Potassium thiosulfate

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Potassium thiosulfate
Names
Other names
  • Dipotassium monothiosulfate
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.030.593 Edit this at Wikidata
EC Number
  • 233-666-8
UNII
  • InChI=1S/2K.H2O3S2/c;;1-5(2,3)4/h;;(H2,1,2,3,4)/q2*+1;/p-2
    Key: FGRVOLIFQGXPCT-UHFFFAOYSA-L
  • [O-]S(=O)(=S)[O-].[K+].[K+]
Properties
K2S2O3
Molar mass 190.32 g/mol
Appearance White solid
Density 2.37 g/cm3
96.1 g/100 ml (0 °C)
155.4 g/100 ml (20 °C)
165 g/100 ml (25 °C)
175.7 g/100 ml (30 °C)
204.7 g/100 ml (40 °C)
215.2 g/100 ml (50 °C)
238.3 g/100 ml (60 °C)
255.2 g/100 ml (70 °C)
293.1 g/100 ml (80 °C)
312 g/100 ml (90 °C)[1]
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319
P264, P280, P302+P352, P305+P351+P338, P321, P332+P313, P337+P313, P362
Related compounds
Other anions
 Potassium sulfite; Potassium sulfate
Other cations
 Sodium thiosulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Potassium thiosulfate is an inorganic compound with the formula K2S2O3. This salt can form multiple hydrates, such as the monohydrate, dihydrate, and the pentahydrate, all of which are white or colorless solids.[1] It is used as a fertilizer.

Formation and reactions

Main article: Thiosulfate

Thiosulfate salts are produced by the reaction of

ammonium hydroxide, sulfur dioxide, and elemental sulfur.[2] Thiosulfates are stable in neutral or alkaline solutions, but not in acidic solutions, due to disproportionation to sulfur dioxide and sulfur:[3]

S
2O2−
3 + 2 H+ → SO2 + "S" + H2O

Due to this property, it can sequester metals, especially iron.[2]

Thiosulfate reacts with iodine to give tetrathionate, in this case potassium thiosulfate reacts with iodine to produce potassium tetrathionate and potassium iodide:

2 K2S
2O
3 + I2 → K2S
4O
6 + 2 KI

Thiosulfate extensively forms diverse complexes with transition metals. In the era of silver-based photography, thiosulfate was consumed on a large scale as a "stop" reagent. This application exploits thiosulfate's ability to dissolve silver halides. Thiosulfate is also used to extract or leach gold (sodium thiosulfate) and silver from their ores as a less toxic alternative to cyanide.[3]

Uses

Potassium thiosulfate is commonly used as a fertilizer alone or with

fumigants being released from the soil.[6] If used alone it is used in very dilute solution due to its ability to cause phytotoxicity symptoms. This is caused by the elemental sulfur being oxidized to produce sulfuric acid.[4]

References

  1. ^ a b Atherton Seidell (1919). Solubilities of inorganic and organic compounds c. 2. D. Van Nostrand Company. p. 568.
  2. ^
    ISBN 978-3-030-59197-7
    . Retrieved 6 October 2021.
  3. ^
    ISBN 978-3527306732
    .
  4. ^
    ISBN 978-1-4786-3884-1
    . Retrieved 6 October 2021.
  5. PMID 29128773
    .
  6. PMID 18440581
    .
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