A New Alumina Trihydrate

DURING the development of a platinum-alumina catalyst, X-ray studies have revealed that, in addition to the well-known gibbsite and bayerite, a third crystalline form of Al(OH) 3 exists. Pure samples of this new trihydrate have not been obtained. It is generally accompanied by bayerite, often by both bayerite and gibbsite. In samples where this new crystalline trihydrate is the major component, it has been possible to determine its chemical composition as Al(OH) 3 and to resolve its X-ray diffraction pattern. This pattern of the new phase (as recorded with a Geiger counter spectrometer using copper K α radiation) is: