SIMULTANEOUS DETERMINATION OF MAJOR CONSTITUENTS AND IMPURITIES IN HIGH-PURITY MULLITE USING PRESSURE ACID DECOMPOSITION

A simple, precise and sensitive method is described for the simultaneous determination of major constituents (Al2O3 and SiO2) and impurities (Ca, Cr, Fe, K, Li, Mg, Mn, Na, Sr, Ti, V, Y, Zn and Zr) in high-purity mullite (3Al2O3.2SiO2). A 0.5 g amount of the powder sample was decomposed with 5 ml of H2SO4 (1+2) at 230-degrees-C for 16 h in a polytetrafluoroethylene pressure vessel. The decomposed mixture was separated to a solution and a precipitate by filtration. After the solution was diluted to a constant volume with water, inductively coupled plasma atomic emission spectrometric analysis for the impurity elements and conventional volumetric analysis for Al2O3 were carried out. The precipitate was a shed in a platinum crucible and gravimetric analysis for SiO2 was carried out. The proposed method was successfully applied to the simultaneous determination of Al2O3, SiO2 and the impurities in commercial mullite samples. The analytical results were in good agreement with those obtained by other methods. This method has advantages in simplicity, good precision and high sensitivity for the comprehensive analysis of high-purity mullite.