sentences:  It was in Berlin that he first became acquainted with Walter H. Schottky who asked him to co-author a book on thermodynamic problems.Together with H Ulich they published ""Thermodynamik"" in 1929, which is still considered a standard reference in the field.In 1930 he was Privatdozent at the University of Jena and published a notable paper with Schottky “"Theorie der geordneten Mischphasen"” (Theory of arranged mixed phases).