—51⁄2 volumes of Solution E plus 2 volumes of Solution F.
No. 12—1 volume of Solution E plus 1 volume of Solution F.
No. 13—2 volumes of Solution E plus 5 volumes of Solution F.
No. 14—Solution F.
11.3 Rinse the No. 0 container (5.1) and its glass stopper three times with water, fill with water, and stopper. Rinse the No. 1 container and its stopper three times with reference color standard solution No. 1 (Section 11.2), fill with this solution, and stopper. In this way, prepare the set of containers of color standards from 0 through 14 having the compositions shown for the corresponding color solution standards in 11.2. When filling the French square bottles, leave 1⁄4 in. (6 mm) of vapor space below the neck of the bottle. Seal each container with paraffin to prevent loss by evaporation or seepage.
12. Procedure
12.1 Rinse a test container (5.2) twice with acid of the strength specified in Table 1 for the type of sample to be tested (Note 1). Drain the rinsings and fill with the acid up to the 7-mL mark. Add sufficient sample to bring the total volume to the 28-mL mark (Note 2). Insert the stopper, hold a finger over the stopper, and give vigorous shakes with a stroke of 13 to 25 cm (5 to 10 in.), shaking for a total of 150 cycles over a period
of 40 to 50 s, that is at a rate of 3 to 3.75 cycles/s.
NOTE 1—Precaution: Concentrated sulfuric acid will cause severe burns on contact with the skin. As a precaution the test container should
be wrapped in a towel or enclosed in a plastic bag during the shaking period.
NOTE 2—If the room temperature is above 85°F, maintain the acid, sample, and reference color standards at a temperature between 77 and
85°F (25 and 29°C) through the test, and insulate the test container in some convenient way, such as wrapping with a cloth, during the shaking
period.
12.2 Allow the container to stand, protected from direct sunlight, for the period of time shown in Table 1. Without further delay, invert the container gently once or twice to obtain a uniform color in the acid layer, and compare the color of the acid layer with that of the standards (10.3). Make the
comparison against a white background or against daylight,using transmitted light (Note 3). When testing samples in Group 1 (Table 1), observe the color of the oil layer as well as that of the acid layer.
NOTE 3—Agreement of results may be improved by using a color comparator of a suitable type for observing the color of the acid layer in
comparison with the reference standard color solution.
12.3 Designate the color of the acid layer by the number of the nearest matching standard, following the number with a plus or minus sign if the sample is darker or lighter, respectively,than the standard. Disregard any difference in hue and determine only whether the color of the acid layer is darker or lighter than the color of the reference standard to which the sample most nearly corresponds. If the hue of the acid color is
different from the hue of the reference color standard, record the color number followed by (X). Thus “No. 4 − (X)” means that the acid wash test color is slightly lighter than No. 4 color standard and that the hue of the No. 4 color standard is not the same as the hue of the acid layer.
TABLE 1 Acid Strengths and Standing Times
| Sample | Acid Strength,% | Standing Time,min | |
| Group 1 |
Benzene, all ASTM grades Toluene, all ASTM grades Xylene, nitration grade Xylene, 5° Xylene, 10° Any other more highly refined products |
96 | 15 |
| Group 2 |
Xylene, industrial grade Refined solvent naphtha |
96 | 5 |
| Group 3 |
Hi-flash solvent Heavy solvent naphtha |
78 | 5 |
13. Interpretation of Results
13.1 Report Group 1 samples (Table 1) as passing the test only when the oil layer shows no change in color and when the acid layer is not darker than the specified color standard. A cloudiness or haze in the oil layer should not be interpreted as a change in color.
13.2 When testing samples of Groups 2 or 3, disregard the color of the oil layer and report the sample as passing the test when the acid layer is not darker than the specified color standard.
14. Precision and Bias
14.1 Precision data have not been established for all types of samples on which this test method is used. Limited cooperative tests were conducted in 1961, principally to establish equality with the previously used shaking procedure. Precision estimates taken from these data are as follows:
| Repeatability | Repeatability | Reproducibility | Reproducibility | ||
|
Average Acid Wash Color |
Degrees of Freedom |
95% Repeatability |
Degrees of Freedom |
95% Reproducibility | |
| Benzene |
1.4 6.1 |
11 12 |
0.75 1.85 |
9 10 |
2.34 4.47 |
| Xylene |
4.7 10.2 |
12 12 |
0.40 1.14 |
10 10 |
1.39 |
15. Keywords
15.1 acid wash color; aromatic hydrocarbons
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