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Green flame

Question:  How come when you heat ammonium chloride and boric acid crystals 
over and open flame the flame turns green?
From Ryan Simmons

Answer:
I tried your mixture.  I also tried NH4Cl and H3BO3 individually.
The NH4Cl burned with no apparent color while the H3BO3 burned green.
My conclusion would be:  the element boron, when its electrons are
excited, will emit visible light in the 500 nanometer range (green light)
when those electrons relax to lower energy levels.  For a more detailed
explanation (somewhat) of this phenomenon, see the chemistry archives
section for the question on fireworks.
-Joe Schultz

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