text: For the rest of his life Auer von Welsbach turned again to "pure" chemistry. He worked largely on his estate at Welsbach Castle (Schloß Welsbach) near Treibach near Althofen. In addition to his work on elements and minerals, he made advances in the development of photographic techniques.  He was also a devoted gardener, carefully supporting rare and difficult-to-grow plants in his garden, and breeding new varieties of roses and apple trees.
  He published a number of papers on chemical separation and spectroscopy, working on radioactive elements as early as 1904.  In 1910, one of his companies helped to establish Vienna as a center of radiation research by producing the first major quantity of radium chloride (3-4 grams) in Europe.
  In 1910, Auer von Welsbach reported a "mysterious observation", the induction of radioactivity in an inactive substance when exposed to a radioactive substance. Based on his report, it is possible that he may have been the first to observe neutron activation.
  Between 1907 and 1918, Auer von Welsbach focused on isolating preparations of actinium  and  thorium as by-products of radium extraction.
  He kept up an active correspondence with physicist Stefan Meyer, managing director of the Institute for Radium Research, Vienna, to discuss the extraction of actinium. Meyer and his staff do not appear to have had the chemical knowledge to understand Auer von Welsbach's methods, and Auer von Welsbach resigned around 1917.
  During World War I, he had difficulty finding staff to carry out research.  After the war, he was active in supporting the work of the institute, and other scientists.
  He presented a major paper on his spectroscopic work and the separation of radioactive elements in 1922.
  The following photographs show scientific equipment from Auer von Welsbach's laboratory, from "Spektroskopische Methoden der analytischen Chemie" (1922).