Sodium Thiosulfate Supplier South Africa

What Is Sodium Thiosulfate?

Sodium thiosulfate (Na₂S₂O₃·5H₂O, hypo) is an inorganic sodium compound containing the thiosulfate anion (S₂O₃²⁻). It is a reducing agent and a chlorine scavenger — it rapidly reacts with chlorine and chloramines in aqueous solution to neutralise them, converting them to chloride. This chlorine-neutralising (dechlorination) property makes sodium thiosulfate the standard reagent for quenching residual chlorine in water samples before microbial analysis, for dechlorinating chlorinated wastewater prior to discharge, and for conditioning tap water in aquaculture and aquarium systems by removing chlorine and chloramines harmful to aquatic organisms.

Water Treatment Dechlorination

In municipal wastewater treatment, sodium thiosulfate is used to remove residual chlorine from final effluent before discharge to surface water, protecting aquatic life from chlorine toxicity. In industrial water treatment, it is used to remove residual oxidant after hypochlorite or chlorine biocide treatment prior to discharge. In water microbiology laboratories, thiosulfate-neutralised sample bottles (pre-loaded with sodium thiosulfate) are used for chlorinated water sample collection — thiosulfate immediately neutralises chlorine in the sample, stopping disinfection activity and preventing continued kill of microorganisms in transit, allowing accurate viable bacterial counts. In aquarium and aquaculture water conditioning, thiosulfate removes both chlorine and chloramines (unlike ascorbic acid, which removes only chlorine).

Photographic and Industrial Applications

In photographic processing, sodium thiosulfate (hypo) is the fixing agent for silver halide photographic films and papers — it dissolves unexposed silver halide grains (AgBr, AgCl) by forming soluble silver thiosulfate complexes, clearing the unexposed regions of the photographic emulsion and fixing the developed image. In other industrial applications, it is used as a reducing agent, as an antichlor in textile processing (to remove residual bleach), and in pharmaceutical preparation of sodium nitroprusside solutions. Terracore Chemicals supplies sodium thiosulfate pentahydrate in 25 kg bags for water treatment and industrial applications.