Ammonium thiosulfate

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Ammonium thiosulfate
IUPAC name
Diammonium thiosulfate
Other names
Ammonium thiosulphate
Thiosulfuric acid, ammonium salt (1:2)
Thiosulfuric acid, diammonium salt
Molar mass 148.20 g/mol
Appearance Colorless crystalline solid
Odor Ammonia
Density 1.679 g/cm3 (at 25 °C)
Melting point 150 °C (302 °F; 423 K) (decomposition)
Boiling point Decomposes
Very soluble in cold water
1.033 g/ 100 ml (at 100 °C)
Solubility Slightly soluble in acetone
Insoluble in benzene, diethyl ether, ethanol, toluene
Safety data sheet Sigma-Aldrich
Lethal dose or concentration (LD, LC):
2,890 mg/kg (rat, oral)
Related compounds
Related compounds
Sodium thiosulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Ammonium thiosulfate is an inorganic compound with the formula (NH4)2S2O3.



Ammonium thiosulfate is a reducing agent, and is commonly used in gold and silver mining.

It tends to decompose to ammonium sulfite and sulfur at high temperatures.


Ammonium thiosulfate is a colorless crystalline solid, soluble in water but less soluble in organic solvents. It has a slight ammonia odor. Its decomposition is noticeable above 50 °C.


Ammnoium thiosulfate is sold as fertilizer, as aqueous solution. THIO-S is one such product. It contains 30-60% ammonium thiosulfate by mass. To obtain the pure compound, gently heat the solution for several hours at ~90 °C, then cool the concentrated solution to crystallize the compound.

Ammonium thiosulfate is also available as photographic fixer.


Ammonium thiosulfate can be produced by mixing two solutions of ammonium sulfate and sodium thiosulfate, followed by cooling, filtration of the sodium sulfate. The filtrate is concentrated and cooled to recrystallize the compound.


  • Reducing agent
  • Prevent the formation of dioxins and furans in coal wastes[1]
  • Fertilizer



Ammonium thiosulfate releases ammonia gas over time which is irritant.


In closed bottles, in well ventilated places. Storage temperature should be below 50 °C.


No special disposal is required, though it's best to strongly dilute it before pouring it down the drain or soil.



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