AbstractThe commonly used equation relating the intensity of characteristic X‐radiation to the concentration of the element to be determined contains three unknowns. By chanfing the concentration of this element in two additionally prepared samples further data are obained permitting the derivation of two more equations. Solution of these three equations by algebraic or graphical methods yields the concentration of the elemen. Formulae have been derived desribing ten experimental variants of this principle. Three of these formulae are similar to those described by sherman and Tertian. The other two describe the semi‐emipirical methods of addition, and mixing‐dilution developed by Jones.The experimental data for eleven elements involving ten kα lines, two Kβ lines and one Lα line were obtained using two X‐ray units. The samples were investigated in the form cf liquid, powder pellet, glass disc and powdered glass disc. Only the three most general formulae have used in the calculations. Results show absolute percentage deviations with