Sodium Thiosulfate LR Grade POWDER

Sodium Thiosulfate pure LAB GRADE materials

Molecular Formula  ::: Na2S2O3 - 5H2O

 

laboratory synthesis

In the laboratory, this salt can be prepared by heating an aqueous solution of sodium sulphite with sulphur.

Principal reactions and applications

Thiosulfate anion characteristically reacts with dilute acids to produce sulfur, sulfur dioxide and water-

1.Na2S2O3 + 2HCl →2NaCl + S + SO2 + H2O

This reaction is known as a "clock reaction", because when the sulfur reaches a certain concentration the solution turns from colourless to a pale yellow. This reaction has been employed to generate colloidal sulfur. When the protonation is conducted at low temperatures, H2S2O3 (thiosulfuric acid) can be obtained. It is a somewhat strong acid with pKas of 0.6 and 1.7 for the first and second dissociation respectively.

Iodometry

In analytical chemistry, the most important use comes from the fact that the thiosulfate anion reacts stoichiometrically with iodine, reducing it to iodide as it is oxidized to tetrathionate:

Photographic processing

The terminal sulfur atom in S2O32− binds to soft metals with high affinity. Thus, silver halides, e.g. AgBr, typical components of photographic emulsions, dissolve upon treatment with aqueous thiosulfate:

2 S2O32− + AgBr →[Ag(S2O3)2]3−+ Br−

In this application to photographic processing, discovered by John Herschel and used for both film and photographic paper processing, the sodium thiosulfate is known as a photographic fixer, and is often referred to as hypo, from the original chemical name, hyposulphite of soda.

Gold extraction

Sodium thiosulfate is one component of an alternative lixiviant to cyanide for extraction of gold.[3] It forms a strong complex with gold(I) ions, [Au(S2O3)2]3−. The advantage of this approach is th

2 S2O32−(aq) + I2(aq) →S4O62−(aq) + 2 I−(aq)

Due to the quantitative nature of this reaction, as well as the fact that Na2S2O3•5H2O has an excellent shelf-life, it is used as a titrant in iodometry. Na2S2O3•5H2O is also a component of iodine clock experiments.

This particular use can be set up to measure the oxygen content of water through a long series of reactions. It is also used in estimating volumetrically the concentrations of certain compounds in solution (hydrogen peroxide, for instance) and in estimating the chlorine content in commercial bleaching powder and water.at thiosulfate is essentially non-toxic and that ore types that are refractory to gold cyanidation (e.g. carbonaceous or Carlin type ores) can be leached by thiosulfate. Some problems with this alternative process include the high consumption of thiosulfate, and the lack of a suitable recovery technique, since [Au(S2O3)2]3− does not adsorb to activated carbon, which is the standard technique used in gold cyanidation to separate the gold complex from the ore slurry.

Dosage

Process for DE CHLORINATION ::: 

Dissolve the 500 grams of Sodium Thiosulfate in a large pitcher of lukewarm tap water. Stir until all the crystals are dissolved. Then transfer the solution with a funnel to the gallon jug. Top off the jug to make a full gallon of stock solution.

• Add two drops of the stock solution per one gallon of the water to be treated.
• One gallon can treat 37,850 gallons or more. Over-dosage is virtually impossible.

Remarks

Sodium Thiosulfate solutions are almost exclusively used to standardize Iodine solutions or as back-titrants in titrations using Iodine. Solutions of Sodium Thiosulfate are most commonly standardized with Potassium Dichromate or Potassium Iodate solutions, which generate Iodine from Iodide. Starch indicator is typically used. The reaction with Iodine is:

I3- + 2 S2O32- → 3 I- + S4O62- (Dithionite ion)

Titrations with standard Sodium Thiosulfate solution are best conducted in the pH 5 - 9 range. Since this is not always possible, the titrations should be conducted rapidly and with adequate stirring to insure rapid reaction of the Thiosulfate, thus minimizing any acid-accelerated decomposition. This will also minimize the acid-catalyzed oxidation of Iodide (usually present in a titration involving Thiosulfate) to Iodate, which could lead to decreased accuracy.

Sodium Thiosulfate solutions are subject to bacterial decomposition and chemical deterioration. Sodium Thiosulfate solutions decompose in acid solution resulting in the evolution of Sulfur Dioxide gas and precipitation of elemental Sulfur. Contact with Carbon Dioxide in the air can produce the acidity leading to this decomposition, which is faster in more dilute Thiosulfate solutions. 

Supply Locations

Sodium Thiosulfate manufacturer and supplier in Mumbai, Kandla, Kolkata, Chennai, Visakhapatnam, Fujairah, Dubai, Ajman, Abudhabi, Sharjah, Muscat, Oman.