A: Ultraviolet Absorption 197U—

B: Dissolve about 400 mg in 10 mL of water, add 1 mL of 3 N hydrochloric acid, filter, and wash the precipitate with two 5-mL portions of cold water. Recrystallize from alcohol the precipitate so obtained, and dry at 110 for 1 hour: the p-aminobenzoic acid so obtained melts between 186 and 189.

C: A solution (1 in 100) meets the requirements of the flame test for Sodium 191.

Standard solution— Dissolve 10 mg of p-toluidine in 5 mL of methanol in a 100-mL volumetric flask, dilute with water to volume, and mix. Transfer 1 mL to a 100-mL volumetric flask, dilute with water to volume, and mix.

Test solution— Transfer 5.0 g of Aminobenzoate Sodium to a suitable flask, and add a volume of 1.25 N sodium hydroxide that is just sufficient to dissolve the test specimen and to render the solution just alkaline to phenolphthalein TS. Dilute with water to 50 mL, and steam-distill the solution, collecting about 95 mL of the distillate in a 100-mL volumetric flask. Dilute with water to volume, and mix.

Procedure— Transfer 20.0-mL portions of the Standard solution and the Test solution to separate 100-mL beakers, and transfer 20.0 mL of water to a third 100-mL beaker to provide the blank. Treat each as follows. Add 5.0 mL of 1 N hydrochloric acid, and cool in an ice bath. Add 2.0 mL of 0.1 M sodium nitrite dropwise, with stirring, allow to stand for 5 minutes for the diazotization reaction to be complete, add quickly to 10.0 mL of a cold solution of guaiacol (freshly prepared by dissolving 0.20 g of guaiacol in 100 mL of 1 N sodium hydroxide), mix, and allow to stand for 30 minutes. Concomitantly determine the absorbances of the solutions at the wavelength of maximum absorbance at about 405 nm, with a suitable spectrophotometer, using the blank to set the instrument: the absorbance of the solution obtained from the Test solution does not exceed that of the solution obtained from the Standard solution, corresponding to not more than 0.002% of volatile diazotizable substances, as p-toluidine.