SODIUM THIOSULFATE

Sodium Thiosulfate is a commonly used chemical material, as the fixing agent in photography, film and printing plate-making industry, as a reducing agent used in tanning. 
Sodium Thiosulfate is used as a bleaching agent for removing residual and a mordant in the paper and textile industries, as antidotes of cyanide poisoning in medicine, as dechlorination agent and fungicides of drinking water and wastewater in water treatment, as a copper corrosion inhibitor of circulating cooling water and a deoxidizer of boiler water systems. 
Sodium Thiosulfate is also used for Cyanide wastewater treatment. 

CAS:    7772-98-7
MF:    Na2O3S2
MW:    158.11
EINECS:    231-867-5

Synonyms
DECHLORINATING SOLUTION;HYPO;'HYPO';BETZ 0235;ANTICHLOR;SODIUM HYPOSULFITE;SODIUM THIOSULFATE;SODIUM THIOSULFATE, 2.00 N

Soda ash and sulfur are generally used as raw materials in industry, soda ash reacts with sulfur dioxide produced by the combustion of sulfur to produce sodium sulfite, then add sulfur for boiling reactions, and then filter, bleach, concentrate and crystallize, etc, can obtain sodium thiosulfate pentahydrate. 
Other production waste containing sodium sulfide, sodium sulfite, sulfur and sodium hydroxide can also be used, after appropriate treatment to get the product.
An inorganic sodium salt composed of sodium and thiosulfate ions in a 2:1 ratio.
Sodium Thiosulfate can be obtained from Na2S2O3.10H2O by heating above 100 °C. 
Sodium Thiosulfate can be synthesized from sodium sulfate.
Sodium Thiosulfate is an inorganic compound with the formula Na2S2O3·(H2O)x. 
Typically Sodium Thiosulfate is available as the white or colorless pentahydrate (x = 5), which is a white solid that dissolves well in water. 
Sodium Thiosulfate is a reducing agent and a ligand, and these properties underpin its applications.

Sodium Thiosulfate Chemical Properties
Melting point: 48°C
Boiling point: 100°C
Density: 1.01 g/mL at 25 °C
Bulk density: 1350kg/m3
Storage temp.: Store at +5°C to +30°C.
Solubility: Immiscible with alcohol.
Form: Solid
Specific Gravity: 1.667
Color: White
PH: 6.0-8.5 (25℃, 50mg/mL in H2O)
Water Solubility: Soluble in water. Insoluble in alcohol.
Sensitive: Hygroscopic
Merck: 14,8694
Stability: Stable. Incompatible with strong acids, strong oxidizing agents, iodine, mercury.
InChIKey: AKHNMLFCWUSKQB-UHFFFAOYSA-L
LogP: -0.428 (est)
CAS DataBase Reference: 7772-98-7(CAS DataBase Reference)
EPA Substance Registry System: Sodium Thiosulfate (7772-98-7)

Sodium Thiosulfate is colorless monoclinic crystal or white crystalline powder, Odorless, salty ignorant. 
The relative density is 1.667. 
Soluble in water, the solubility is 231 g/100 ml of water at 100 ℃. 
Insoluble in alcohol. 
deliquescence easily in air. 
With a strong reductibility, decomposition in acidic solution.
Sodium Thiosulfate, Na2S203·5H20, also known as sodium hyposulfite, hypo,andsodium subsulfite, is a white crystalline solid that has a melting point of 48 °C(118 °F). 
Water soluble, Sodium Thiosulfate is used as a fixing agent for photographic films, plates, and papers. 
Sodium Thiosulfate is used in medicine, as a germicide, in manufacturing leather, as a mordant in dyeing, and for extracting silver from ore.

Physical properties    
Sodium Thiosulfate has two forms as anhydrous sodium thiosulfate (Na2S2O3) and Sodium Thiosulfate pentahydrate (Na2S2O3 · 5H2O), the latter is also known as soda and Hyperion. 
A molecular weight is 158.11 and 248.18 respectively. 
Anhydrous Sodium Thiosulfate is an opaque crystalline powder. 
The relative density is 1.667. 
Sodium Thiosulfate is odorless, salty taste, soluble in water, insoluble in ethanol. 
Sodium Thiosulfate decomposes in acidic solution, has a strong reduction, easily absorbs moisture. 
Sodium Thiosulfate is odorless, colorless and transparent monoclinic crystals or granules. 
The relative density is 1.685. 
The melting point is 48 ℃. 
Sodium Thiosulfate loses all crystal water at 100 ℃, and decomposes above 100 ℃. 
Sodium Thiosulfate is easily weathered in dry and hot air, slightly deliquescence in the hot and humid air. 
Sodium Thiosulfate is soluble in water and turpentine, insoluble in ethanol, decomposes in case of strong acid. 
Prolonged exposure in the air, Sodium Thiosulfate is easily oxidated and carbonized by oxygen and carbon dioxide.
Sodium Thiosulfate is a white powder; soluble in water; insoluble in ethanol.
Sodium Thiosulfate is a colorless, odorless, crystalline solid; density 1.69 g/cm3; decomposes around 50°C; effloresces in dry air above 33°C; very soluble in water and oil of turpentine; insoluble in ethanol.

