Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
sulfuric, sulfureous, sulfurous, sulfury (adjs.)
All four are adjectives made by adding adjectival endings to the noun sulfur (also spelled sulphur). All mean “of, relating to, containing, or somehow like sulfur,” but sulfuric and sulfurous have explicit technical senses as well: sulfuric, as in sulfuric acid (H2SO4), refers specifically to a hexavalent sulfur, that is, an atom of sulfur capable of bonding with six atoms or molecular groups. Technically, sulfurous is used by the chemist only of tetravalent or bivalent sulfur, but its figurative meanings are broad and colorful, particularly in the “hellfire” cluster of senses. Sulfury and sulfureous both are very general: “sulfurlike” or “containing sulfur.” All these uses (and more) are Standard.
