hyposulphite

hyposulphite

A chemist carefully weighs a sample of hyposulphite in the laboratory.

Definition
  1. Noun (Chemistry):
    • A salt of hyposulphurous acid: "hyposulphite" refers to a salt containing the anion S₂O₃²⁻. Historically, this term was used for thiosulphate, but in modern chemistry it specifically denotes the dithionite ion (S₂O₄²⁻) or its salts, such as sodium hyposulphite (Na₂S₂O₄), used as a reducing agent.
    • Alternative term for thiosulphate: In older or less formal usage, "hyposulphite" was sometimes applied to thiosulphates (S₂O₃²⁻), though this is now considered obsolete.
Usage Examples

  • In chemistry:

    • Sodium hyposulphite is commonly used in photography as a fixing agent. (A salt of hyposulphurous acid that removes unexposed silver halide.)
    • The laboratory prepared a solution of hyposulphite for the reduction reaction. (A chemical used to reduce other substances.)

  • Historical context:

    • In 19th-century texts, hyposulphite referred to what we now call thiosulphate. (An older term for a different chemical compound.)
Advanced Usage

  • "Hyposulphite of soda": an older name for sodium thiosulphate (Na₂S₂O₃), used in photography and bleaching.

    • The hyposulphite of soda was essential for fixing photographic prints. (A historical chemical application.)

  • "Sodium hyposulphite": modern term for sodium dithionite (Na₂S₂O₄), a strong reducing agent.

    • Sodium hyposulphite is employed in textile dyeing to reduce vat dyes. (A specific industrial use.)
Variants and Related Words

  • Hyposulphurous (adj): relating to hyposulphurous acid (H₂S₂O₄), from which hyposulphites are derived.

    • Hyposulphurous acid is unstable and exists only in solution. (The parent acid of hyposulphite.)

  • Dithionite (n): the modern systematic name for the anion S₂O₄²⁻, synonymous with hyposulphite in current chemistry.

    • Dithionite is preferred over hyposulphite in scientific literature. (A more precise term.)
Synonyms

  • Dithionite: the IUPAC-approved name for the salt of hyposulphurous acid.

    • Sodium dithionite is a synonym for sodium hyposulphite. (Equivalent chemical term.)

  • Thiosulphate (historical): an older synonym for hyposulphite in non-standard usage.

    • In vintage photography manuals, thiosulphate was called hyposulphite. (An overlapping but distinct compound.)
Phrasal Verbs
  • None applicable: "hyposulphite" is a noun and does not form phrasal verbs.
Related Idioms
  • None applicable: "hyposulphite" is a technical term without idiomatic usage.