X-ray and electron microscope studies on aluminium oxide trihydrates

Summary

Gels and sols of aluminum oxide trihydrate were prepared by five different methods and studied by x-ray diffraction and electron microscopy. The x-ray diffraction analysis has shown that all methods produce mixtures of Gibbsite and Bayerite, the relative proportions of each varying from method to method. A sol and gel prepared by the same method present identical x-ray diffraction patterns and their morphologies are similar in the electron microscope. Two main particle shapes were observed: hexagonal prisms and triangular somatoids. There is experimental evidence which indicates that the former are Gibbsite and the latter, Bayerite. On this basis Willstaetter's methods seem to produce more Bayerite than Gibbsite. The reverse was true for Kraut's method, while in Fricke and Jockers' method, almost pure Bayerite was produced. A platelet structure is proposed for the triangular somatoids.