Ricca Chemical APHA-Hazen Color Standards, Platinum-Cobalt

Ricca Chemical Platinum-Cobalt APHA-Hazen Color Standards are also known as "Hazen" color standards because the colorimetric scale was developed by Allen Hazen for the APHA. The APHA defined the use of this color scale during the 1890's. The color scale was developed to serve as a visual indicator of waste water purity whereby a faintly yellow color is present due to the presence of leachates of organic mater such as roots, bark, leaves, peat or humus.

ASTM D1209 Standard Test Method for Color of Clear Liquids (a.k.a. "Platinum-Cobalt Scale") defines the color scale as the visual yellowness present within a liquid sample based on a chemical reagent standard solution. The APHA Platinum-Cobalt Hazen color scale as it relates to the instrumental method is better defined in ASTM D5386 Standard Test Method for Color of Liquids Using Tristimulus Colorimetry. This scale is a singular numeric value of low chroma yellowness which is metric based on the dilution of a potassium chloroplatinate reagent stock solution. An (APHA) unit is constituted on a volume dilution of 500 parts of the platinum-cobalt (Pt-Co) reagent stock solution per million parts of DI Water (distilled water). DI Water is rated with an APHA/Pt-CO value of "0" while the APHA Platinum-Cobalt-Hazen reagent stock solution provides a value of 500 APHA/Pt-Co/Hazen. (Reference: Section 6 - ASTM D1209).

In modern chemistry labs, the APHA Platinum-Cobalt-Hazen color scale and methodology is used as a standard of purity in multiple industries including petrochemical manufacturing, pharmaceutical manufacturing, plastics manufacturing and many other industries. The appearance of yellowness in a sample provides a visual indicator of many of the adverse affects of many manufacturing processes such as exposure to heat, light, aging or any other degrading element introduced to the sample or process.