Felix Hoffmann in 1890 with the pharmaceutical state exam. In 1891 he graduated magna cum laude from the University of Munich. Two years later he earned his doctorate, also magna cum laude, after completing his thesis entitled "On certain derivatives of dihydroanthracene". In 1894, he joined Bayer as a research chemist. On 10 August 1897 Hoffmann synthesized acetylsalicylic acid (ASA) while working at Bayer under Arthur Eichengrün. By combining salicylic acid with acetic acid, he succeeded in creating ASA in a chemically pure and stable form. The pharmacologist responsible for verifying these results was skeptical at first, yet once several large-scale studies
Phenylarsonic acid was first prepared by Michaelis and Loenser. X-ray crystallography indicates that the molecules are connected by hydrogen-bonds consistent with short distance of 2.5 Å separating the oxygen atoms. The arsenic center is tetrahedral. Several derivatives of phenylarsonic acid have been used as additives for animal feeds. These include 4-hydroxy-3-nitrobenzenearsonic acid (3-NHPAA, or Roxarsone), "p"-arsanilic acid ("p"-ASA), 4-nitrophenylarsonic acid (4-NPAA), and "p"-ureidophenylarsonic acid ("p"-UPAA). Phenylarsonic acid Phenylarsonic acid is the chemical compound with the formula CHAsO(OH), commonly abbreviated PhAsOH. This colourless solid is an organic derivative of arsenic acid, AsO(OH), where one OH group has been replaced by a phenyl group.