Reactions    
With reductibility, Sodium Thiosulfate is a medium strength reducing agent, for example, can be oxidated by chlorine:
Na2S2O3 + 4Cl2 + 5H2O = Na2SO4 + H2SO4 + 8HCl
This reaction is used in textile and paper industries, and Sodium Thiosulfate is used as dechlorination agent. 
Again, Sodium Thiosulfate can be oxidized to sodium tetrathionate by iodine:
Na2S2O3 + I2 = Na2S4O6 + 2Nal
This reaction is used in analytical chemistry for quantitative determination of iodine.
Sodium Thiosulfate is also used in tanning, extracts silver from the ore and so on. 
Since there are different oxidation states of sulfur in sodium thiosulfate molecule, Sodium Thiosulfate is stable in alkaline medium, unstable an acidic medium, oxidation-reduction reaction occurs when acidification, separate out sulfur:
Na2S2O3 + H2SO4 = Na2SO4 + H2S2O3 H2S2O3 = H2SO3 + S H2SO3 = H2O + S02.
With coordination, thiosulfate ions can form stable complexes with certain metal ions, for example, silver bromide can be dissolved in an aqueous solution of hypo to produce stable [Ag (S2O3) 2] 3-complex ions:
AgBr + 2Na2S2O3 = Na3 [Ag (S2O3) 2] + NaBr, so it is commonly used as a photographic fixing bath. 
Sodium Thiosulfate and sulfur are boiled, and then filtration, evaporation, crystallization to prepare sodium thiosulfate.

Uses    
1. Sodium Thiosulfate is Used in manufacture of the fixing powder and preparation of the photographic industry fixer, desiccant. 
Used as a reducing agent of dichromate in leather tanning industry.
2. Sodium Thiosulfate is an important inorganic chemical raw material. 
Sodium Thiosulfate can be used in the synthesis of pesticides Bisultap, Thiosultap disodium, CARTAP and so on.
3. Used as analytical reagents, mordant and fixer.
4. Used as new insecticides, with stomach poisoning, uptake and contact action effects, Sodium Thiosulfate can prevent and treat rice yellow stem borer, stem borer, leaf roller, rice thrips and vegetables, fruit pests.

5. With uptake and strong contact, stomach poisoning effects, Sodium Thiosulfate can prevent and treat various rice pests and vegetables, fruit pests.
6. Used as the chlorine removal agent for Pulp and cotton fabric bleached, as chelating agents, anti-oxidants in the food industry, as detergents, disinfectants in the pharmaceutical industry.
7. Used as chelating agents, antioxidants, anti-browning agent, as the dechlorination agent of chlortetracycline hydrochloride (or chlortetracycline) chilled with ice, dechlorination reaction is as follows:
More chlorine content will cause side reactions of free sulfur, so only used for very dilute concentrations of chlorine.
Used as salt chelating agent, limited content is 0.1% or less.

Sodium Thiosulfate is a common analytical reagent used in iodometric titration to analyze chlorine, bromine, and sulfide. 
Other uses are in bleaching paper pulp, bleaching straw, ivory, and bones, for removing chlorine from solutions, silver extraction from its ores, a mordant in dyeing and printing textiles, and as an antidote to cyanide poisoning.
Another major application is in photography, where Sodium Thiosulfate is used as a fixer to dissolve unchanged silver salts from exposed negatives.
Sodium Thiosulfate is used primarily as a medicament against cyanide poisoning, able to convert cyanide into thiocyanate, a reaction which is catalyzed by the enzyme Rhodanese. Antioxidant.
Sodium Thiosulfate is a sequestrant, antioxidant, and formulation aid that is a powder soluble in water. 
Sodium Thiosulfate can be used in alcoholic bev- erages at 5 ppm and in table salt at 0.1%. Sodium Thiosulfate is also termed sodium hyposulfite.
Sodium thiosulfate (thiosulfate) Known simply as “hypo,” an abbreviated form of the incorrect form hyposulfite, this white crystal was made by boiling calcium thiosulfate with sodium sulfate. 
Sodium Thiosulfate is soluble in water and oil of turpentine but not in alcohol. 
The property of sodium thiosulfate to dissolve silver halides was discovered in 1819 by Sir John Herschel and was probably first used to fix photographic images by L. J. M. Daguerre. After Daguerre published its use in his 1839 manual W. H. F. Talbot finally used it to fix calotype negatives and silver chloride prints, although he continued to stabilize them with potassium iodide and sodium chloride presumably for the variety of colors possible. 
Sodium Thiosulfate was the primary fixing agent throughout the 19th century and is still used today.

