STUDIES ON THE ESTIMATION OF PANS——Ⅱ.ESTIMATION OF PANS BY NONAQUEOUS SOLVENTS TITRATION

A diazotization back titration method for estimation of PANS was proposed in a previous paper,but it is lack of accuracy and time-consuming.In this paper,a nonaqueous solvents titration method is proposed,which is more rapid,accurate and convenient than the diazotization method.The procedure is suggested as follows: Weigh accurately 0.3 to 0.4 gm.of sample in a 50 ml.beaker and dissolve in 20 ml.of pyridine or benzene-methanol.The beaker is covered with a cardboard provided with a small hole for the buret tip.Titrate with 0.1 sodium methoxide to a clear blue color using thymol blue as in- dicator.During the titration the solution is agitated by means of a magnetic stirrer.Each ml. of 0.1 N sodium methoxide solution is equivalent to 44.66 mg.PANS. The solvents employed contain some acidic impurities and should therefore be neutralized with sodium methoxide immediately before using.