Sodium Hydroxide VS

Sodium Hydroxide VS NaOH = 40.00

For a 0.1m solution Dissolve 4.2 g of sodium hydroxide in sufficient carbon dioxide-free water to produce 1000 mL.

Ascertain its exact concentration immediately before use in the following manner. Titrate 20 mL of the solution with 0.1m hydrochloric acid VS using the indicator prescribed in the assay in which the solution is to be used. Each mL of 0.1m hydrochloric acid VS is equivalent to 4.00 mg of NaOH.

When a carbonate-free solution is specified it is prepared using the following method. Dissolve sodium hydroxide in an equal weight of water and allow to stand overnight. Taking precautions to avoid absorption of carbon dioxide, siphon off or decant the clear supernatant liquid and dilute with carbon dioxide-free water to the desired molarity. The solution complies with the following test.

Titrate 20 mL of hydrochloric acid VS of the same molarity as the solution being examined with the sodium hydroxide solution using 0.5 mL of phenolphthalein solution as indicator. At the end point add just sufficient of the acid to discharge the pink colour and boil to reduce the volume to 20 mL. Add, whilst boiling, sufficient of the acid again to discharge the pink colour which does not reappear after prolonged boiling. Not more than 0.1 mL of the acid is required.

For a 1m solution Dissolve 42 g of sodium hydroxide in sufficient carbon dioxide-free water to produce 1000 mL.

Ascertain its exact concentration immediately before use in the following manner. Titrate 20 mL of the solution with 1m hydrochloric acid VS using the indicator prescribed in the assay in which the solution is to be used. Each mL of 1m hydrochloric acid VS is equivalent to 40.00 mg of NaOH.

When 0.1m sodium hydroxide VS is used in the assay of halide salts of organic bases, ascertain its exact concentration in the following manner. Dissolve 0.100 g of benzoic acid in a mixture of 5 mL of 0.01m hydrochloric acid and 50 mL of ethanol (96%). Titrate with the solution being examined and note the volume added between the two points of inflection. Each mL of 0.1m sodium hydroxide VS is equivalent to 12.21 mg of C₇H₆O.