NEW X-RAY-DIFFRACTION METHOD OF ADDITIONS FOR CRYSTALLINE SILICA

A new method of additions is described for x-ray diffraction determina tion of trace crystalline silica. The method is derived from Klug and Alexander, X-ray Diffraction Procedures (Wiley, 1974, p. 536, Eqn. 7-1 4) and is expressed as x - sR(x)(1 - R(s))/(R(s) - R(x)) where x and s are the concentrations of analyte and spike, and R(x) and R(s) are th e relative intensities of analyte and spike. The method is particularl y attractive because the mass absorption coefficient of the matrix can be very different from silica, and large spikes can be used which min imize homogenization errors. In addition, non-zero intercepts are avoi ded. Trace determination of quartz at the < 0.1 wt.% level can be rout inely accomplished by using the new method with rotating pressed-powde r briquettes and a peak deconvolution strategy due to Wiedemann et al. [Powder Diffraction, 2 (1987a, b) 130, 137.].