that he stay in Leipzig as a private lecturer, but Walden declined, hoping for a better career in Riga. In the summer of 1892 he was appointed assistant professor of physical chemistry. A year later he defended his doctorate on osmotic phenomena in sedimentary layers and in September 1894 became professor of analytical and physical chemistry at the Riga Technical University. He worked there until 1911 and during 1902–1905 was rector of the university. In 1895, Walden made his most remarkable discovery which was later named Walden inversion, namely that various stereoisomers can be obtained from the same compound via certain exchange reactions involving hydrogen. This topic became the basis for his habilitation thesis defended in March 1899 at St. Petersburg University. After that, Walden became interested in electrochemistry of nonaqueous solutions. In 1902, he proposed a theory of autodissociation of inorganic and organic solvents. In 1905, he found a relationship between the maximum molecular conductivity and viscosity of the medium and in 1906, coined the term "solvation". Together with his work on stereochemistry, these results brought him to prominence; in particular, he was considered a candidate for the Nobel Prize in Chemistry in 1913 and 1914. Walden was also credited as a talented chemistry lecturer. In his memoirs, he wrote: "My audience usually was crowded and the feedback of sympathetic listeners gave me strength ... my lectures I was giving spontaneously, to bring freshness to the subject ... I never considered teaching as a burden". 1896 brought reforms to the Riga Technical University. Whereas previously, all teaching was conducted in German and Walden was the only professor giving some courses in Russian, from then on, Russian became the official language. This change allowed receiving subsidies from the Russian government and helped the alumni in obtaining positions in Russia. These reforms resulted in another and rather unusual collaboration of Walden with Ostwald: Walden was rebuilding the Chemistry Department and Ostwald sent him the blueprints of the chemical laboratories in Leipzig as an example. In May 1910, Walden was elected a member of the St. Petersburg Academy of Sciences and in 1911 was invited to Saint Petersburg to lead the Chemical Laboratories of the academy founded in 1748, by Mikhail Lomonosov. He remained in that position till 1919. As an exception, he was allowed to stay in Riga where he had better research possibilities, but he was traveling, almost every week,