A laboratory scale acid process for the leaching of calcium and iron oxid from a bauxite deposit by hydrochloric acid have been studies at diluted solid liquid phase concentration in a magnetically stirred reactor. The different parameters such as acid strength, temperature, time, solid liquid ratio etc. on two different particles size have been studied. The results have been applied to a model {1-(1-α)1/3}2 = kt. The activation energy found for size fraction below 1.0mm size is 84.3 KJ/mole