Preparation and standardization of 0.5 M Sodium Hydroxide EP Volumetric Solution
Dissolve 21 g of Sodium hydroxide in carbon dioxide free water and dilute to 1000 mL with the same solvent.
Dissolve 0.75 g of Potassium hydrogen phthalate in 50 mL of water. Titrate with the Sodium hydroxide solution, determining the end point Potentiometrically or using 0.1 mL of Phenolphthalein solution as indicator.
1 mL of 0.5 M Sodium hydroxide is equivalent to 102.1 mg of C8H5KO4.
Molarity (M) = [0.5 x Weight of Potassium hydrogen phthalate (in g)]/[0.1021 x Titration reading (in mL)]
Limit: 0.5 M ± 5 % (0.4750 M – 0.5250 M)
3. PREPARATION OF INDICATORS / REAGENTS:
a. Phenolphthalein solution :
Dissolve 0.1 g of Phenolphthalein in 80 mL of Ethanol (96 %) and dilute to 100 mL with water.
4. STORAGE CONDITION:
Store in glass stoppered bottles.