Rapid complexometric determination of aluminium and total iron in silicate and other rock material

Abstract

A method is proposed for the rapid determination of aluminium and total iron that involves no prior separation of interfering elements. The sum of iron, aluminium and titanium (as the peroxy complex) is determined by complexation with trans-1,2-diaminocyclohexane-NNN′N′-tetra-acetic acid and back-titration of the excess at a pH of 3·5 to 3·7 with a copper solution, with o-dianisidine-NNN′N′-tetra-acetic acid as a metallofluorescent indicator. The iron is determined in a separate aliquot in a similar manner, but with aluminium and titanium masked with fluoride. Manganese does not interfere. The titanium present is determined spectrophotometrically, thus enabling the aluminium present to be calculated. Satisfactory agreement is obtained with existing methods for a wide range of values of both elements in rock material.