Difference between revisions of "Sodium thiosulfate"

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{{Chembox
 
{{Chembox
| Name =Sodium thiosulfate
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| Name = Sodium thiosulfate
 
| Reference =  
 
| Reference =  
| IUPACName =Sodium thiosulfate
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| IUPACName = Sodium thiosulfate
| PIN =
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| PIN =  
| SystematicName =Sodium thiosulfate
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| SystematicName = Sodium thiosulfate
| OtherNames = {{Unbulleted list
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| OtherNames = Sodium thiosulphate<br>Sodium hyposulfite<br>Hyposulphite of soda
  | ''Sodium thiosulphate''
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  | ''Sodium hyposulfite''
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  | ''Hyposulphite of soda''
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  }}
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<!-- Images -->
 
<!-- Images -->
| ImageFile =  
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| ImageFile = Sodium thiosulfate sample watchglass.jpg
| ImageSize =  
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| ImageSize = 300
 
| ImageAlt =  
 
| ImageAlt =  
 
| ImageName =  
 
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| ImageCaption = Sodium thiosulfate pentahydrate crystals
 
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| MeltingPt_ref =  
 
| MeltingPt_ref =  
 
| MeltingPt_notes = (pentahydrate)
 
| MeltingPt_notes = (pentahydrate)
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| Odor = Odorless
 
| pKa =  
 
| pKa =  
 
| pKb =  
 
| pKb =  
 
| Solubility = 70.1 g/100 mL (20 °C)<br>231 g/100 mL (100 °C)
 
| Solubility = 70.1 g/100 mL (20 °C)<br>231 g/100 mL (100 °C)
| SolubleOther =  
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| SolubleOther = Almost insoluble in [[acetonitrile]], [[ethanol]], [[methanol]]
 
| Solvent =  
 
| Solvent =  
| VaporPressure =  
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| VaporPressure = ~ 0 mmHg
 
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| Section3 = {{Chembox Structure
 
| Section3 = {{Chembox Structure
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| LD50 =  
 
| LD50 =  
 
| LC50 =  
 
| LC50 =  
| MainHazards =  
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| MainHazards = Irritant
 
| NFPA-F =  
 
| NFPA-F =  
 
| NFPA-H =  
 
| NFPA-H =  
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| OtherFunction =  
 
| OtherFunction =  
 
| OtherFunction_label =  
 
| OtherFunction_label =  
| OtherCompounds =  
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| OtherCompounds = [[Ammonium thiosulfate]]<br>[[Sodium metabisulfite]]<br>[[Sodium sulfite]]
 
   }}
 
   }}
 
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'''Sodium thiosulfate''' is an inorganic compound with the chemical formula Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub>. The solid is an efflorescent.
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'''Sodium thiosulfate''' is an inorganic compound with the chemical formula '''Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub>''', widely used in titrations and as cyanide poisoning antidote. The most common form of this salt is the pentahydrate '''Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub>·5H<sub>2</sub>O'''. This solid is slightly efflorescent.
  
 
==Properties==
 
==Properties==
 
===Chemical===
 
===Chemical===
 
Sodium thiosulfate reacts with acids, releasing sulfur, and sulfur dioxide fumes:
 
Sodium thiosulfate reacts with acids, releasing sulfur, and sulfur dioxide fumes:
:Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> + 2 HCl → 2 NaCl + S + SO<sub>2</sub> + H<sub>2</sub>O
 
  
When heated to 300 °C, sodium thiosulfate decomposes to [[sodium sulfate]] and sodium polysulfide:
+
: Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> + 2 HCl → 2 NaCl + S + SO<sub>2</sub> + H<sub>2</sub>O
  
:4 Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> → 3 Na<sub>2</sub>SO<sub>4</sub> + Na<sub>2</sub>S<sub>5</sub>  
+
The hydrated form has a low melting point of around 50 °C, but in fact it decomposes and the salt dissolves in its own water of crystallization. When heated more strongly, the water is driven off. When the anhydrous compound is heated to 300 °C, it decomposes to [[sodium sulfate]] and sodium polysulfide:
 +
 
 +
: 4 Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> → 3 Na<sub>2</sub>SO<sub>4</sub> + Na<sub>2</sub>S<sub>5</sub>
  
 
===Physical===
 
===Physical===
Sodium thiosulfate is an odorless white crystalline solid, soluble in water, but almost insoluble in alcohols.  
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Sodium thiosulfate pentahydrate is an odorless white crystalline solid, soluble in water, but almost insoluble in alcohols.  
  
 
==Availability==
 
==Availability==
Sodium thiosulfate is sometimes sold in pharmacies or pet stores.
+
Sodium thiosulfate pentahydrate is sold by many swimming pool suppliers, as "chlorine neutralizer", in solid form.
 +
 
 +
Sodium thiosulfate is sometimes sold in pharmacies or pet stores. It can be bought cheaply online.
  
