5. Apparatus
5.1 Colorimeter, consisting of light source, glass color standards, sample container housing with cover, and viewing piece as listed in Annex A1.
5.2 Sample Container - For referee work, use the glass sample jar as shown in Fig.1. For routine tests, it is permissible to use a cylindrical, clear glass jar with a flat bottom of 30 to 32.4mm internal diameter, 115 to 125mm in external height, and a wall thickness no greater than 1.6mm as specified in Test Method D2500, or an ordinary 125mL oil sample bottle if it meets these requirements.
6. Sampling
6.1 Samples shall be taken in accordance with the instructions in Practice D4057.
7. Diluent
7.1 Solvent Kerosine - (Warning - Combustible. Vapor harmful.) Having a color lighter than +21 Saybolt color by Test Method D156 or 1.5 by Method B of IP17, this material is used for diluting dark samples for the test. As an alternative, other solvents, such as white oil or solvent neutral 100 of satisfactory purity that meet the color requirements specified here in 7.1, are also acceptable.
NOTE 2 - Solvent kerosine complies with this requirement if it is lighter in color than potassium dichromate (K2Cr2O7) solution formed by dissolving 4.8mg of pure anhydrous K2Cr2O7 in 1L of distilled water.
8. Preparation of Sample
8.1 Liquid Petroleum Products such as Lubricating Oils - Fill the sample container to a depth of 50 mm or more and observe the color. When the sample is not clear, heat it just sufficiently enough to make it clear to perform the color measurement at that temperature. A sample heated to a temperature of 6°C(10°F) above its cloud point (see Test Method D2500) has been found suitable to test samples using this test method. When the sample is darker than 8 color, one may either stop the test and report "D8 ASTM Color" (see 10.2) or continue the test and mix 15 volumes of sample into 85 volumes of solvent kerosine or alternative material (see 7.1) and observe the color of the mixture.
8.2 Petroleum Waxes, Including Petrolatum - Heat the sample just sufficiently enough to make it fluid and clear to perform the color measurement at that temperature without heating the wax excessively, because oxidation can occur, along with consequent discoloration of the test specimen. A sample heated to a temperature of 11 to 17°C (20 to 30°F) above its congealing point, as determined in accordance with Test Method D938, has been found suitable to test samples using this test method. When the sample is darker than 8 color, one may either stop the test and report "D8 ASTM Color" (see 10.2) or continue the test and mix 15 volumes of melted sample with 85 volumes of solvent kerosine or alternative material (see 7.1) brought to the same temperature and test the mixture at that temperature.
9. Procedure
9.1 Place a sample container or containers, filled to a depth of at least 50 mm with distilled or deionized water, in the compartment or compartments of the colorimeter through which the standard glasses will be observed. Place the sample in its container in the other compartment. (When using a three-field comparator, this will be the middle compartment.) Cover the containers to exclude all exterior light.
9.2 Switch on the light source and compare the color of the sample with that of the standard glasses. When using a three-field comparator, the sample must be bracketed by darker and lighter discs or by an exact match and a darker disc.
Determine for two-field comparators which glass matches the color of the sample; or if an exact match is not possible, then use that glass which possesses the next darker color.
10. Report
10.1 Report as the color of the sample, the designation of the glass producing a matching color (for example, "7.5 ASTM Color.")
10.2 If the color of the sample is intermediate between those of two standard glasses, report that the sample is less than the darker glass designation. As an example, report the designation of the darker glass preceded by the letter "L" (for example, "L7.5 ASTM Color") or with a "<" symbol (for example, "<7.5 ASTM Color"). Never report the color as being darker than a given standard except those darker than 8 (for example, "D8 ASTM Color" or ">8 ASTM Color.")
10.2.1 If the color of the sample is less than the 0.5 glass color standard, report that the sample is less than the 0.5 glass color standard. As an example, report the designation as "L0.5 ASTM Color" or "<0.5 ASTM Color."
10.3 If the sample has been diluted in accordance with 7.1, report the color of the mixture followed by the abbreviation "Dil" (for example, "L7.5 Dil ASTM Color" or "<7.5 Dil ASTM Color"). See Note 3.
NOTE 3 - For samples that are diluted in 10.3, it is permissible for the laboratory to annotate the report in any suitable manner, provided that the information clearly conveys to the data recipient that the sample analyzed was diluted.
11. Precision and Bias
11.1 Precision - The precision of this test method as obtained by statistical examination of interlaboratory test results is as follows:
11.1.1 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following value only in one case in twenty: 0.5 color units.
11.1.2 Reproducibility - The difference between two single and independent test results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method exceed the following value only in one case in twenty: 1 color unit.
11.2 Bias - The procedure in this test method has no bias because the value of ASTM Color is subjective and can only be defined in terms of this test method.
12. Keywords
12.1 ASTM Color; color; petroleum products
