Quantitative Determinations by DTA

Abstract

In the quantitative determination of minerals the problem is (after Arens) to find out a relation between any measurable DTA effect and an adequate quantity of a mineral in the heated sample being responsible for this effect. Orcel, Agafonoff and Orcel and Caillere have compared the appearence and the temperature of dehydration reactions of unknown clay samples with those of well-known samples. So they received approximate data about the portions of clay minerals in these unknown samples. Norton compared the peak heights (= ΔT) of DTA curves of unknown samples with those of calibration mixtures, but because ΔT does not only depend on the amount of a reacting substance during the heating process, but also on the chemical composition of the reacting mineral, on the disorder of the structure of this mineral and on some apparative factors (e.g. on the heating rate), this measurement of ΔT is unsuitable for quantitative measurements (Lehmann, Das and Patsch). Meanwhile only the area of a deflection in the DTA curve is regarded as a measure for the amount of a reacting substance during the heating process (Berkelhamer and Speil; Hendricks and Alexander; Kerr and Kulp; Speil et al.; Rokosz, Paulik et al. and others).