where Wx (A) is the weight of element or compound A in the xth sample, K is a parameter which relates the intensity ratio I of a diffraction peak to the weight ratio, Ii (A) and Ij (C) are the intensity ratios of the diffraction peaks for the elements or compounds A and C and ??i (A) and ??j (C) are the Bragg angles for the element or compounds A and C, respectively.