1. Rhône-Poulenc Rorer, Department of Pharmaceutical Sciences, Preformulation/Physical Analysis, Research Center of Vitry-Alfortville, 13 quai Jules Guesde, B.P. 14, 94403 Vitry sur Seine Cedex, France, and Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany