A: Dissolve about 0.1g in 5mLof sulfuric acid:an orange or brown-red color is produced.

B: The visible absorption spectrum of a portion of the Assay preparationemployed for measurement of absorbance in the Assayexhibits maxima at the same wavelengths as that of a similar solution of USP Gentian Violet RS,concomitantly measured.

Standard preparation— Transfer an accurately weighed quantity of USP Gentian Violet RS,equivalent to about 13.5mg of anhydrous gentian violet,to a 100-mLvolumetric flask.Add 50mLof hydrochloric acid,and mix until dissolved.Dilute with hydrochloric acid to volume,and mix.Pipet 5mLof the solution into a 50-mLvolumetric flask,add hydrochloric acid to volume,and mix.

Assay preparation— Transfer about 500mg of Cream,accurately weighed,to a 100-mLvolumetric flask.Add 15mLof hydrochloric acid,warm in a water bath to disperse the cream thoroughly,cool,add hydrochloric acid to volume,and mix.Filter the mixture through a fine-porosity,sintered-glass filter.Pipet 2mLof the solution into a 10-mLvolumetric flask,add hydrochloric acid to volume,and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationin 1-cm cells at the wavelength of maximum absorbance at about 435nm,with a suitable spectrophotometer,using hydrochloric acid as the blank.[NOTE—Use quartz cells having tightly fitting covers to prevent corrosion caused by the hydrochloric acid.]Calculate the quantity,in mg,of C25H30ClN3in the portion of Cream taken by the formula: in which Cis the concentration,in µg per mL,of USP Gentian Violet RS,calculated on the anhydrous basis,in the Standard preparation;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.