Identification—
A:
Digest a quantity of powdered Tablets, equivalent to about 1 g of sodium salicylate, with 20 mL of water, and filter: the filtrate responds to the flame test for
Sodium 
191
and to the tests for
Salicylate 191.
B:
To 10 mL of the filtrate obtained in
Identification test
A add a slight excess of 3 N hydrochloric acid, collect the precipitate on a filter, wash it with small portions of cold water until the last washing is free from chloride, and dry at about 105
for 1 hour: the salicylic acid so obtained melts between 158
and 161
(see
Melting Range or Temperature 741).
Dissolution 711—
Medium:
water; 900 mL.
Apparatus 1:
100 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of C7H5NaO3 dissolved from UV absorbances at the wavelength of maximum absorbance at about 266 nm, using filtered portions of the solution under test, diluted with water, if necessary, in comparison with a Standard solution having a known concentration of Sodium Salicylate in the same medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of C7H5NaO3 is dissolved in 45 minutes.
Assay—
Place not less than 20 Tablets in a 200-mL volumetric flask, add 100 mL of water, and allow to stand, with frequent agitation, until the tablets disintegrate completely. Dilute with water to volume, and mix. Filter through a dry filter into a dry flask, discarding the first 10 mL of the filtrate. Transfer an accurately measured volume of the subsequent filtrate, equivalent to about 500 mg of sodium salicylate, to a separator, and dilute with water, if necessary, to make about 25 mL. Add 75 mL of ether and 10 drops of
bromophenol blue TS, and titrate with 0.1 N hydrochloric acid VS, mixing the water and ether layers by vigorous shaking until a permanent, pale green color is produced in the water layer. Draw off the water layer into a small flask, wash the ether layer once with 5 mL of water, and add this to the water layer. Add 20 mL of ether to the combined water solutions, and mix. Continue the titration with vigorous shaking until a permanent, pale green color is produced in the water layer. Each mL of 0.1 N hydrochloric acid is equivalent to 16.01 mg of C
7H
5NaO
3.
