in 1833 bunsen became a lecturer at göttingen and began experimental studies of the (in)solubility of metal salts of arsenous acid. his discovery of the use of iron oxide hydrate as a precipitating agent is still today the most effective antidote against arsenic poisoning. this interdisciplinary research was carried on and published in conjunction with the physician arnold adolph berthold. in 1836, bunsen succeeded friedrich wöhler at the polytechnic school of kassel (). bunsen taught there for three years, and then accepted an associate professorship at the university of marburg, where he continued his studies on cacodyl derivatives. he was promoted to full professorship in 1841. while at university of marburg, bunsen participated in the 1846 expedition for the investigation of iceland's volcanoes.