Sodium thiosulfate

Industrial production and laboratory synthesis
On an industrial scale, sodium thiosulfate is produced primarily from waste liquid sodium sulfide or sulfur dye manufacture. In the laboratory, this salt is prepared by heating an aqueous solution of sodium sulfite with sulfur.
Main reactions and applications
Sodium thiosulfate
Thiosulfate anion characteristically reacts with dilute acids to produce sulfur dioxide, sulfur and Water:
2NaCl Na2S2O3 + 2HCl + S + SO2 + H2O
This reaction is known as a clock reaction, because when the sulfur reaches a certain concentration of the solution changes color to a pale yellow. This reaction is used to generate colloidal sulfur. When protonation takes place at low temperatures, H2S2O3 (thiosulphuric acid) can be obtained. This is a strong acid pKa = 0.6, 1.7.
Iodometry
In chemical analysis, the most important use stems from the fact that the anion thiosulfate reacts stoichiometrically with iodine, which reduces to iodide, as it is oxidized to tetrathionate:
2 S2O32 (aq) + I2 (aq) S4O62 (aq) + 2 I (aq)
Due to the quantitative nature of this reaction and the fact that Na2S2O35H2O has an excellent preservation of life, is used as titrant in iodometry. Na2S2O35H2O is also a component of the iodine clock experiment.
This particular application can be configured to measure the oxygen content of the water through a long series of reactions. It is also used in estimating volumetric concentrations of certain compounds in solution (hydrogen peroxide, for example) and to estimate the content of chlorine in bleaching powder and water trading.
photographic processing
The sulfur atom binds terminal S2O32 of soft metals with high affinity. Therefore, silver halide, eg AgBr, typical components of photographic emulsions, dissolved in dealing with aqueous thiosulfate:
2 [Ag (S2O3) 2] S2O32 AgBr + 3 + Br-
In this application, photo processing, discovered by John Herschel and uses both film and paper processing photo, sodium thiosulfate is known as a photographic fixer, and is often referred to as hypo, from the original chemical name, thiosulphate of soda.
Extraction gold
sodium thiosulfate is a component of an alternative lixiviant to cyanide for gold extraction. It forms a strong complex of gold (I) ions, [Au (S2O3) 2] 3 -. The advantage of this approach is that thiosulfate is essentially non-toxic and that the types of minerals that are refractory to cyanidation of gold (eg, carbonaceous-type ores or Carlin) can be carried by the thiosulfate. Some problems with this alternative process include the high consumption of thiosulfate, and the lack of a proper recovery technique as [Au (S2O3) 2] 3 – not adsorb to activated carbon, which is the standard technique used in gold cyanidation to separate the complex mixture of gold ore.
Analytical Chemistry
sodium thiosulfate is also used in analytical chemistry. You can, when heated with a sample containing aluminum cations, produce a white precipitation:
3S2O32 2Al3 + + 3SO2-+ 3H2O + 3S + 2Al (OH) 3
Medical
It is used as an antidote to poisoning cyanide. Thiosulfate acts as a sulfur donor for the conversion of cyanide to thiocyanate (which can be safely excreted in the urine), catalyzed by the enzyme rhodanase.
It has also been used as a treatment of calciphylaxis in hemodialysis patients with end stage renal disease.
in footbaths for the prophylaxis of ringworm, and as a topical antifungal agent of tinea versicolor.
in measuring the volume of extracellular body fluids and renal glomerular filtration rate.
Other uses
sodium thiosulfate is also used:
As a component of hand warmers and other chemical heating pads that produce heat exothermic crystallization of a super solution.
