Strong Sodium Hypochlorite Solution

Definition

Strong Sodium Hypochlorite Solution is an aqueous solution of sodium hypochlorite containing not less than 8% of available chlorine. It may contain suitable stabilising agents.

Content of available chlorine, Cl

Not less than 8.0% w/w.

Total alkalinity

Not more than 1.8% w/w, calculated as NaOH, when determined by the following method. To 25 mL add 50 mL of water and 35 mL of hydrogen peroxide solution (20 vol) and titrate with 0.5m hydrochloric acid VS using methyl orange solution as indicator. Each mL of 0.5m hydrochloric acid VS is equivalent to 20 mg of NaOH. Determine the weight per mL of the solution, Appendix V G, and calculate the total alkalinity as a percentage weight in weight.

Assay

Dilute 10 mL to 250 mL with water. Add 10 mL of the resulting solution to a mixture of 50 mL of water, 1 g of potassium iodide and 12.5 mL of 2m acetic acid. Titrate with 0.1m sodium thiosulfate VS using starch solution as indicator. Each mL of 0.1m sodium thiosulfate VS is equivalent to 3.545 mg of Cl. Determine the weight per mL of the solution, Appendix V G, and calculate the percentage w/w of available chlorine.

Storage

Strong Sodium Hypochlorite Solution should be kept in a well-filled container fitted with a glass stopper or a suitable plastic cap and protected from light. It should be stored at a temperature not exceeding 20° and away from acids.