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Author Topic: Metal Halides  (Read 3314 times)

Offline Fuzzy Logic

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Metal Halides
« on: 09/08/2006 21:39:09 »
I have an interest in electronics,  and stubled across a page in wikipedia about metal halide lamps,  i was wondering exactly which metal halides were used to produce each different colout temperature.  I was trying to think back to my old school days and which metasl burned which colour,  I know sodium burns yellow,  copper burns green and i think potassium burns violet,  but i was wondering what metal would be used to  produce a blue light.


 

Offline Fuzzy Logic

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Re: Metal Halides
« Reply #1 on: 09/08/2006 21:40:12 »
sorry bout double post btw [:I]
 

another_someone

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Re: Metal Halides
« Reply #2 on: 10/08/2006 00:12:18 »
I don't believe metal halide lamps are about creating colour, they are about increasing the intensity of the lamp by raising its temperature while allowing an adequate life for the bulb.

http://home.howstuffworks.com/question151.htm
quote:

Let's start with a normal electric light bulb like you see in any normal household lamp. A normal light bulb is made up of a fairly large, thin, frosted glass envelope. Inside the glass is a gas such as argon and/or nitrogen. At the center of the lamp is a tungsten filament. Electricity heats this filament up to about 4,500 degrees F (2,500 degrees Celsius). Just like any hot metal, the tungsten gets "white hot" at that heat and emits a great deal of visible light in a process called incandescence. See How Gas Lanterns Work for more information on incandescence.
A normal light bulb is not very efficient, and it only lasts about 750 to 1,000 hours in normal use. It's not very efficient because, in the process of radiating light, it also radiates a huge amount of infrared heat -- far more heat than light. Since the purpose of a light bulb is to generate light, the heat is wasted energy. It doesn't last very long because the tungsten in the filament evaporates and deposits on the glass. Eventually, a thin spot in the filament causes the filament to break, and the bulb "burns out."
A halogen lamp also uses a tungsten filament, but it is encased inside a much smaller quartz envelope. Because the envelope is so close to the filament, it would melt if it were made from glass. The gas inside the envelope is also different -- it consists of a gas from the halogen group. These gases have a very interesting property: They combine with tungsten vapor. If the temperature is high enough, the halogen gas will combine with tungsten atoms as they evaporate and redeposit them on the filament. This recycling process lets the filament last a lot longer. In addition, it is now possible to run the filament hotter, meaning you get more light per unit of energy. You still get a lot of heat, though; and because the quartz envelope is so close to the filament, it is extremely hot compared to a normal light bulb.





George
 

Offline Fuzzy Logic

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Re: Metal Halides
« Reply #3 on: 10/08/2006 14:13:27 »
I was actually refering to high intensity discharge lamps,  not tungsten halogen lamps.... like these:

newbielink:http://www.bulbman.com/index.php?main_page=index&cPath=4603 [nonactive]
 

Offline lightarrow

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Re: Metal Halides
« Reply #4 on: 10/08/2006 14:32:06 »
quote:
Originally posted by Fuzzy Logic

I was actually refering to high intensity discharge lamps,  not tungsten halogen lamps.... like these:

http://www.bulbman.com/index.php?main_page=index&cPath=4603



Very interesting, it's the first time I know of such kind of lamps.
Probably, to know how to make a blue color, we should ask a fireworks expert, the principle should be the same. If I remember correctly, in fireworks a blue colour (which is very difficult to obtain) is achieved, for example, with copper compounds, or (more expensive) with indium compounds.
 

another_someone

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Re: Metal Halides
« Reply #5 on: 10/08/2006 16:50:01 »
Apologies about the misunderstanding.



George
 

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Re: Metal Halides
« Reply #5 on: 10/08/2006 16:50:01 »

 

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