X-Ray diffraction in the quantitative analysis of crystalline solid phases is used. The evolution of γ-titanium phosphate in the H + Ca 2+ ion exchange is reported. The crystalline phase: TiH 1.25Ca 0.37(PO 4) 2 · 3.5H 2O, which splitts in the Ti(HPO 4) 2 and TiHCa 0.5(PO 4) 2 phases at temperatures higher than 220°C, is characterized. This splitting is the support to propose a method, only using diffractometric data, in order to obtain the relationship of proportionality between the concentration of the crystalline phases in the mixture and the relative intensity of the diffraction lines originated. The analysis method described in this paper can be used for the study of lamellar materials with similar behavior to the one of the γ-titanium phosphate.