Differential thermal analysis (DTA) of Venezuelan laterites.

DTA curves of samples from a residual profile of laterite show two strong endothermic peaks at approx 300o and 525oC and an exothermic peak at approx 985oC. Gibbsite as well as goethite contributed to the endothermic peak around 300oC. The 985o and the 525oC peaks are attributed to kaolinite. The exact location of the exothermic peak is influenced by the presence of goethite, while its shape is influenced by both goethite and gibbsite content. At high gibbsite/kaolinite ratios the endothermic peak of kaolinite is determined by the presence of goethite, but at low ratios this peak is determined by the amount of non-extractable Fe. The position of the endothermic peak of gibbsite is also susceptible to gibbsite/kaolinite ratio. After exhaustive removal of free iron oxides, DTA curves of laterite samples allow differentiation of gibbsite from lateritic goethite. -P.Br.