COLOR PLATINUM-COBALT COLOR: ASTM D1209
EXPLANATION
This test method describes a procedure for the visual measurement of the color of essentially light colored liquids. It is applicable only to materials in which the color-producing bodies present have light absorption characteristics nearly identical with those of the platinum-cobalt color standards used. Sometimes this test is referred to as "APHA (American Public Health Association) Color". The petroleum industry uses the Saybolt colorimeter Test Method D 156 for measuring and defining the color of hydrocarbon solvents; however, this system of color measurement is not commonly employed outside of the petroleum industry. It has been reported by various sources that a Saybolt color of +25 is equivalent to 25 in the platinum-cobalt system or to colors produced by masses of potassium dichromate ranging between 4.8 and 5.6 mg dissolved in 1 L of distilled water. Because of the differences in the spectral characteristics of the several color systems being compared and the subjective manner in which the measurements are made, exact equivalencies are difficult to obtain.
TEST SUMMARY
One hundred mL of sample is placed in a Nessler tube. The sample is passed through a filter if it has any visible turbidity. The tube is placed in a comparator and compared with the standards.
TEST PRECISION
Repeatability: 2
Reproducibility: 7
