[meteorite-list] Etching processes and variants : Message from Zelimir Gabelica

From: Pelé Pierre-Marie <pierremariepele_at_meteoritecentral.com>
Date: Sat Dec 25 02:50:24 2004
Message-ID: <20041225075022.37306.qmail_at_web25807.mail.ukl.yahoo.com>

Dear list,

For some reason, Zelimir Gabelica is not able to
transfer you the following message from his Belgian
computer (his 3 attempts, since Dec 22, were
unsuccessful). He is therefore asking me to forward
you its copy, assuming I might have more success with
my computer. I hope hat you could read it safely soon.
Pierre-Marie PELE
------------------------------------------------------

Hello Mark, Adam, J?rn, list,

Thanks to all for your interesting comments about the
etching processes and variants.

Here I wish to add a couple of tips, hoping it can
help.


1) Mark F wrote:

"At WWU we had a once nice Nantan that was showing
signs of rapid corrosion and we got a acrylic
container and filled it with argon for a few
seconds with the top ready to put into place. It had
sealing grommets so would be "air-tight" and we
believe its secure enough to keep the argon in.
Nitrogen is another gas that would work I believe but
am not sure.
Don't know how the mixing of gases to make new
compounds will affect the Nantan over time, but at
least the salty Bellingham, WA air cannot get to it
any longer".

Both nitrogen and argon are inert (non oxidative)
gases but argon has the advantage to be heavier than
air (and thus nitrogen). You can therefore pour it
in a container (from the top, like an invisible
liquid) and, because of its higher density, he will
get at the bottom of tha flask/container and expell
the air (nitrogen) upwards.
At the limit, you can keep argon at the bottom even
without plugging the flask (provided its stays
immobile). But just don't use argon if the aperture
of your container is at the bottom (for obvious
reasons).
On the other hand, physical mixing of nitrogen and air
is tricky because of the quasi same densities of
oxygen (about 20% as admixture in the air) and
nitrogen (80%).

2) Adam wrote:

> After polishing the specimen clean it using 99.9%
pure ethyl alcohol in a hypersonic cleaner. Remove it
from the bath and wipe it immediately with a lint free
cloth. Then slowly heat the specimen to drive off any
remaining liquids. We use an infrared heat lamp with
air circulating around the specimen to drive off
excess moisture. We take the specimen up to 150
degrees Fahrenheit for 40 minutes and then cool it
down slowly. If the alcohol is left to air dry it has
a tendency to attract water so it should always be
heated..."

Here I can add an old tip that chemists use to remove
water from precipitates (powder). We use to wash the
water impregnated solid (powder...) with ethanol
and then wash with di-ethyl ether ("light" liquid easy
to find at any chemist's, though its breathing should
be avoided).
Di-ethyl ether, as totally miscible with ethanol, will
remove its last traces through dissolution (as ethanol
is the major component) and ether can then be
far more easier removed through evaporation, even at
ambient temperature, as it is very volatile.
In short, ethanol removes minor traces of water and
ether then removes traces of ethanol. This avoids
heating the meteoite. Or, if you heat it, you can then
use a lower temperature and heat for a short time).

Best wishes,

Zelimir


        

        
                
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Received on Sat 25 Dec 2004 02:50:22 AM PST