Oleum Gas

Source: NDTV

Subject: Science and Technology

Context: A major oleum gas leak at Bhageria Industries Ltd in Boisar, Maharashtra, forced the evacuation of over 2,000 residents, including 1,600 students.

About Oleum Gas:

What it is?

• Oleum, commonly referred to as fuming sulfuric acid, is a highly corrosive chemical consisting of dissolved sulfur trioxide (SO₃) in concentrated sulfuric acid (H₂SO₄). It releases dense white fumes when exposed to moist air.

Chemical Name:

• Oleum (Fuming Sulfuric Acid)
• Chemical representation: H₂SO₄·xSO₃
• When x = 1, the compound is Disulfuric Acid (H₂S₂O₇), also called Pyrosulfuric Acid

Production:

Oleum is produced through the Contact Process, which involves:

1. Burning sulfur to produce sulfur dioxide (SO₂).
2. Oxidizing SO₂ to sulfur trioxide (SO₃).
3. Absorbing SO₃ into concentrated sulfuric acid to form oleum.

This method avoids directly dissolving SO₃ in water, which would create an uncontrollable acid mist.

Properties of the Gas:

• Physical Properties:
  • Appearance: It appears as dense, white cloudish smoke when leaked into the air.
  • Freezing Point: Its freezing point varies strongly with concentration; it can be solid at room temperature or remain liquid as low as zero degree.
• Chemical Properties:
  • Dehydration: It is an extremely strong dehydrating agent, capable of pulling water elements out of sugars to leave pure carbon (the carbon snake reaction).
  • Corrosivity: It is highly corrosive but lacks free water to attack surfaces, making it less corrosive to certain metals in its pure form compared to diluted acid.
  • Hydration: It has a very high enthalpy of hydration; when SO₃ in oleum meets water/moisture, it forms a fine mist of sulfuric acid.

Impact on Health:

• Acute Irritation: Exposure can cause minor to severe eye irritation.
• Respiratory Distress: Hazardous fumes can cause irritation to the respiratory tract; emergency responders use Self-Contained Breathing Apparatus (SCBA) to avoid inhalation.
• Sulfuric Acid Mist: In large releases, it creates a mist of micrometre-sized sulfuric acid particles that are hazardous over wide areas.

Applications:

• Sulfuric Acid Manufacture: Used as an intermediate to produce concentrated sulfuric acid by dissolving SO₃ without creating difficult-to-manage mists.
• Explosives: Used in manufacturing explosives like Trinitrotoluene (TNT) to create anhydrous nitration mixtures.
• Organic Chemistry: Acts as a harsh reagent for secondary nitration of nitrobenzene.
• Industrial Transport: Transported in rail tank cars as a safe way to move sulfuric acid compounds between refineries and consumers.