Sulfur dioxide

 

Sulfur dioxide

Chemical formula	SO2
OTP appearance	colorless noxious gas
Molar Mass(g/mol)	64.066
Density(g/cc)	0.0026288
Melting Point(°C)	-72
Boiling Point(°C)	-10
Solubility in water(g/L)	94
Speed of sound 20°C, 1atm (m/s)	201
Immediate Danger to Life and Health	100ppm
NFPA 704	2 3 0

Uses

The primary use of sulfur dioxide is as a feedstock for sulfuric acid via sulfur trioxide. Heavier than air.

Natural occurence

• Sulfur dioxide occurs naturally in volcanic vents and sulfur springs

Hazards

• Inhalation of large amounts of sulfur dioxide can result in pulmonary edema, which (according to ) is treated with supportive care for breathing and heart issues.

Production

Synthesis

There are many ways to produce sulfur dioxide depending on the raw materials available. Each of the below produces approximately 1 mol of sulfur dioxide:

from Sulfur

Molten sulfur combines with air almost quantitatively producing sulfur dioxide, most efficiently by spraying fine droplets of molten sulfur into preheated (120°C) air:

• S₈ + 8 O₂ → 8 SO₂

Thermal decomposition of mineral sulfides and sulfates

• Roast 1 mol (240g) of galena in air at 1000°C

  2 PbS + 3 O₂ → 2 PbO + 2 SO₂

• Roast 1/2 mol (60g) of iron pyrite in air

  4 FeS₂ + 11 O₂ → 2 Fe₂O₃ + 8 SO₂

• Roast 5/6 mol (113.3g) of gypsum and 1/6 mol (20g) of iron pyrite with 1/2 mol (30g) of silicon dioxide

  10 CaSO₄ + 2 FeS₂ + 6 SiO₂ → Fe₂SiO₄ + 5 Ca₂SiO₄ + 14 SO₂

  This has the interesting characteristic of requiring no external oxygen source

  The fayelite (Fe₂SiO₄) can be oxidized further to magnetite and silicon dioxide

  The calcium silicate Ca₂SiO₄ can be used as a fire retardant

NaSO

sodium sulfite

Very roughly, 1ubm of sulfite to 2 ubm of commercial or 1:3 of azeotropic HCl produces SO2

1. Gather 126ubm (1M) sodium sulfite
2. Gather 500ubm of water
3. Gather 255ubm (222ml, 2M) of commercial (30%-ish, 9M) hydrochloric acid

   or 365ubm (333ml, 2M) of azeotropic (20.2%, 6M) hydrochloric acid

4. Completely dissolve the sodium sulfite in the water.
5. Drip hydrochloric acid into sodium sulfite solution producing 2 mols of salt, 1 mol of water, and 1 mol of sulfur dioxide

   Na₂SO₃ + 2 HCl → 2 NaCl + SO₂ + H₂O

sodium metabisulfite

• Drip Hydrochloric acid onto Sodium metabisulfite

  Na₂S₂O₅ + 2 HCl → 2 NaCl + H₂O + 2 SO₂

Purification

• Sulfur dioxide is only slightly soluble in water, whereas sulfur trioxide reacts, and carbon dioxide is very soluble. Bubbling through warm water, therefore, will remove the bulk of these compounds.

Testing

• A paper strip made with a solution of potassium permanganate will rapidly turn from purple to brown in the presence of sulfur dioxide
• Sulfur dioxide will decolor a solution of potassium permanganate rapidly

Storage

• A practical way to contain and store sulfur dioxide effluent is to combine it with sodium hydroxide, producing sodium bisulfite. Sodium bisulfite is readily convertible back to sulfur dioxide by adding almost any acid.

  SO₂(g) + NaOH(aq) → NaHSO₃ // put

  NaHSO₃ + HCl → NaCl + H₂O(l) + SO₂(g) // get

Disposal

• Burn with hydrogen sulfide producing elemental sulfur and water

  SO₂ + 2 H₂S → 2 H₂O + 3 S

• Bubble through a solution of potassium permanganate

  5 SO₂ + 2 KMnO₄ + 2 H₂O → 2 H₂SO₄ + 2 MnSO₄ + K₂SO₄

See Also

• Sulfuric acid
• Chamber process