GB/T 6909-2018 in English

Standardized interpretation of boiler water and cooling water hardness determination

1. Standard background and technical evolution analysis

GB/T 6909-2018 "Boiler water and cooling water analysis method hardness determination" is a national standard of the People's Republic of China, which is used to regulate the test method of hardness in boiler water and cooling water. This standard replaces the previous GB/T 6909-2008 version and has made many technical improvements.

2. Comparative analysis of standard frameworks

3. Detailed explanation of the determination method

Eriochrome Black T Method

This method uses eochrome black T indicator in an alkaline environment and uses ethylenediaminetetraacetic acid disodium (EDTA) standard titration solution to react with Ca²⁺ and Mg²⁺, and the end point changes from red to pure blue. It is applicable to water samples with a hardness range of 0.01 mmol/L to 5 mmol/L.

Acid Chrome Blue K Method

Acid Chrome Blue K indicator is used under alkaline conditions to convert hardness into micromolar concentration through titration reaction. It is applicable to the range of 1 µmol/L to 100 µmol/L.

Potentiometric titration

Using an automatic potentiometric titrator and a calcium ion electrode, hardness determination is achieved through chemical metrological point identification. This method has high accuracy and is particularly suitable for complex water quality samples.

4. Implementation recommendations