LETTER TO THE EDITOR 'MEASUREMENT OF CLAY SURFACE AREAS BY POLYVINYLPYRROLIDONE (PVP) SORPTION: A NEW METHOD FOR QUANTIFYING ILLITE AND SMECTITE ABUNDANCE'

Blum and Eberl (2004) presented a new technique for determining the surface area of clay minerals in sediment samples by measuring the amount of polyvinylpyrrolidone (PVP) [CAS#9003-39-8] adsorbed by a sample, and explained how the surface-area determination can be used to determine quantitatively the smectite content of the samples. In the previous method for determining surface area by PVP uptake (Blum and Eberl, 2004; also see the erratum relating to that paper published on p. 214 of the present issue), -50 mg of Na-saturated smectite was dispersed in 5 mL of water, and 1 mL of 10 wt.% PVP-55 (mean MW 55,000) was added. The sample was centrifuged, a portion of the solution decanted, and the PVP concentration in solution determined by mass after drying. The mass of PVP adsorbed on the sample was then computed by difference. This method, while accurate, had several limitations for its practical application which have now been overcome.