1700

Hydrogen Sulfide

Bernardino Ramazzini (1633–1714), Carl Wilhelm Scheele (1742–1786)

Most people have caught a whiff of the “rotten egg” smell of hydrogen sulfide (H₂S), but no living person has ever breathed in a high concentration of it. The human nose can detect the disgusting odor at extremely low concentrations, and that’s a very good thing, since it’s actually more poisonous than hydrogen cyanide (whose smell is, unfortunately, rather faint). As with many other poisonous gases, it kills by damaging the lining of the lungs.

The first person to realize that H₂S was a separate gaseous substance was Italian physician Bernardino Ramazzini. His De morbis artificum diatriba (Diseases of Workers), first published in 1700, was a landmark book in the history of medicine, but it contributed to chemistry as well. Ramazzini noticed that people cleaning out cesspits often had irritated eyes and lungs and that copper or silver coins in their pockets turned black. He hypothesized that all these effects were caused by some irritating gas, formed in the decaying organic matter and released into the air by the workers. The same gas was found around some hot springs and volcanic areas, and its effects on silver and other metals had been noticed in those regions. In 1777, Swedish chemist Carl Wilhelm Scheele produced pure hydrogen sulfide chemically by treating iron pyrite (fool’s gold) with sulfuric acid. He called it Schwefelluft (sulfur air) and described it as “stinking,” as well he might.

Hydrogen sulfide is worth thinking about as a structural analog of water. Sulfur is the next heavier element down the periodic table from oxygen, but H₂S boils away at −76ºF (−60ºC)—nearly 300ºF (150ºC) below the boiling point of H₂O. This is a powerful illustration of hydrogen bonding in that water can form far stronger hydrogen bonds (O to H) than hydrogen sulfide (S to H), which makes water much stickier, stranger, and higher-boiling than any other substance made out of such small molecules.

Iceland’s Holuhraun lava field erupts in 2014 in this false-color infrared image. The plume of gas is a foul and poisonous mixture containing carbon dioxide, sulfur dioxide, and hydrogen sulfide.