Bisulfidem

Bisulfidem is a term that does not have a single, universally accepted definition in modern chemistry. In practice, it has appeared in older literature and in non-English sources with varying meanings, typically relating to sulfur-sulfur chemistry or to sulfide ligands. Because of the lack of standardization, the precise interpretation of bisulfidem must be inferred from context.

One possible meaning is a reference to the disulfide dianion S2^2−, known in common salts as disulfide or sodium rhodium? No, sodium disulfide Na2S2, potassium disulfide K2S2, and related salts contain the S2^2− unit. In this sense, bisulfidem would be an older or alternate name for the disulfide dianion rather than a neutral molecule. These salts are typically basic and can be oxidized or hydrolyzed to other sulfur species under appropriate conditions.

A second, less standardized interpretation occurs in some linguistic traditions where bisulfidem is used to describe a neutral disulfide compound of the form R–S–S–R (a typical organic disulfide) or a general two-sulfide linkage within a molecule. In modern IUPAC nomenclature, however, the term disulfide is preferred for such S–S bonded species, and bisulfide tends to be avoided to prevent ambiguity.

Overall, bisulfidem is best avoided in contemporary texts in favor of more precise terms such as disulfide, disulfide dianion, or hydrosulfide/ sulfide, depending on the chemical species being described. When encountered, the term should be clarified by explicit formula or description to prevent misinterpretation. See also disulfide, sulfide, and hydrosulfide.