Chemistry labs just don’t smell like they used to. When I were a lad, chemistry lessons involved a procedure called Qualitative Inorganic Analysis. This involved bubbling hydrogen sulfide H2S, produced in a Kipp’s apparatus, through solutions to precipitate various metals group by group.
Anyone with a nose knows the rotten-egg odor of hydrogen sulfide - the polite term is gas when it is generated by bacteria living in the human colon. An international team of scientists has discovered that cells inside the blood vessels of mice naturally make the gassy stuff, and that it controls blood pressure.