MJ> If you have
MJ> ever seen a burnt-out light bulb, the black coating on the inside is
MJ> tungsten that was vaporized by overheating.
G’day; another 0.02 from me. Tne main reason why light bulbs
fail is due to (a) the tungsten filament very slowly vapourising,
and thus making it have a higher resistance to the current, and
(b) oxygen from the atmosphere gettng in and oxidising the
tungsten. Most of the bulb-blackening is tungsten oxide which is
far more volatile than tungsten. Long ago I used to make
tungsten/molybdenum thermocouples for temperature measurement in
high temperature furnaces, and they had to be sealed into pure
otherwise they’d soon become oxidised and last no time at all.
So, when you heat a tungsten pick white-hot, don’t do it for very
long. Cheers, –
/\ / / John Burgess, / / / //\ @John_Burgess2 / / \ \