On Sun, 3 Nov 2002, John Carmack wrote:
> http://www.armadilloaerospace.com/n.x/Armadillo/Home/News?news_id=180
...We also tried a more aggressive cleaning -
rinsing the screens in 50% nitric acid... ...when
we cleaned the pack, there were some red fumes given off
(red fuming nitric acid?), which we were careful not to
breath. That may have been from the stainless screens,
rather than the silver.
Hmm, interesting. Concentrated nitric acid plus copper is one route for
making NO2:
Cu + 4HNO3 -> Cu(NO3)2 + 2NO2 + 2H2O
The standard references don't mention silver as an alternative to copper,
but given relative costs that's not surprising! My chemistry is too rusty
to decide from first principles whether it's definitely the same reaction
at work, but it seems a reasonable guess; they *are* in the same column of
the periodic table, which tends to mean strong chemical similarity.
In any case, reddish or brownish fumes from any reaction involving nitric
acid have a high probability of being NO2. Which is extremely dangerous;
in particular, it's notorious for causing slightly delayed lung damage.
If you do this particular cleaning procedure again, I would recommend
doing it outside, and watching from upwind. It is hard to be too cautious
with that stuff.
Henry Spencer
[EMAIL PROTECTED]
_______________________________________________
ERPS-list mailing list
[EMAIL PROTECTED]
http://lists.erps.org/mailman/listinfo/erps-list
