Proben-Abhängigkeit (PA) curves and simple anhydrous carbonate minerals

Marked modifications to carbonate DTA curves are caused by variations in the partial pressure of CO₂ gas in the furnace atmosphere. Calcite is used to illustrate the curve configurational changes which may occur. Attention is drawn to the effects of variations in: thermal conductivity of the gases used as furnace atmospheres, the furnace access to the ambient atmosphere, the volume of the furnace “tube“ and the size of the sample (and therefore the amount of self generated CO₂). These effects emphasise the care with which the constancy of DTA determination conditions must be maintained for content evaluation methods such as “Proben-Abhängigkeit“ curves.