In Bleach
In tests of pH of chlorinated substances. The universal indicator pH and other liquid indicator are destroyed by chlorine, making them useless for pH testing. If you first add sodium thiosulfate to these solutions, they neutralize the effects of color removal from bleach and allows to test the pH of the solutions of chlorine liquid indicators. The corresponding reaction is similar to the reaction of iodine reduce thiosulfate hypochlorite (active ingredient in bleach) and it is oxidized to sulfate. The overall reaction is:
Na2S2O3 4 NaClO + NaCl + 2 4 + 2 NaOH + Na2SO4 H2O
To dechlorinate tap water for aquariums or treat effluent wastewater treatment before release into rivers. The reduction reaction is analogous to the reduction reaction of iodine. The treatment of tap water requires between 0.1 grams and 0.3 grams of pentahydrate (Crystal) sodium thiosulfate for every 10 liters of water.
To lower the chlorine levels in pools and spas following super chlorination.
To remove stains from iodine, for example, after the explosion nitrogen triiodide.
In the bacteriological evaluation.
In tanning leather.
To demonstrate the concept of reaction rate in class chemistry. The thiosulfate ion can decompose in the sulfite ion and a colloidal suspension of sulfur, which is opaque. The equation for this reaction is catalyzed by acids the following:
S2O32 (aq) SO32 (aq) + S (s)
To demonstrate the concept of supercooling in physics classes. molten sodium thiosulfate is very easy cool to room temperature and when the crystallization is forced, the jump in temperature of 48.3C can be experienced by touch.
As part of the patina recipes for copper alloys.
It is often used in pharmaceutical preparations as an anionic surfactant to aid dispersion.
You can also use as a very interesting experiments solute supersaturation.
References
Ab ^ Holleman, AF, Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5
^ Robert Charles Gibson (1908). The romance of modern photography, discovery, and their achievements. Seeley & Co. p. 37. http://books.google.com/books?id=whYaAAAAMAAJ&pg=PA37&dq=hyposulphite-of-soda+herschel+fixer+hypo&lr=&as_brr=1&as_pt=ALLTYPES&ei=czVdSaipAYWekwSc_vW5Dg.
^ Aylmore, MG, Muir, DM "thiosulfate leaching of gold – a review, Minerals Engineering, 2001, 14, 135-174
^ "Toxicology Cyanide: Overview – eMedicine. http://emedicine.medscape.com/article/814287-overview. Retrieved on 2009-01-01.
Hall AH, Dart R, Bogdan G (June 2007). "Sodium thiosulfate or hydroxocobalamin for the empiric treatment of cyanide poisoning?". Ann Emerg Med 49 (6): 80,613. doi: 10.1016/j.annemergmed.2006.09.021. PMID 17098327.
^ Cicone JS, Petronis JB, Embert CD, Spector DA (June 2004). "The successful treatment of calciphylaxis with sodium thiosulfate intravenous "I'm J. Kidney Dis 43 (6 ):… 11,048 doi: .. 10.1053/j.ajkd.2004.03.018 PMID 15168392.
Sodium thiosulfate ^ Dorland's Medical Dictionary
EV
Sodium compounds
NaAlO2 NaBH3 (NC) NaBH4 NaBr NaBrO4 NaCH3COO NaC6H5CO2 NaC6H4 NaCN (OH) CO2 NaClO2 NaClO NaClO 3 NaCl NaHCO3 NaH NaClO4 NaF NaI NaHSO3 NaHSO4 NaIO3 NaIO4 NaNH2 NaMnO 4 Na2O NaOH NaNO3 NaNO2 NaN3 NaPO2H2 NaReO4 NaSCN NaSH NaTcO4 NaVO3 Na2CO3 Na2C2O4 Na2CrO4 Na2Cr2O7 Na2MnO4 Na2MoO4 Na2O Na2O2 Na2O (UO3) 2 Na2S Na2SO3 Na2SO4 Na2S2O3 Na2S2O4 Na2S2O5 Na2S2O6 Na2S2O7 Na2SeO3 Na2S2O8 Na2SeO4 Na2SiO3 Na2Te Na2TeO3 Na2Ti3O7 Na2U2O7 NaWO4 Na2Zn (OH) 4 Na3P Na3N Na4Fe Na3VO4 (CN) 6 Na5P3O10
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