For routine grading of liquid chemical products that are clear or slightly yellow tinted, APHA Color, also called Hazen or Platinum Cobalt (Pt-Co) scale, is commonly used. The APHA color is a single-number color scale ranging from 0 (achromatic clear) to 500 (light yellow). The APHA color scale relies on visual comparison against samples. This method is subjective and difficult to maintain consistent color judgment.
Objective and consistent color measurement of chemicals can be achieved with the help of a color measuring instrument like Spectrophotometer CM-5. Comes with APHA/Hazen index and other indices and CIE Color Systems like Gardner, Iodine Color Number, CIE L*a*b* and L*C*h, the CM-5 provides a simple, fast, and comprehensive solution to chemical color measurement.