Carl Neuberg's hydrotropic appearances (1916).

Abstract In his 1916 land-mark paper “Hydrotropic appearances”, Carl Neuberg coined the term “hydrotropy”, referring to the solubilisation effect of hydrophobic molecules by small, amphiphilic compounds. In this voluminous work he examines 43 different compounds for their hydrotropic effect and touches on many aspects that later became relevant to hydrotrope science (e.g. applications in pharma, green chemistry, pre-ouzo effect, etc.). Given the significance of his work, it is still widely cited today. However, poor availability and a potential language barrier will severely limit the accessibility for international researchers. Therefore, this translation into the English language seeks to provide access to both, his original thoughts as well as his prolific experimental work on this topic.