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How to Prepare a Standard for Free Chlorine Analysis

Preparation of a standard solution for free chlorine

Reagents:

Cat.No. 100316  Hydrochloric acid 25 % for analysis
Cat.No. 105614  Sodium hypochlorite solution (6 - 14 % active chlorine)

Preparation of a stock solution of free chlorine:

First prepare a 1:10 dilution using a sodium hypochlorite solution containing approximately 6 - 14 % of active chlorine. 

Precise assay of the stock solution for free chlorine: Pipette 10.0 mL of the stock solution into a 250-mL ground-glass-stoppered conical flask containing 60 mL of water for analysis. 

Calculation:

1 mL sodium thiosulfate solution = 3.55 mg free chlorine