Preparation and standardization of 0.1 M Tetrabutylammonium hydroxide in 2-propanol EP Volumetric Solution
1. PREPARATION :
Dissolve 40 g of Tetrabutylammonium iodide in 90 ml of anhydrous Methanol, add 20 g of finely powdered Silver oxide and shake vigorously for 1 hour. Centrifuge a few milliliters of the mixture and test the supernatant liquid for iodides. If a positive reaction is obtained add an additional 2 g of Silver oxide and shake for a further 30 min.
Repeat this procedure until the liquid is free from iodides, filter the mixture through a fine sintered glass filter and rinse the reaction vessel and filter with three quantities, each of 50 ml of 2-propanol. Add the washings to the filtrate and dilute to 1000.0 ml with 2-propanol. Pass dry carbon dioxide free nitrogen through the solution for 5 min.
2. STANDARDISATION :
To 10 ml of Dimethylformamide add 0.05 ml of a 3 g/ l solution of Thymol blue in Methanol and Titrate with the Tetrabutylammonium hydroxide solution until a pure blue colour is obtained. Immediately add 0.200 g of benzoic acid. Stir to effect solution and titrate with the Tetrabutylammonium hydroxide solution until the pure blue colour is again obtained. Protect the solution from atmospheric carbon dioxide throughout the titration. From the volume of titrant used in the second titration ascertain the exact strength of the Tetrabutylammonium hydroxide solution. Standardize immediately before use.
1 ml of 0.1 M Tetrabutylammonium hydroxide is equivalent to 12.21 mg of C7H6O2.
3. CALCULATION :
Molarity (M) = [0.1 x Weight of Benzoic acid (in g)]/ [T.R. (in ml) x 0.01221]
T.R. = volume of 0.1 M Tetrabutylammonium hydroxide used in the second titration
4. STORAGE CONDITION :
Store in glass-stoppered bottles.
