What chemical is used to dechlorinate water samples that have been chlorinated?

Sodium thiosulfate is a widely utilized chemical for dechlorination because it effectively reacts with chlorine, neutralizing it and preventing it from interfering with subsequent analyses or processes. When added to chlorinated water, sodium thiosulfate converts chlorine into a less reactive form, enabling accurate testing for various parameters without the influence of residual chlorine. This property makes sodium thiosulfate the preferred choice in environmental health and water quality assessments, particularly when preparing samples for microbiological testing or chemical analysis.

The other chemicals listed do not serve the same specific purpose as sodium thiosulfate in dechlorination. Sodium sulfate, for instance, does not interact with chlorine; instead, it serves different roles, such as being a drying agent in chemical processes. Sodium bisulfate can lower pH but has limited efficacy in dechlorinating water, while sodium bisulfite can also reduce chlorine but is less commonly used in standard dechlorination practices compared to sodium thiosulfate.