QUANTIFICATION CURVES FOR XRD ANALYSIS OF MIXED-LAYER 14-ANGSTROM 10-ANGSTROM CLAY-MINERALS/

Using theoretical profiles of diffracted X-ray intensity for interstra tification between layers having d-spacings around 14.3 Angstrom and 1 0.1 Angstrom, a series of diagrams was derived from which the proporti on of 14.3 Angstrom layers (W-14) and the probability of passing from a 14.3 Angstrom layer to a 10.1 Angstrom layer (P-14/10) can be derive d. W-14 can be derived independently of P-14/10 using the angular dist ance between reflections situated at 18.2 degrees and 25.4 degrees 2 t heta (CuK alpha). Once W-14 is determined, P-14/10 may be obtained usi ng the angular width of the diffuse reflections between 27 degrees and 34 degrees 2 theta. In this case, two different diagrams are proposed for P-14/10 determination because experimental X-ray patterns show ei ther one or two diffuse reflections. Comparison of five experimental p atterns with theoretical patterns calculated using W-14 and P-14/10 Ob tained using these diagrams indicates that the method can be useful fo r determining W-14 and P-14/10 in unknown samples. Moreover, the metho d described is independent of the Lorentz polarization factor and the layer type. The d-spacings associated with the two kinds of layers, ho wever, should be similar (+/-1%) to those for which the determinative diagrams were calculated.