Educated at Pforta, Orthmann studied at the Martin-Luther-Universität Halle-Wittenberg and the Friedrich-Wilhelms-Universität (today, the Humboldt-Universität zu Berlin).
[1] After receipt of his doctorate, he was a teaching assistant to Peter Pringsheim and Walther Nernst at the University of Berlin.
[1] Orthmann, an assistant to Walther Nernst, helped Lise Meitner build an improved calorimeter with which to measure the average energy per beta particle emitted by Radium E, i.e., 210Bi83.
It was not until the end of 1938, on the initiation of a petition by Herbert Arthur Stuart and Wilhelm Orthmann, who were engaged in physics studies (academic) reform, that the DPG asked Jewish members to withdraw their membership.
[1][5][6][7][8] During World War II, Orthmann was also employed at the Reichsluftfahrtministerium (RLM), finally as a scientific advisor in the development of anti-aircraft artillery.