In the framework of natural phosphate of Hahotoé-Kpogamé (Togo) valorization, a conductimetric study of kinetics of the attack by organics and mineral acids is undertaken at different pH. The mechanisms of complexation of calcium by two humic acids, one extracted in a soil (AHSB) and second in compost (AHC) was carried out. Monitoring of rock dissolution has realised by P2O5 measurement in filtrates, using colorimetric method. The complexation of two humic acids of different origins with the ions Ca2+ by conductimetric and potentiometric methods were carried out. According to the results obtained, importance of rock dissolution depends to solution's acidity whatever the acid origin (organic or mineral). Nonetheless, for humics acids solutions, phosphate dissolution continues in slightly acidic and alkaline solutions. The method of neutralization of the acids humic by the soda based on the derivative of the curve potentiometric made it possible to characterize and to compare the forces of the various acid functions organic materials of different origins has to complex the metal cation.