A.To about 1 g of the sample,in powder,add 20 ml of ethanol,boil in a water-bath and filter.To the filtrate,add 300 mg of decolorizing charcoal,stir and filter (solution A). To 1 ml of solution A,add 2 drops of a 2 per cent w/v solution of 3,5-dinitrobenzoic acid in methanol and 2 drops of a 5.7 per cent w/v solution of potassium hydroxide in methanol:a purplish red colour develops.