Carbonate mineral detection by variable atmosphere differential thermal analysis

Abstract

GREATLY improved detection limits for the presence of anhydrous carbonate minerals in mixtures with other types of minerals can be obtained by variable atmosphere differential thermal analysis (DTA) using dynamic furnace atmospheres of CO₂ (flow rate 100 ml min⁻¹)¹. Details will be published elsewhere^2,3 (see ref. 1 for details of the Du Pont unit and conditions of analysis). These carbonates fall into two groups; those which decompose in CO₂ with single, or multiple⁴ endothermic dissociation reactions liberating CO₂. The first group contains, calcite CaCO₃, magnesite MgCO₃, smithsonite ZnCO₃, and siderite FeCO₃ (ref. 5); while the second includes dolomite CaMg(CO₃)₂, ankerite Ca(MgFe)(CO₃)₂ and cerussite PbCO₃ (ref. 4). Here calcite and dolomite are taken as typical examples and their behaviour described.