Preparation and standardization of 0.1 M Lithium Methoxide BP Volumetric Solution
1. PREPARATION:
Dissolve in small portions 0.694 g of Lithium in 150 ml of Anhydrous Methanol and add sufficient Toluene to produce 1000 ml.
2. STANDARDISATION:
To 10 ml of Dimethylformamide add 0.05 ml of 0.3 % w/v solution of Thymol blue in Methanol and titrate with the Lithium Methoxide solution until a pure blue colour is produced. Immediately add 0.2 gm of Benzoic acid, stir to effect solution and titrate with the Lithium Methoxide solution until the pure blue colour is restored. Protect the solution from atmospheric Carbon dioxide throughout the titration. The volume of titrant used in the second titration represents the amount of Lithium Methoxide required.
Each ml of 0.1 M Lithium Methoxide VS is equivalent to 12.21 mg of C7H6O2
Calculation:
Molarity (M) = [0.1 x Weight of Benzoic acid (in g)]/ [Titration reading (in ml) x 0.01221]
Limit: 0.1 M ± 5 % (0.0950 M – 0.1050 M)
3. STORAGE CONDITION:
Store in glass-stoppered bottles, protected from light.