Colorimetric study of montmorillonite: effect of removal of free iron oxides in the montmorillonite - benzidine reaction

Abstract

The objective of this work is to study the influence of the iron oxide removal in the montmorillonite - benzidine reaction and the influence of the methods used for this removal. Four montmorillonites references were used and one of unknown origin. The following tests were conducted: a) soluble salts, exchangeable cations, organic matter and manganese oxide removal. b) The same treatment indicated in a and the iron oxide remoral by the method of JEFFRIES & JACKSON) (1949). c) The same treatment indicated in a and the iron oxide removal by a dithionite - citrate system buffered with sodium bicarbonate. There was influence of the type of treatment for all montomorillonites tested. The iron oxides removal seemed to make uniform the color obtained and the velocity of reaction. The free-H method gave the best results either for the color uniformization or the intensity of the color.