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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Zensation on May 15, 2014, 10:31:02 PM

Title: Halide/hg Bulbs for photochemistry, from hardware store?
Post by: Zensation on May 15, 2014, 10:31:02 PM

I understand the importance of the bulb having quartz components to allow UV passage, but the one thing I am not finding any information on, is whether or bulbs from the hardware store are naturally made with quartz?

To clarify, I look online and see the UV spectrum from various bulbs, low pressure mercury, medium pressure mercury, etc. These all output partially in the UV range. Though, why do some bulbs specifically say they are made with quartz, when others (at the hardware store) make no specification? If I get a medium or low pressure mercury bulb from home depot will it still have the UV properties that I am looking for?

Title: Re: Halide/hg Bulbs for photochemistry, from hardware store?
Post by: Hunter2 on May 16, 2014, 05:42:51 AM

I think the UV part will be converted with the white layer of the insidewall of the bulb. Otherwise you get sun burn if you have that radiation to your skin.

Title: Re: Halide/hg Bulbs for photochemistry, from hardware store?
Post by: Zensation on May 16, 2014, 02:13:08 PM

Not all bulbs have that white layer. Many of them are just completely clear, which are the ones I am referring to.

Title: Re: Halide/hg Bulbs for photochemistry, from hardware store?
Post by: Hunter2 on May 17, 2014, 03:50:43 PM

But these ones will not contain mercury and will not emitt UV.

Title: Re: Halide/hg Bulbs for photochemistry, from hardware store?
Post by: Zensation on May 17, 2014, 06:20:01 PM

I'm pretty sure the Mercury Bulbs do contain mercury... though I do believe the ones at the hardware store are all High Pressure, for normal lighting circumstances, and those do not emit much UV.

I am not sure why but I cannot find any Medium or Low pressure mercury bulbs that are in the shape of normal bulbs. All of them come as long tubes. I'm not sure what difference inside the bulbs besides the pressure disallows the medium or low pressure ones from being made in normal bulb shapes.

Title: Re: Halide/hg Bulbs for photochemistry, from hardware store?
Post by: Enthalpy on May 27, 2014, 06:44:46 AM

The electric field that makes an arc diminishes at low pressure (but there's a minimum), so that for a given voltage, a low-pressure arc is longer.

Within some pressure range, it takes a fixed voltage drop per electron-molecule collision to sustain the ionization.

By the way, all fluorescent bulbs from the supermarket are semi-long tubes folded to fit in the usual pear shape and in a convenient size.