Mac said:
No, but I wouldn't want to handle fuming nitric acid outside of a properly
equipped lab. Also, you can use fuming nitric acid to make TNT, IIRC. So
maybe people will become interested if they see you buying it. Then again,
it may be so common, and used for so many things that it doesn't register.
Good luck, and be careful.
Mac
Perhaps Jim can send me a lead to the precursors of the encapsulant,
or just ask a chip mfr's process chemist or engineer how they clean up
spills.
If I were working with another experienced chemist, and they told me
they were going to work with fuming nitric acid, I would say "when?"
Commonly available "conc. nitric" is 70%, or about 15M. This is the
stuff in the bottles with the red cap in lab storerooms, and it turns
from water white and clear when new to the yellowish liquid with brown
vapor above it in half filled bottles that you may have seen sometime
in your past.
Conc nitric is hazardous in a lot of ways.
I sometimes use a hot mixture of conc. nitric acid acidified with
sulfuric acid (9 HNO3 : 1 H2SO4) to clean glassware and am comfortable
with my ability to handle that mixture. That mixture is such a
powerful oxidizer that it will oxidize iodide to idoine, which will
form purple vapor and needle crystals in the condenser above reflux,
and can be trapped in the condensate. I dress, pay attention, and
make sure a colleague knows what I am doing, change clothes, shower.
Carelessness with conc. nitric can be dangerous, and an interesting
page may be found at
http://www.ilpi.com/safety/explosion.html
However,
Fuming nitric is an uglier beast. It is sometimes called 90% nitric.
It is poison. Its vapors are poison. Its decomposition products are
poison. It is dryer than distilled nitric acid. It is hazardous to
add water to it. It is energetic. I have never needed to work with
it.
It is hypergolic with many materials. I have heard rumors that
ordinary old flesh, wet red meat, will spontaineously catch fire on
exposure to it. One page that mentions several combinations of
hypergolic partners is
http://www.permanent.com/t-mikesc.htm, though I
don't know how exotically dry their "nitric acid" is. (Chemically,
really, really dry nitric acid would be the nitrogen tetroxide of
rocketry usage on the same page. Nitric acid dried by fractional
distillation is the 70% conc. nitric azeotrope.)
Usually, I think the MSDSes are written by attorneys to cover the
corporations liability, and I make my students read the MSDS for water
and benzaldehyde (the flavor of Maraschino cherries) to keep things in
perspective. Many of the phrases in the MSDS of chemicals that
chemists regard as routine and easy to use are presented in
essentially the same way in the MSDS for fuming nitric. I teach in
lab that this leveling of the report of hazard is an insideous danger
that robs the readers of judgement. I am usually trying to move them
away from a phobia of chemicals.
I am not trying to make you comfortable ragarding fuming nitric acid.
An MSDS for fuming nitric is online at
http://www.sefsc.noaa.gov/HTMLdocs/NitricAcidFuming90.htm
to quote selections:
"
Incompatibilities:
A dangerously powerful oxidizing agent, fuming nitric acid is
incompatible with most substances
"
"Incompatible with" in this context means, in part, "may be hypergolic
at temperature, pressure, and concentration conditions found on the
bench."
