ISO 2211 method 1973 – Liquid Chemical Products – Measurement of Colour in Hazen Units (Platinum Cobalt Scale)
The color of liquids may be an indication of their identity, purity or degree of refinement. This method determines the color of clear liquids using the APHA Color scale (Platinum/Cobalt Color Scale or the Hazen Color Scale) which measures the color of transparent liquids, differentiating between shades of pale yellow in nearly colorless samples. The scale runs from 0 to 500 hundred with 0 being distilled water.
Colored standard solutions are prepared. The sample color is compared to the standard solutions and the color that most closely matches the sample is reported.