Bisulfide
A bisulfide is a chemical compound containing the HS- anion. The term is somewhat ambiguous, as it can refer to several different classes of chemical compounds depending on context. It can denote:
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An inorganic salt: A salt containing the bisulfide anion (HS-), also known as hydrosulfide. These salts are typically formed by partially neutralizing hydrogen sulfide (H2S) with a base. Examples include sodium bisulfide (NaHS) and potassium bisulfide (KHS). In aqueous solution, the bisulfide ion is in equilibrium with sulfide (S2-) and hydrogen sulfide (H2S), with the equilibrium shifting depending on pH.
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An organic compound: An organic compound containing a thiol group (-SH). In this context, the term is often used informally or historically, as "thiol" is the preferred and more accurate term in modern chemical nomenclature. For example, methyl bisulfide might refer to methanethiol (CH3SH).
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A compound containing an -S-S- bridge: This is a less common usage but could, in principle, be interpreted as implying a disulfide bond bridged by a proton. This interpretation is less standardized.
The term's use is often discouraged in favor of more precise terminology, especially when referring to organic compounds. Always consider the context to determine the intended meaning. When referring to inorganic compounds, specify the cation (e.g., sodium bisulfide) to avoid ambiguity.