What can Pt-Co colorimeter be used for? Liquid colorimeter，Gardner tester

A Pt-Co (Platinum-Cobalt) colorimeter, also known as the Hazen colorimeter, is an instrument used to measure the color (specifically yellowness) of liquids by comparing them to a standardized platinum-cobalt reference solution. It operates based on the Hazen scale (APHA scale) and is widely used in industries where liquid clarity and color purity are critical.

 1. Working Principle

The Pt-Co colorimeter works by:

- Comparing liquid samples against Pt-Co reference solutions (where 1 Hazen unit = 1 mg Pt/L dissolved)

- Using optical filters (typically 430 nm wavelength) to measure light absorption in yellow/brown tints.

- Quantifying color intensity with digital readouts (in Hazen/APHA units).

 5. Practical Example

Scenario: Checking pharmaceutical-grade glycerin (USP limit: ≤10 Hazen).

1. Calibrate the colorimeter using 0 Hazen (distilled water) and 100 Hazen Pt-Co standard.

2. Fill a 20 mm cuvette with glycerin.

3. Measure: Reads 8 Hazen (passes USP).

 Conclusion

The Pt-Co colorimeter is essential for quality control in water, chemicals, fuels, and pharmaceuticals, where even slight discoloration indicates impurities. Its Hazen scale provides a universal benchmark for yellowness assessment.

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