 
==Preparation==
 
==Preparation==
Sodium thiosulfate can be prepared by boiling an aqueous [[sodium hydroxide]] solution with elemental [[sulfur]].
+
Sodium thiosulfate can be prepared by boiling an aqueous [[sodium hydroxide]] solution with elemental [[sulfur]], but isolation of the pure solid compound is not easy. The other reaction product is sulfide and polysulfide.
  
[[Sodium sulfite]] can also be used instead of sodium hydroxide.
+
[[Sodium sulfite]] can also be used instead of sodium hydroxide. In that case, the only reaction product is sodium thiosulfate.
  
 
==Projects==
 
==Projects==
 
*Iodine clock reaction
 
*Iodine clock reaction
*Neutralize bleach
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*Neutralize [[bleach]]
 
*Remove [[iodine]] stains
 
*Remove [[iodine]] stains
 
*Cyanide poisoning antidote
 
*Cyanide poisoning antidote
*Gold extraction
+
*[[Gold]] extraction
 
*Supercooling demonstration
 
*Supercooling demonstration
 
*Redox titrations
 
*Redox titrations
 
*Bunte salts synthesis
 
*Bunte salts synthesis
*Thioglycolic acid synthesis
+
*[[Thioglycolic acid]] synthesis
  
 
==Handling==
 
==Handling==
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===Storage===
 
===Storage===
In closed containers.
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Sodium thiosulfate should be kept in closed containers.
  
 
===Disposal===
 
===Disposal===
 +
No special precautions need to be taken. Bleach can be used to neutralize it.
  
 
==References==
 
==References==
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[[Category:Reducing agents]]
 
[[Category:Reducing agents]]
 
[[Category:Materials unstable in acidic solution]]
 
[[Category:Materials unstable in acidic solution]]
 +
[[Category:Readily available chemicals]]
 
[[Category:Materials available as food grade]]
 
[[Category:Materials available as food grade]]
 +
[[Category:Antidotes]]

Latest revision as of 22:41, 17 October 2020

Sodium thiosulfate
Sodium thiosulfate sample watchglass.jpg
Sodium thiosulfate pentahydrate crystals
Names
IUPAC name
Sodium thiosulfate
Systematic IUPAC name
Sodium thiosulfate
Other names
Sodium thiosulphate
Sodium hyposulfite
Hyposulphite of soda
Properties
Na2S2O3
Molar mass 158.11 g/mol (anhydrous)
248.18 g/mol (pentahydrate)
Appearance White crystalline solid
Odor Odorless
Density 1.667 g/cm3
Melting point 48.3 °C (118.9 °F; 321.4 K) (pentahydrate)
Boiling point 100 °C (pentahydrate) 320 °C (608 °F; 593 K) (decomposes)
70.1 g/100 mL (20 °C)
231 g/100 mL (100 °C)
Solubility Almost insoluble in acetonitrile, ethanol, methanol
Vapor pressure ~ 0 mmHg
Hazards
Safety data sheet MSDS
Flash point Non-flammable
Related compounds
Related compounds
Ammonium thiosulfate
Sodium metabisulfite
Sodium sulfite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium thiosulfate is an inorganic compound with the chemical formula Na2S2O3, widely used in titrations and as cyanide poisoning antidote. The most common form of this salt is the pentahydrate Na2S2O3·5H2O. This solid is slightly efflorescent.

Properties

Chemical

Sodium thiosulfate reacts with acids, releasing sulfur, and sulfur dioxide fumes:

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

The hydrated form has a low melting point of around 50 °C, but in fact it decomposes and the salt dissolves in its own water of crystallization. When heated more strongly, the water is driven off. When the anhydrous compound is heated to 300 °C, it decomposes to sodium sulfate and sodium polysulfide:

4 Na2S2O3 → 3 Na2SO4 + Na2S5

Physical

Sodium thiosulfate pentahydrate is an odorless white crystalline solid, soluble in water, but almost insoluble in alcohols.

Availability

Sodium thiosulfate pentahydrate is sold by many swimming pool suppliers, as "chlorine neutralizer", in solid form.

Sodium thiosulfate is sometimes sold in pharmacies or pet stores. It can be bought cheaply online.

Preparation

Sodium thiosulfate can be prepared by boiling an aqueous sodium hydroxide solution with elemental sulfur, but isolation of the pure solid compound is not easy. The other reaction product is sulfide and polysulfide.

Sodium sulfite can also be used instead of sodium hydroxide. In that case, the only reaction product is sodium thiosulfate.

Projects

  • Iodine clock reaction
  • Neutralize bleach
  • Remove iodine stains
  • Cyanide poisoning antidote
  • Gold extraction
  • Supercooling demonstration
  • Redox titrations
  • Bunte salts synthesis
  • Thioglycolic acid synthesis

Handling

Safety

Sodium thiosulfate may cause irritation on contact.

Storage

Sodium thiosulfate should be kept in closed containers.

Disposal

No special precautions need to be taken. Bleach can be used to neutralize it.

References

Relevant Sciencemadness threads