Why do gas flames sparkle yellow when water falls on it?

The domestic LPG which is a mixture of saturated hydrocarbons (alkenes) like Propane and Butane burns with a hotter blue flame due to better combustion reaction. But we might have observed that it sparkles in yellow whenever a few water droplets fall on the burner. Why? Is it because of water or the gas?

• The water we generally use has a high concentration of Sodium Chloride (Common salt) in it. When water falls on the burning gas flame, the excited electrons in Sodium ions come back to the ground state with the release of photons that correspond to yellow colour and we can also see white spots on the burner due to settling of these salt particles.
  
  
• Sodium vapors are the reason for the yellow color of many street lights and flood lights that we regularly see around.

                                                                                   Hemachandra K
                                                                                     Research Scholar, TIFR, Mumbai

Published date : 27 Apr 2013 06:46PM