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Learn about Sodium Thiosulphate, its general methods of preparation, assay techniques, properties, and medicinal applications. Explore its importance in medicine and industry.
Introduction
Sodium thiosulphate (Na₂S₂O₃) is a widely used inorganic compound known for its crucial role in poison treatment and industrial applications. It acts as an emergency antidote for poisoning, particularly in cases of cyanide toxicity, by neutralizing toxins and facilitating their safe removal from the body. Apart from its medical significance, sodium thiosulphate is used in water purification, photography, and analytical chemistry. This article explores its preparation methods, assay techniques, medicinal uses, and chemical properties, highlighting its importance in both the healthcare and industrial sectors.
General Methods of Preparation
Sodium thiosulphate can be prepared using various chemical methods. Some of the commonly used methods include:
1. Reaction of Sodium Sulfite with Sulfur
This method involves the dissolution of sulfur in a sodium sulfite (Na₂SO₃) solution.
2. Reaction of Sodium Hydroxide with Sulfur Dioxide and Sulfur
In this method, sulfur dioxide gas is passed through a sodium hydroxide solution in the presence of elemental sulfur to form sodium thiosulphate.
3. Byproducts of Photography and Industrial Processes
Sodium thiosulphate is sometimes obtained as a byproduct in industries dealing with sodium sulfate or during the fixation process in photography where silver thiosulphate complexes are formed.
Assay of Sodium Thiosulphate
Sodium thiosulphate is assayed using iodometry, a redox titration technique. The principle is based on the reaction of sodium thiosulphate with iodine:
The endpoint of the titration is detected using starch as an indicator, which forms a blue complex with iodine that disappears once thiosulphate has completely reacted.
Properties of Sodium Thiosulphate
Physical Properties
Molecular Formula: Na₂S₂O₃·5H₂O (pentahydrate form is most common)
Molecular Weight: 248.18 g/mol (pentahydrate)
Appearance: White crystalline powder
Solubility: Highly soluble in water, slightly soluble in alcohol
Odor: Odorless
Chemical Properties
Reduces halogens like iodine to iodide.
Decomposes on heating to form sodium sulfate, sodium sulfite, and sulfur dioxide.
Forms complexes with metals such as silver, making it useful in photographic development.
Medicinal Uses of Sodium Thiosulphate
Sodium thiosulphate has various therapeutic applications, primarily as an antidote and detoxifying agent. Some of its key medical uses include:
1. Cyanide Poisoning Treatment
Sodium thiosulphate is used in combination with sodium nitrite to treat cyanide poisoning. It works by converting cyanide into a non-toxic thiocyanate, which is then excreted in urine.
2. Antifungal and Antimicrobial Agent
It is used as a topical antifungal in treating tinea versicolor, a skin condition caused by fungal infections.
3. Treatment of Calciphylaxis
Calciphylaxis is a rare and life-threatening condition involving calcium deposition in small blood vessels. Sodium thiosulphate helps by acting as a calcium chelator and promoting the solubility of calcium deposits.
4. Radiation Protection
Studies suggest that sodium thiosulphate may reduce the toxic effects of radiation therapy by scavenging free radicals.
5. Arsenic and Heavy Metal Poisoning
It has chelating properties and is used to detoxify heavy metals such as arsenic and lead.
Industrial and Analytical Applications
Apart from medicinal uses, sodium thiosulphate finds applications in:
- 1. Water purification: As a dechlorinating agent.
- 2. Photographic processing: As a fixing agent to remove unreacted silver halides.
- 3. Textile industry: Used in bleaching and dyeing.
- 4. Analytical chemistry: Utilized in redox titrations and iodometric analyses.
Conclusion
Sodium thiosulphate is a valuable compound with diverse applications in medicine, industry, and analytical chemistry. Its role in poisoning treatment, radiation protection, and antimicrobial therapies highlights its pharmaceutical importance. Understanding its preparation, assay methods, properties, and medicinal uses is essential for healthcare professionals and researchers alike.
Frequently Asked Questions (FAQs)
1. What is sodium thiosulphate used for in medicine?
Answer: Sodium thiosulphate is used as an antidote for cyanide poisoning, a treatment for calciphylaxis, and an antifungal agent for skin infections like tinea versicolor.
2. How does sodium thiosulphate work as an antidote?
Answer: It converts cyanide into a less toxic thiocyanate compound, which is then excreted from the body through urine.
3. Is sodium thiosulphate safe to use?
Answer: Yes, when used as prescribed, sodium thiosulphate is generally safe. However, excessive use may lead to side effects such as nausea, vomiting, and hypotension.
4. Can sodium thiosulphate be used for water treatment?
Answer: Yes, it is commonly used as a dechlorinating agent in water treatment to neutralize excess chlorine in tap water and swimming pools.
5. How is sodium thiosulphate stored?
Answer: Sodium thiosulphate should be stored in a cool, dry place away from direct sunlight and moisture to prevent decomposition.
