Preparation and standardization of 0.1 M Tetrabutylammonium Hydroxide

1.0          Scope:

1.1                   The procedure is applicable to preparation and standardization of 0.1 M

Tetrabutylammonium Hydroxide.

2.0          Apparatus:

2.1        Analytical balance.

2.2        50 ml burette (0.1 ml graduated).

2.3        250 ml stoppered conical flasks.

2.4        1000 ml volumetric flask.

2.5        100 ml measuring cylinder.

2.6        Ice-Bath.

       (Use Class 'A' glassware)

3.0          Reagents:

3.1        Tetrabutylammonium iodide.

3.2        Silver Oxide (Powdered).

3.3        Benzoic acid (AR.Grade).

3.4        Dimethylfomamide

3.5        Thymol blue.

3.6        Dehydrated Methanol.

3.7        Dehydrated Toluene.

4.0                Procedure:

4.1               Preparation of Solution:

Dissolve 40g of tetrabutylammonium iodide in 90 ml of dehydrated methanol in a glass-stoppered flask. Place in an ice-bath, add 20 g of powdered silver oxide, insert the stopper and agitate vigorously for 1 hour. Centrifuge a few ml, and test the supernatant liquid for iodides. (Test for iodides: To 1 ml of this solution add 0.5 ml of mercuric chloride solution; if a dark red precipitate is formed it shows positive test for iodide). If the test is positive, add an additional 2 g of silver oxide and continue to stand for 30 minutes with intermittent agitation. When all of the iodide has reacted, filter through fine sintered-glass filer. Rinse the flask and filter with three quantities, each of 50 ml, of anhydrous toluene. Add the washings of the filtrate and dilute to 1000ml with anhydrous toluene. Flush the solution for 10 minutes with dry, carbon

 dioxide-free nitrogen. Store protected from carbon dioxide and moisture.

4.2               Standardization:                                                Molarity Limit: + 10% (0.0900 to 0.1100)

Weigh accurately about 0.4 g of benzoic acid, dissolve in 80 ml of dimethylformamide, add a few drops of a 1 per cent w/v solution of thymol blue in dimethylformamide and titrate with the tetrabutylammonium hydroxide solution to a blue end-point. Protect the solution from atmospheric carbon dioxide throughout the titration. Perform a blank determination and make any necessary correction.

Perform standardization in triplicate.

The % of RSD limit not more than 2.0.

1 ml of 0.1 M tetrabutylammonium hydroxide is equivalent to 0.01221 g of C₇H₆O₂.

                                         Wt of Benzoic acid (g) x 0.1

M = ----------------------------------------------------------------------------------------------

          0.01221 x Titre volume (ml) of 0.1 M Tetrabutylammonium hydroxide.

5.0               Storage:

                    Store below 25°C & store in amber coloured bottle. Protect exposure from CO₂   & water.

6.0               Shelf life:

6.1               Shelf life of above solution shall be one month from the date of preparation

6.2               Restandaridize the above solution daily before use.

                    NOTE: Discard the volumetric solution whenever sedimentation, crystallization or fiber         particles observed in the reagent bottle.

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