Preparation and standardization of 0.05 M Potassium Hydroxide EP Volumetric Solution
1. PREPARATION :
Dissolve 3 g of Potassium hydroxide in sufficient carbon dioxide free water to produce 1000 mL.
2. STANDARDISATION :
Titrate 20 mL of the Potassium hydroxide solution with 0.05 M Hydrochloric acid using 0.5 mL Phenolphthalein as indicator.
3. CALCULATION :
Molarity (M) = [Titration Reading (in mL) x Exact Molarity of 0.05 M HCL]/20
4. PREPARATION OF INDICATORS / REAGENTS :
a. 0.05 M Hydrochloric acid VS :
Preparation and standardisation as per respactive procedure.
b. Phenolphthalein solution :
Dissolve 0.1 g Phenolphthalein in 80 mL of Ethanol (96%) and dilute to 100 mL with water.
Test for sensitivity : To 0.1 mL of the Phenolphthalein solution add 100 mL of carbon dioxide free water. The solution is colourless. Not more than 0.2 mL of 0.02 M Sodium hydroxide is required to change the colour to pink.
Colour change : pH 8.20 (colourless) to pH 10.00 (red).
5. STORAGE CONDITION :
Store in glass-stoppered bottles.