Polyvinylpyrrolidone (PVP) can be conveniently fractionated from water by successive precipitation with acetone, from chloroform with ether, or from ethanol with benzene. The major part (60–70%) of the common PVP has the intrinsic viscosity of 0.12–0.30. The fractions can be liberated from the low molecular components by extraction of the solid polymer with acetone. Precipitability with ammonium sulfate is a very convenient means of characterizing the fractions. The amount of ammonium sulfate needed to produce turbidity decreases with increas...