Sodium Thiosulfate is used predominantly in dyeing. 
Sodium Thiosulfate converts some dyes to their soluble colorless "leuco" forms. 
Sodium Thiosulfate is also used to bleach "wool, cotton, silk, ...soaps, glues, clay, sand, bauxite, and... edible oils, edible fats, and gelatin."

Medical uses
Sodium Thiosulfate is used in the treatment of cyanide poisoning.
Sodium Thiosulfate is on the World Health Organization's List of Essential Medicines.
Other uses include topical treatment of ringworm and tinea versicolor, and treating some side effects of hemodialysis and chemotherapy.
In September 2022, the U.S. Food and Drug Administration (FDA) approved sodium thiosulfate under the trade name Pedmark to lessen the risk of ototoxicity and hearing loss in infant, child, and adolescent cancer patients receiving the chemotherapy medication cisplatin.

Structure
Two polymorphs are known as pentahydrate. 
The anhydrous salt exists in several polymorphs.
In the solid state, the thiosulfate anion is tetrahedral in shape and is notionally derived by replacing one of the oxygen atoms by a sulfur atom in a sulfate anion. 
The S-S distance indicates a single bond, implying that the terminal sulfur holds a significant negative charge and the S-O interactions have more double-bond character.

Preparation    
Sodium Thiosulfate is an important chemical commodity that is known to photographers as "hypo". 
Sodium Thiosulfate can be prepared by the reaction of Sodium Thiosulfate and the bisulphite with H2S:
2Na2S03 + 2NaHS03 + 2H2S -> 3Na2S203 + 3H20
Sodium Thiosulfate can also be prepared by the reaction of sulphur with sodium sulphite above 60 °C
Na2SO3 + S -> Na2S2O3 and by the reaction of H2S and permanganate.
Sodium Thiosulfate decomposes at 310°C to form sulphur and Na2S03 , and at 400°C to form Na2S4 and Na2S. 
Sodium Thiosulfate absorbs S02 to form free sulphur and Na2S04 . 
Sodium thiosulphate forms many hydrates and their solubility relationships are quite complex.

Sodium Thiosulfate is a common reducing agent. 
Sodium Thiosulfate reduces iodine to iodide anion forming sodium tetrathionate. 
This reaction is utilized in the so-called iodometric titration: 2S2O32ˉ + I2 → S4O62ˉ + 2Iˉ
Sodium Thiosulfate reacts with chlorine to form sodium bisulfate and hydrochloric acid. This reaction removes chlorine from aqueous solutions:Na2S2O3 + 4Cl2 + 5H2O → 2NaHSO4 + 8HCl
Sodium Thiosulfate reacts with hydrochloric acid, decomposing to sulfur and sulfur dioxide: Na2S2O3 + 2HCl → 2NaCl + S + SO2 + H2O.

Production
Sodium Thiosulfate is prepared by oxidation of sodium sulfite with sulfur.
Sodium Thiosulfate is also produced from waste sodium sulfide from the manufacture of sulfur dyes.
This salt can also be prepared by boiling aqueous sodium hydroxide and sulfur according to the following equation.
However, Sodium Thiosulfate is not recommended outside of a laboratory, as exposure to hydrogen sulfide can result if improperly handled.

6 NaOH + 4 S → 2 Na2S + Na2S2O3 + 3 H2O

Production method    
1. Sodium Thiosulfate is generated by heat of a solution of sodium sulfite and sulfur powder.
2. There are more synthesis methods of Sodium Thiosulfate, such as sodium sulfite method, sodium sulfide method and so on.
Sodium sulfite method
Soda solution reacts with sulfur dioxide gas, and caustic soda was added, adding sodium sulfide to remove impurities by filtration, and then sulfur powder was dissolved in a hot solution of sodium sulfite to react, filter, remove impurities, and then filter repeatedly, add caustic alkali to process, through concentration, filtration, crystallization, centrifugal dewatering, screening, to obtain the finished product of sodium thiosulfate. 
Reaction equation: Na2CO3 + SO2 = Na2SO3 + CO2 ↑
Na2SO3 + S + 5H2O = Na2S2O3 · 5H20

Sodium sulfide method
A raw material liquid formulated from sodium sulfide evaporation residue, barium sulfide wastewater (containing sodium carbonate and sodium sulfide) reacts with sulfur dioxide, sulfur powder was added after clarification, heated to react, evaporation, cooling crystallization, washing, separation, screening to obtain sulfur thiosulfate products. Reaction equation: 2Na2S + Na2CO3 + 4SO2 = 3Na2S2O3 + CO2 ↑
2Na2S + 3Na2CO3 + 6SO2 + 2S = 5Na2S2O3 + 3CO2 ↑
3. Dehydration method is that heat sodium thiosulfate pentahydrate crystalline indirect with steam, Sodium Thiosulfate dissolves into itself crystal water, concentration, centrifugal dewatering, drying, screening, to obtain the finished product of anhydrous sodium thiosulfate.
Na2S2O3 · 5H20 → Na2S2O3 + 5H2O