Collecting Gases

Methods for Collecting Gases

Displacement of water

• Collects gases that are insoluble to slightly soluble in water.
• Collecting: Carbon dioxide, hydrogen, oxygen

Downward Delivery

• Used to collect gases that are soluble in water and denser than air.
• Collecting: Chlorine, Hydrogen Chloride, Sulfur dioxide

Upward Delivery

• Used to collect gases that are soluble in water and less dense than air
• Collecting: Ammonia

Drying agents 

Fused Calcium Chloride

• For drying most gases, except for ammonia which can react with calcium chloride.

Concentrated Sulfuric Acid

• For drying neutral gases such as hydrogen, acidic gases such as chlorine, hydrogen chloride, and sulfur dioxide.
• It cannot be used for drying alkaline gases.

Quicklime (calcium oxide)

• For drying alkaline gases such as ammonia.
• Cannot be used to dry acidic gases.