AbstractBy the application of several modern techniques, a fairly thorough characterization of even the finest oxide powders with respect to particle and crystallite size and shape may be obtained. The application of these techniques is discussed with particular reference to the characterization of a sample of Mg(OH2) and the oxides prepared from it by calcinationin vacuo. The techniques described are, however, exacting and time consuming and whilst invaluable for any basic study cannot, in general, be considered practicable in routine work. For this reason a final section is devoted to a discussion of attempts to“calibrate”the results from conventional techniques in terms of the more fundamental parameters of powder characterization.