Ammonium thiosulfate

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Ammonium thiosulfate
Names
IUPAC name
Diammonium thiosulfate
Other names
Ammonium thiosulphate
Thiosulfuric acid, ammonium salt (1:2)
Thiosulfuric acid, diammonium salt
Properties
H8N2O3S2
(NH4)2S2O3
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
Hazards
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.

Properties

Chemical

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.

Physical

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.

Availability

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.

Preparation

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.

Projects

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

Handling

Safety

Ammonium thiosulfate releases ammonia gas over time which is irritant.

Storage

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

Disposal

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

References

  1. http://www.mzp.cz/ris/vis-edice.nsf/5262baa1b2012f9cc125723b003a63ed/67c5ee6df3296b54c1257419002c2769?OpenDocument&ExpandSection=17

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