Specialty Chemistry Forums > Citizen Chemist

colors in inorganic elements

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movies:
A gas could emit in different parts of the visible spectrum though, so there could be multiple colors, right?  You can only get one color per transition though.

Corvettaholic:
So if a gas is emitting in different parts of the visible spectrum at the same time, why is it that we can only see one color at a time? Lets take a look at neon signs, do they use exclusively neon? If a gas can only give off one color, they can't all be neon because there are different colors in the signs... or is colored glass? So lets say you have a tube of nitrogen and it gives color x, but you want to see color y. How do you get color y to show up as opposed to color x?

movies:
In "neon" signs I think they use different gases to get the different colors.

Corvettaholic:
You know, I think you're right. I remember reading some article on neon signs. If you look at one up close, you'll notice small little sections with no color that are in the tube. I imagine that part seperates one tube into two, which allows containment of 2 different gasses. I'd also wager a guess that the high voltage that powers the tube, somehow gets passed along to the next gas tube. How? Dunno. Maybe inductance or a small conductor I can't see.

If I can figure out how to get more than one color out of a specific gas, I'll be sure to let you all know!

jdurg:
Correct.  Sadly, the term 'Neon Sign' has become used to describe ANY gas discharge tube used for signage.  Those tubes can contain anything from sodium vapor, mercury vapor, argon, nitrogen, xenon, neon, etc. etc.  Any one particular gas will only emit one specific color unless different filters are used.  Let's take Neon, for example.  Put low pressure neon gas in a discharge tube and apply some voltage, and you'll see the distinct bright-red color of Neon.  However, Neon's emission spectrum also includes wavelengths of other colors.  So if you could filter off the red color, you may be able to see the other ones.  So if you had a tube which was lined with a compound that absorbed red light but allowed other colors to go through, that 'Neon' gas would look either bluish or yellow.  So a gas does produce more than one color, however the color we see is due to a greater intensity of said color.  (Like in neon, the reds and oragnes are a higher intensity and more prevalent than the blues and yellows, so to us Neon gas has a red-orange color).


So the only way to get multiple colors out of a single gas is to use filters or special coatings on the tubes.

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