thiosulfate

This term is used exclusively within the domains of inorganic chemistry and biochemistry. It describes a specific chemical species characterized by the presence of two sulfur atoms, one of which is centrally bonded to three oxygen atoms. In laboratory settings, it is most frequently encountered as sodium thiosulfate, a compound used extensively in iodometric titrations and as a photographic fixer.

As a technical chemical term, it functions as a mass noun when referring to the substance in general or as a countable noun when referring to specific types of thiosulfate salts. It carries a neutral, scientific register and is never used in casual or metaphorical conversation.