From: REMOVE_THISdwilkins@means.net (Don Wilkins)
Newsgroups: rec.crafts.metalworking
Subject: Re: Why does my copper have gas?
Date: Fri, 02 Apr 1999 17:16:24 GMT

On Wed, 31 Mar 1999 23:07:55 GMT, eric@iptcorp.com (Eric Wilner)
wrote:

>pkoning@xedia.com (Paul Koning) writes:
><snip>
>: Oh yes, nitrogen dissolves in your blood, so sudden pressure drops
>: are nasty -- "the bends".  But that's not poisoning, it's plain old
>: physics.
>
>Actually, dissolving enough nitrogen in one's blood (under sufficient
>pressure) will cause "nitrogen narcosis" -- sounds like a toxic
>effect to me.  Takes kinda exceptional conditions...

Scuba diving may be an exceptional condition but it is a known problem
for divers. The result is a euphoria in which the diver does
irrational things such as ripping off their mask, suddenly diving too
deep, suddenly rushing to the surface, or other self-destructive
activity. Sort of like a teenager behind the wheel of a high-powered
auto (invincible).

This is the reason they change the composition of the air supply for
deep dives. Some of the nitrogen is replaced by helium e.g.


>Also, "used" nitrogen which has reacted with oxygen in the melt
>may be turning up as various oxides, most of which are quite
>toxic.  On the other hand, the concentration of oxides of
>nitrogen ought to be pretty low, unless the metal was just
>_loaded_ with oxygen.

I would not expect much reaction between oxygen and nitrogen at these
temperatures.

>(I don't recall what temperature is required to make nitrogen
>react with oxygen, as opposed to merely carrying it off.  It's
>within the range of combustion temperatures in an automobile
>engine, though.)


Direct combination of nitrogen with oxygen is an equilibrium process

N2  + O2 <-----> 2NO

and the equilibrium favors the left side of that equation (damned
little NO formed)

At 2400 degrees Centigrade there will be ~2.2% NO by volume.

At 3200 degrees Centigrade ~4.4%.

Doesn't look like one should expect much NO formed at copper melt
temperatures. AFAIK copper is not a catalyst in the reaction.