As described in Section 6 of ASTM D1209, there are 2 criteria to validate a APHA/Pt-Co 500 standard:
- The APHA/Pt-Co 500 Color Standard must have a defined chemical composition and be prepared in accordance with section 6 of ASTM D1209.
- After preparation, the APHA/Pt-Co 500 standard must meet a absorbance criteria at 4 points in the blue region of the visible spectrum per Table 1 of ASTM D1209.
- Platinum-Cobalt Reference Standards
6.1 Platinum-Cobalt Stock Solution— Dissolve 1.245 g of potassium chloroplatinate (K2PtCl6) and 1.00 g of cobalt chloride (CoCl2·6H2O) in water. Carefully add 100 mL of hydrochloric acid (HCl, sp gr 1.19) and dilute to 1 L with water. The absorbance of the 500 platinum-cobalt stock solution in a cell having a 10 mm light path, with reagent water in a matched cell as the reference solution, must fall within the limits given in Table 1.
ASTM D1209 TABLE 1 Absorbance Tolerance Limits For No. 500 Platinum-Cobalt Stock Solution
|Wavelength, nm||Absorbance, A|
|430||0.110 to 0.120|
|455||0.130 to 0.145|
|480||0.105 to 0.120|
|510||0.055 to 0.065|
How to Validate a APHA/Pt-Co/Hazen 500 Color Standard
- In the Spectral Data View of EasyMatch QC, place your mouse over the view and Right Click/Configure to report Absorbance spectral data instead of Transmission. In the Spectral Data View of EasyMatch QC, place your mouse over the view and Right Click/Configure to report Absorbance spectral data instead of Transmission. If you do not have a Spectral Data View displayed, put your mouse over the Color Data Table/Right Click/Split Horizontally and Add Spectral Data View.
- Fill a 10 mm path length cell with distilled water and place on transmission bench on a HunterLab diffuse d/8 sphere instrument.
- Standardize in TTRAN LAV (Large Area of View) UV Filter in the Nominal position using the Light Blocker and 10 mm cell + DI water to set bottom and top-of-scale.
- As a PQ Performance Qualification step, read back the cell + DI water as an OQ (Operation Qualification) step. The transmission at 430, 455, 480 and 510-nm should be 100% with the corresponding absorbance being 0%.
- Read the APHA/Pt-Co 500 Liquid Color Standard to see if it reads within the absorbance tolerances at 430, 455, 480 and 510 nm in Table 1 of ASTM D1209. If your instrument only reports at 10 nm intervals. Average the absorbance at 450 and 460 nm.
If the APHA/Pt-Co/Hazen 500 Color Standard meets both the chemical and absorbance criteria of ASTM D1209, it is a 500 Standard.
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.