---
title: Sodium Thiosulfate 5H₂O
date: 2025-03-05T12:12:30Z
modified: 2026-09-16T12:02:30Z
permalink: "https://allanchem.com/sodium-thiosulfate-5h2o/"
type: page
status: publish
excerpt: ""
wpid: 4520
timestamp: 2026-09-16T12:02:30Z
tags: []
---

##### CAS Number

10102-17-7















##### Grade

ACS, USP















##### Packaging

Bag







































Sodium Thiosulfate Pentahydrate, also known as hypo. It is readily soluble in water and possesses unique properties.
**Chemical Formula:** Na2S2O3·5H₂O
**Appearance**: Colorless to white, odorless crystals or powder
**Uses:**
**Medical Applications:** Used as an antidote for cyanide poisoning. It reacts with cyanide to form thiocyanate, which is less toxic and can be excreted by the body. Sodium Thiosulfate is also used in dermatology for the treatment of some skin conditions such as calciphylaxis and calcinosis cutis. It is used in topical formulations to treat some fungal skin infections.
**Food Industry:** It is sometimes utilized as a food additive with specific functions.
**Photography:** Used in photographic processing as a fixing agent. In film and paper photography, it is used to remove unexposed silver halide crystals from the photographic emulsion after development.
**Analytical Chemistry and Laboratory Research:** Used as a titrant in iodometric methods to determine the concentration of oxidizing agents such as chlorine, bromine, and iodine. It is also used as a reducing agent in chemical reactions and as a standard in volumetric analysis.
**Gold Extraction:** Sodium Thiosulfate Pentahydrate is used in the gold mining industry for gold extraction. It is employed as a leaching agent to dissolve gold from ores and concentrates in a process known as the “thiosulfate leach.”
**Additional Applications:** Water treatment to remove residual chlorine from treated water. Textile dyeing processes.







































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