Method of Analysis for Sodium Hydroxide

1. Description

White, crystalline masses supplied as sticks, pellets or slabs; deliquescent.

2. Solubility

Very soluble in water; freely soluble in ethanol (95%).

3. Assay

Limit: NLT 97.0 % & NMT 100.5 %.
Reagent required
Phenolphthalein
Methyl orange
1M Hydrochloric acid
Procedure: Weigh accurately about 2 g, dissolve in about 80 ml of carbon dioxide-free water, add 0.3 ml of phenolphthalein solution and titrate with 1M hydrochloric acid. Add 0.3 ml of methyl orange solution and continue the titration with 1M hydrochloric acid. Each ml of 1M hydrochloric acid used in the second part of the titration is equivalent to 0.1060 g of Na₂CO₃. Each ml of 1M hydrochloric acid used in the combined titrations is equivalent to 0.0400 g of total alkali, calculated as NaOH.
Calculation
                                             Total B.R. X Molarity X 0.04X100
% of Sodium Hydroxide = ------------------------------------------
                                                    Wt. Taken in gm X 1.0