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Path: utzoo!watmath!clyde!cbosgd!cbdkc1!desoto!cord!bentley!hoxna!houxm!mhuxj!aluxe!2141smh
From: 2141smh@aluxe.UUCP (S. M. Henning,)
Newsgroups: net.consumers
Subject: Re: Lifetime Lightbulbs
Message-ID: <700@aluxe.UUCP>
Date: Thu, 7-Feb-85 16:06:24 EST
Article-I.D.: aluxe.700
Posted: Thu Feb  7 16:06:24 1985
Date-Received: Sat, 9-Feb-85 09:32:03 EST
References: <1516@hplabs.UUCP> <517@houxu.UUCP> <8054@brl-tgr.ARPA>
Organization: AT&T Bell Laboratories, Allentown, PA
Lines: 8

> Also, the tungsten actually boils off.  If we fill the bulbs with
> a halogen we can get the tungsten deposited back on the filiment.
> I used to be able to explain how this works, but I've forgotten.
>
The tungsten forms a tungsten-halide at lower intermediate temperatures.
The tungsten-halide is a gas and carries the gas back to the filament
where the heat decomposes the tungsten halide into tungsten which is 
deposited on the filament and halogen gas which free to do it again as needed.