1. Sulfuric acid, concentrated, A.R. grade or equivalent
2. Catalysts: Mixture of Potassium sulfate (CuSO4.5H2O) and copper sulfate (K2SO4) in
the ratio of 10:1 or without selenium (IV) dioxide
3. Sodium hydroxide solution, 32%.
Note: The reaction of NaOH with water is exothermic. Place reaction vessel in a basin of ice
cold water when dissolving it.
4. Hydrochloric acid, 0.1 N standard solution. Pipette 8.3 mL of concentrated
hydrochloric acid to approximately 500 mL distilled H2O in 1 L volumetric flask soaked in ice
cold water. Allow to cool and make up to volume with distilled H2O. Pour the solution in 1 L
brown bottle and let the solution stand for 2 or 3 days with occasional shaking before
standardisation.
5. Standardisation of HCl solution stated in No.4. Weigh accurately about 0.47 g AR
sodium tetraborate decahydrate (borax) into a 250mL conical flask, dissolve in about 50mL
water and add a few drops of methyl red indicator solution. Titrate with the hydrochloric acid
from a burette until the colour changes to pink at the endpoint. [Methyl red indicator solution:
dissolve about 1g of methyl red in 600mL alcohol and dilute with 400 mL water.]
Normality = wt borax (g) x 1000 mLs HCl titrant x 190.72
6. Methyl red/bromcresol green indicator solution. (20 mg methyl red + 100 mg
bromcresol green in 100 ml ethanol)
7. Boric acid solution, 2%.