To 100 ml of the resulting solution, 10
ml of 0.1 M NaOH was added diluted to 50 ml with water
and mixed thoroughly by shaking. The absorbance of the
resulting solution was measured using a UV-VIS
spectrophotometer (U. V. 2440 Double beam
spectrophotometer, SHIMADZU Corporation, JAPAN)
against a blank at 257 nm