Adsorption of Methylene Blue by High-Silica Sands

Abstract

HIGH-SILICA sands from which the intergranular material has been washed away have been found to adsorb considerably more methylene blue per unit of superficial surface as determined by the air permeability method¹ than was adsorbed by crushed quartz crystal. A sample of the latter material (from B.D.H.) took up 1.2 × 10⁻⁴ mgm. of dye per sq. cm. superficial surface, and this figure agrees well enough with that calculated by Gaudin and Rizo Patròn² for the adsorptive capacity of a quartz surface for positive ions to suggest that the surface accessible to methylene blue was very nearly the same in extent as the superficial surface for this material. The same was not true of most sand samples. Values for the surface accessible to methylene blue calculated from the figure obtained for crystal quartz were found in some instances to be many times the superficial surface.