* 1867, Dansenberg (Pfalz)
† 1957, Rheinfelden (Baden)
Johannes Pfleger first attended a middle school and then the “Industrial School” in Munich, receiving a diploma in 1884. After completing his military service and a short stay in an infirmary following an accident, he enrolled as a student in the Chemical-Technical Faculty at the Royal Technical University in Munich. Upon completion of his studies in 1891 (when a doctorate at a technical university was not yet possible), he joined Deutsche Gold- und Silber-Scheideanstalt (Degussa AG since 1980 and predecessor of the Chemicals Business Area of Evonik), in Frankfurt am Main as an industrial chemist. Just a year later, as senior electronics chemist, he took over the experimental facility for electrochemistry and electrometallurgy, which was founded jointly by Degussa and Metallgesellschaft AG.
In 1900 Pfleger was appointed research chemist and head of the Degussa experimental department. This promotion heralded both the birth of research in chemistry and of chemical process technology for the company. Johannes Pfleger played a decisive role in the development of a strong chemical branch, in addition to the precious metals processing business. In recognition of his efforts, he was appointed Head Chemist in charge of all the laboratories and process engineering. On April 1, 1933, he retired, but continued to work for Degussa on a freelance basis until 1942.
In the first few years of his employment with Degussa, Pfleger worked chiefly on the cyan chemistry. He discovered how to optimize the Castner process, which had been introduced in 1899 for the manufacture of sodium cyanide. This improved version was used until 1971. Detailed knowledge of the cyanide process was also the trigger for another development, for which he became widely known among experts. Using sodium amide - an intermediate product from the Castner synthesis of sodium cyanide - as a condensation agent in the manufacture of synthetic indigo from phenylglycine in alkali fusion, Pfleger made the manufacture of the highly sought-after blue dye economically, on a large scale. The yields from the Heumann method of indigo synthesis that had been used since 1890 were too low.
The “Pfleger indigo process” patented in 1901 was exploited jointly by the Farbwerke Meister, Lucius & Brüning, the company which later became Hoechst AG, and by Degussa until 1940. For both companies, the Pfleger patent proved extremely profitable: the dye works received a very worthwhile large-scale production facility and, with the large income from the license, Degussa was able to pay dividends of 30, 40 and 50 percent between 1906 and 1911 - rates which meet today with astonishment.
Johannes Pfleger also carried out basic research into active oxygen compounds and chemical bleaches. The new, by today’s standards rather modest, “Bleach and application technology laboratory,” was set up on his initiative. This was the first of its kind in the world and also the birthplace of application technology at Degussa, where processes for bleaching with inorganic peroxides and later with hydrogen peroxide were realized. These results were the foundation for the development of the chemistry behind detergent based materials, such as perborate and percarbonate which are important products of Evonik Industries to this day.
Besides his considerable industrial achievements in the company, there was no lack of honors for Pfleger. In 1911, the Royal Technical University in Munich awarded the “successful researcher in the area of practical electrochemistry” an honorary doctorate in technical science (Dr.-Ing. e. h.). He received a second doctorate from the University of Frankfurt in 1923 in recognition of his technical contribution to the whole field of chemistry and of his pioneering research into the preparation of indigo. Finally, in 1931, the Agricultural University in Berlin named him an honorary citizen for his services in the area of pest control.
* 1867, Dansenberg (Pfalz)