Testing for Common Gases

• Carbon Dioxide:

  • The test for carbon dioxide involves bubbling the gas through an aqueous solution of calcium hydroxide (limewater)
  • If the gas is carbon dioxide, the limewater turns milky or cloudy
• Diagram showing the test for carbon dioxide gas:

  
• Hydrogen:

  • The test for hydrogen is often referred to as the 'squeaky pop' test
  • The test for hydrogen consists of holding a burning splint held at the open end of a test tube of gas
  • If the gas is hydrogen it burns with a loud “pop” sound which is the result of the rapid combustion of hydrogen with oxygen to produce water
  • Be sure not to insert the splint right into the tube, just at the mouth, as the gas needs air to burn
• Diagram showing the test for hydrogen gas:

  
• Oxygen:

  • The test for oxygen consists of placing a glowing splint inside a test tube of gas
  • If the gas is oxygen the splint will relight
• Diagram showing the test for oxygen gas:

  
• Chlorine:

  • The test for chlorine makes use of litmus paper
  • If chlorine gas is present, damp blue litmus paper will be bleached white
  • It may turn red briefly before bleaching, as acids are produced when chlorine comes into contact with water
  • Chlorine should always be handled in a fume cupboard due to its toxicity
• Diagram showing the test for chlorine gas: