Carbon dioxide was discovered in the early seventeenth century by the Flemish Jan Baptista, who called it "sylvester gas".

Carbon dioxide or carbonic acid gas (chemical formula CO₂) is a colorless and odorless, natural gas present in the atmosphere.

Carbon dioxide exists in three forms:

• as a liquid
• as a gas
• as a solid (=dry ice)

Because of its typical chemical and physical properties, CO₂ plays an important role in many applications.

Physical properties:

• colorless
• inert, non-flammable
• odorless
• taste: neutral
• non-toxic
• bacteriostatic

Density CO₂ /air: 1,529 (1.5 times heavier than air)
Molecular weight: 44,011 kg/mol
Normal density: 1,977 kg/m³

Some typical properties:

• CO₂ cannot exist as a liquid in open air
  (at atmospheric pressure).
• CO₂ cannot be liquefied at temperatures above 31°C.
• Dry ice sublimates to CO₂ gas at atmospheric pressure.
• CO₂ becomes "supercritical" at temperatures above 31°C.