EXPLANATION
Determination of the color of petroleum products is used mainly for manufacturing control purposes and is an important quality characteristic because the color is readily observed by the user of the product. In some cases the color may serve as an indicator of the degree of refinement of the material. A variation outside the color range of a product may indicate possible contamination with another product. However, color is not always a reliable guide to product quality and should not be used indiscriminately in product specifications.
This test method covers the automatic determination of color of a wide variety of petroleum products such as undyed motor and aviation gasoline, aviation turbine fuels, napthas, kerosene, pharmaceutical white oils, diesel fuel oils, and lubricating oils. With appropriate sample handling, this test method would apply to petroleum waxes, but they were not included in the round robin, and the precision of this method with regard to waxes is unknown. This test method does not apply to solid samples, petroleum products containing dyes or having extreme fluorescence, or to cloudy samples. In the last case, the samples shall be filtered so they are clear before measuring.
This test method has one-to-one correlation for the entire range of Test Method ASTM D1500, ASTM color and for the range from 0 to +30 for Test Method ASTM D156, Saybolt color.
TEST SUMMARY
The sample is poured into a glass sample container, and the container is placed into the light path of the automatic instrument. A transmittance measurement is made in order to determine the CIE tristimulus values of the sample. These are then converted instrumentally by the appropriate algorithm to Saybolt or ASTM color values.
TEST PRECISION
Bias - There is no bias between this test method and Test Method ASTM D1500, ASTM color method. There is no bias between this test method and Test Method ASTM D156 Saybolt color method in the range from 0 to +30; however, there is bias for the range from 0 to -16.