FAQ: ” We are currently using a 10 mm path length and read in the 0 – 50 region for APHA/Pt-Co/Hazen Color, usually in the area of 10. Would you recommend a 10 mm path length with our equipment for this application?”
“APHA Color” is also known by two other names – “Pt-Co Color” and “Hazen units (HU)”. All three names represent the same color scale. As the APHA/Pt-Co/Hazen Color is dependent on the path length or thickness of the sample, it is important to:
- Use the same cell path length for all measurements.
- Report the cell path length as part of the measurement method if inter-instrument agreement of APHA/PtCo/Hazen Color values is important at multiple sites.
HunterLab’s instrument correlation to the visual APHA/Pt-Co/Hazen Color scale per ASTM D5386 allows the user to select a 10-mm, 20-mm or 50-mm path length cell by configuring the Color Data View in EasyMatch QC software to display “APHA-10mm”, “APHA-20mm” or “APHA-50mm”.
While any of these three cell path lengths can be used to effectively measure APHA/Pt-Co/Hazen Color, the optimal choice for cell path length choice is based on the following criteria:
- A 10-mm path length cell is typically used for highly saturated or chromatic liquids, typically with APHA/Pt-Co/Hazen Color values > 300.
- The easy-to-fill 20-mm path length cell is used for moderately chromatic liquids, and is the default cell path length when a wide APHA/Pt-Co/Hazen Color range of liquid colors is being measured from 0 (distilled water) to 500.
- The longer 50-mm path length cell is preferred for clear or near clear liquids where APHA/Pt-Co/Hazen Color values < 30, and especially when APHA < 10.
Mr. Philips has spent the last 30 years in product development and management, technical sales, marketing, and business development in several industries. Today, he is the global market development manager for HunterLab, focused on understanding customer needs, providing appropriate solutions and education, and helping to solve customer color challenges across these industries and cultures.