Difference between revisions of "Potassium bisulfite"

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(Created page with "{{distinguish|potassium metabisulfite}} {{Chembox | Name = Potassium bisulfite | Reference = | IUPACName = Potassium hydrogen sulfite | PIN = | SystematicName = | OtherNames =...")
 
 
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| MeltingPt_ref =  
 
| MeltingPt_ref =  
 
| MeltingPt_notes = (decomposes)
 
| MeltingPt_notes = (decomposes)
| Odor = Sulfur dioxide
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| Odor = Sulfurous
 
| pKa =  
 
| pKa =  
 
| pKb =  
 
| pKb =  
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==Properties==
 
==Properties==
 
===Chemical===
 
===Chemical===
Potassium bisulfite oxidizes in air to [[potassium bisulfate]]. Addition of a base raises the pH, converting the compound in [[potassium sulfite]].
+
Potassium bisulfite oxidizes in air to [[potassium bisulfate]].
 +
 
 +
: KHSO<sub>3</sub> + ½ O<sub>2</sub> → KHSO<sub>4</sub>
 +
 
 +
The reaction occurs faster if water is present.
 +
 
 +
Addition of a base raises the pH, converting the compound in [[potassium sulfite]].
 +
 
 +
: KHSO<sub>3</sub> + KOH → K<sub>2</sub>SO<sub>3</sub> + H<sub>2</sub>O
 +
 
 +
Evaporating an aq. solution of potassium bisulfite saturated with [[sulfur dioxide]] yields [[potassium metabisulfite]]:
 +
 
 +
:2 KHSO<sub>3</sub> ⇌ H<sub>2</sub>O + K<sub>2</sub>S<sub>2</sub>O<sub>5</sub>
  
 
===Physical===
 
===Physical===
Potassium bisulfite is a white solid
+
Potassium bisulfite is a white solid, with a sulfurous smell, soluble in water.
  
 
==Availability==
 
==Availability==
It is sold as both solid and solution.
+
Potassium bisulfite is sold as both solid and solution, with the latter being more available. Make sure to check the product label/designation, as some products labeled as potassium bisulfite are actually [[potassium metabisulfite]].
  
It is available as the food additive E228.
+
It is available as the food additive '''E228'''.
  
 
==Preparation==
 
==Preparation==
Can be prepared by bubbling and excess of [[sulfur dioxide]] through a solution of [[potassium carbonate]] or [[potassium hydroxide]].
+
Can be prepared by bubbling and excess of [[sulfur dioxide]] through a solution of [[potassium carbonate]] or [[potassium hydroxide]]. The excess sulfur dioxide is removed, usually by adding KOH until the right pH, then the solution is dried in an airless atmosphere, to prevent the sulfite from oxidizing to sulfate.
 +
 
 +
: K<sub>2</sub>CO<sub>3</sub> + SO<sub>2</sub> → K<sub>2</sub>SO<sub>3</sub> + H<sub>2</sub>O + CO<sub>2</sub>
 +
: 2 KOH + SO<sub>2</sub> → K<sub>2</sub>SO<sub>3</sub> + H<sub>2</sub>O
  
 
==Projects==
 
==Projects==
 
*Reducing agent
 
*Reducing agent
*Make potassium bisulfate
+
*Make sulfur dioxide
 +
*Make [[potassium bisulfate]]
 +
*Make [[hydroxylamine]]
  
 
==Handling==
 
==Handling==
 
===Safety===
 
===Safety===
Potassium bisulfite releases toxic sulfur dioxide gas. Work in a well ventilated area or fumehood.
+
Potassium bisulfite releases toxic sulfur dioxide gas, especially in contact with acids. Work in a well ventilated area or fumehood.
  
 
===Storage===
 
===Storage===
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===Disposal===
 
===Disposal===
Can be neutralized with bleach or hydrogen peroxide
+
Can be neutralized with bleach or hydrogen peroxide, then with a base to potassium sulfate.
  
 
==References==
 
==References==
 
<references/>
 
<references/>
 
===Relevant Sciencemadness threads===
 
===Relevant Sciencemadness threads===
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=155732 Bisulfite adduct and reagents?]
  
 
[[Category:Chemical compounds]]
 
[[Category:Chemical compounds]]
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[[Category:Reducing agents]]
 
[[Category:Reducing agents]]
 
[[Category:Materials unstable in acidic solution]]
 
[[Category:Materials unstable in acidic solution]]
 +
[[Category:Irritants]]
 +
[[Category:Air-sensitive materials]]

Latest revision as of 09:42, 25 June 2023

Not to be confused with potassium metabisulfite.
Potassium bisulfite
Names
IUPAC name
Potassium hydrogen sulfite
Other names
E228
Monopotassium sulfite
Potassium bisulphite
Sulfurous acid, monopotassium salt
Properties
KHSO3
Molar mass 120.1561 g/mol
Appearance White crystalline powder
Odor Sulfurous
Melting point 190 °C (374 °F; 463 K) (decomposes)
Boiling point Decomposes
49 g/100 mL (20 °C)
115 g/100 mL (100 °C)
Solubility Insoluble in alcohols, benzene, toluene
Hazards
Safety data sheet CAMEO (solution)
Flash point Non-flammable
Related compounds
Related compounds
Potassium sulfite
Potassium bisulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium bisulfite or potassium hydrogen sulfite is a chemical compound with the chemical formula KHSO3. The compound is commonly used in food industry, for sterilizing wine, as food additive E228. While it can be found as solid, it is more commonly encountered as solution.

Properties

Chemical

Potassium bisulfite oxidizes in air to potassium bisulfate.

KHSO3 + ½ O2 → KHSO4

The reaction occurs faster if water is present.

Addition of a base raises the pH, converting the compound in potassium sulfite.

KHSO3 + KOH → K2SO3 + H2O

Evaporating an aq. solution of potassium bisulfite saturated with sulfur dioxide yields potassium metabisulfite:

2 KHSO3 ⇌ H2O + K2S2O5

Physical

Potassium bisulfite is a white solid, with a sulfurous smell, soluble in water.

Availability

Potassium bisulfite is sold as both solid and solution, with the latter being more available. Make sure to check the product label/designation, as some products labeled as potassium bisulfite are actually potassium metabisulfite.

It is available as the food additive E228.

Preparation

Can be prepared by bubbling and excess of sulfur dioxide through a solution of potassium carbonate or potassium hydroxide. The excess sulfur dioxide is removed, usually by adding KOH until the right pH, then the solution is dried in an airless atmosphere, to prevent the sulfite from oxidizing to sulfate.

K2CO3 + SO2 → K2SO3 + H2O + CO2
2 KOH + SO2 → K2SO3 + H2O

Projects

Handling

Safety

Potassium bisulfite releases toxic sulfur dioxide gas, especially in contact with acids. Work in a well ventilated area or fumehood.

Storage

Should be stored in closed, air-tight bottles.

Disposal

Can be neutralized with bleach or hydrogen peroxide, then with a base to potassium sulfate.

References

Relevant Sciencemadness threads