Electrodialysis of mineral silicates: an experimental study of rock-weathering (With Plate XIII.)

Palmer's investigation of the chemical and mineralogical aspects of soil-forming processes was restricted to comparative chemical analyses of the weathered shells and the essentially unaltered cores of certain spheroidal basic boulders from Wahiawa in the Hawaiian Islands. The present writer describes an experimental approach to the general problem of rock-weathering on lines suggested by Dr. A. Brammall: (a) Electrodialysis of eight typical rock-forming mineral silicates, each of which was dialysed separately after having been ground to an impalpable powder and analysed in detail. (b) Assessment of the effect of dialysis by comparing the composition of the unaltered mineral with that of the slime left in the mineral-chamber when dialysis was virtually at an end. (c) X-ray and kathode-ray tests on three of these minerals and the corresponding slimes, to ascertain whether colloidal end-products associated with, or coating, particles of unaltered mineral had integrated to form one or other of the specific ‘crystalline colloids’ identifiable in soils and clays.