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. Iodometry
In analytical chemistry, the most important use comes because the thiosulfate anion reacts stoichiometrically with iodine in aqueous solution, reducing it to iodide as the thiosulfate is oxidized to tetrathionate:

2 S2O2−3 + I2 → S4O2−6 + 2 I−Due to the quantitative nature of this reaction, as well as because 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 in the Winkler test for dissolved oxygen. 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. Aluminium cation reaction
Sodium thiosulfate is used in analytical chemistry. It can, when heated with a sample containing aluminium cations, produce a white precipitate:

2 Al3+ + 3 S2O2−3 + 3 H2O → 3 SO2 + 3 S + 2 Al(OH)3

Organic chemistry
Alkylation of sodium thiosulfate gives S-alkylthiosulfates, which are called Bunte salts. The alkylthiosulfates are susceptible to hydrolysis, affording the thiol.
Production
On an industrial scale, sodium thiosulfate is produced chiefly from liquid waste products of sodium sulfide or sulfur dye manufacture.In the laboratory, this salt can be prepared by heating an aqueous solution of sodium sulfite with sulfur or by boiling aqueous sodium hydroxide and sulfur according to this equation:
6 NaOH + 4 S → 2 Na2S + Na2S2O3 + 3 H2O

Principal reactions
Upon heating to 300 °C, it decomposes to sodium sulfate and sodium polysulfide:

4 Na2S2O3 → 3 Na2SO4 + Na2S5Thiosulfate salts characteristically decompose upon treatment with acids. Initial protonation occurs at sulfur. When the protonation is conducted in diethyl ether at −78 °C, 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 dissociations, respectively. Under normal conditions, acidification of solutions of this salt excess with even dilute acids results in complete decomposition to sulfur, sulfur dioxide, and water:
Na2S2O3 + 2 HCl → 2 NaCl + 1/8 S8 + SO2 + H2O

Coordination chemistry
Thiosulfate is a potent ligand for soft metal ions. A typical complex is [Pd(S2O3)2(ethylenediamine)]2-, which features a pair of S-bonded thiosulfate ligands. Sodium thiosulfate and ammonium thiosulfate have been proposed as alternative lixiviants to cyanide for extraction of gold. The advantages of this approach are that (i) thiosulfate is far less toxic than cyanide and (ii) that ore types that are refractory to gold cyanidation (e.g. carbonaceous or Carlin-type ores) can be leached by thiosulfate.