ASTM D5386 Test Method for Color of Liquids Using Tristimulus Colorimetry
3. Summary of Test Method
3.1 Color is measured by tristimulus values of light transmitted by a sample as percent of light transmitted by distilled water. Convert the measured tristimulus values by appropriate equations to the platinum-cobalt scale.
4. Significance and Use
4.1 The major objective of the visual platinum-cobalt (Pt-Co) method of color measurement, as defined in Test Method D1209, is to rate specific materials for yellowness. This yellowness is frequently the result of the undesirable tendency of liquid hydrocarbons to absorb blue light due to contamination in processing, storage or shipping.
4.2 Clear liquids can be rated for light absorbing yellowish or brownish contaminants, using scales that simulate the long-established visual-comparison method just cited. Where needed, dimensions of color can be reported to identify any pinkness or greenness (one dimension), or grayness.
