Re: Hydrogen flame: Thermocouple

From: G. R. L. Cowan (gcowan_at_eagle.ca)
Date: 12/22/04 

Date: Wed, 22 Dec 2004 15:41:48 -0500

H2O wrote:
>
> I've been trying to make little amounts of electricity using a thermocouple,
> and hydrogen stored in a testube.
> But, when I measure the voltage on the other end with a voltmeter, the
> needle doesn' t even move.
> I don't think I'm burning the hydrogen right, as there are no signs of the
> heat. All I do is put a flame near the mouth, and nothing happens,

As a child I burned hydrogen by catching it underwater,
over the electrode producing it, in an inverted drinking glass --
one with a conical shape, widening towards the top,
as I thought a cylinder might burst and throw glass --
bringing the inverted glass up out of the water,
still inverted, next to a match.

It made a high-pitched little bark.
It's *very* easy to light, and small, unpressurized volumes of it
like this burn up completely in a fraction of a second.

If your test tubes aren't barking,
there's a good chance all the hydrogen is escaping them
before you get around to trying to light them.
Just keeping the glass inverted isn't enough,
unless you're very quick. The hydrogen diffuses *rapidly*
downward into room air.

Even if they did bark, the heat driving that expansion
is very little, because uncompressed hydrogen has an exceedingly
low energy density. You'd be better off heating your thermocouple's
hot junction with a candle. Still burning hydrogen,
but burning carbon at the same time, a much safer
and more practical approach.

If you attempt to burn a continuing flow of hydrogen,
not just a few mL in a test tube,
and find yourself numb all down one side,
deaf in the ear on that side,
and lying on the floor, you probably aren't having a stroke.

--- Graham Cowan, former hydrogen fan
http://www.eagle.ca/~gcowan/Paper_for_11th_CHC.html --
how individual mobility gains nuclear cachet

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