Differential reaction analysis (DRA); a technique for obtaining differential thermal analysis data from inert substances Available to Purchase

Many substances, including some common minerals, do not undergo thermal reactions of sufficient magnitude to provide useful differential thermal analyis data. The purpose of this study was to consider possible new techniques by which differential thermal data could be obtained from such relatively inert substances. The technique explored was to react two substances (the non-reactive material with some chemical agent) and to determine the thermal effects that occur as the mixture is heated. Several reactants were considered including alkali hydroxides, carbonates, and fluorides, microcosmic salt, V₂O₅, and Li₂WO₄. Of the reactants considered, Li₂WO₄ was found to be most satisfactory. Heating curves were obtained using heating rates of approximately 14°C per minute. Cooling curves were obtained by turning off the furnace power and the cooling rates were nonlinear.

Eight silicate minerals, wollastonite, grossular, bytownite, albite, microcline, enstatite, olivine, and zircon were studied. Differential curves for wollastonite, grossular, bytownite, albite, and microcline showed detectable reactions and characteristic differences. The reaction temperatures for enstatite, olivine, and zircon were apparently too high for the furnaces used (1000°C limit) to detect any reactions. X-ray and optical examination revealed the presence of CaWO₄, Na₂WO₄, and LiAlSiO₄ in the reaction end products. It was concluded that this method is feasible and if further developed might broaden the scope of presently existing differential thermal techniques. It is proposed that this method be called differential reaction analysis (DRA).