Re: Microwave "Criticality" Thread --Actual Meltdown Anecdote

["Michael Kay" <makay@teleport.com>]

The use of microwave ovens in analytical chemistry goes back to the early
1970s. We had borosilicate glass made into a manifold to draw the vapors
from above digestion beakers through a drilled hole in the side of the oven
(a stainless steel commercial microwave) into a Mistair Scrubbing System. We
found that digestions went much faster and more completely than on a hot
plate. We used Teflon "Parr Bomb" assemblies for high-temperature
pressurized dissolutions .

Even with nitric/perchloric acids we never had a problem with this system.
The samples were in the milligrams range. I do not have a citation at my
fingertips, but an article describing the equipment and procedures was
published in Analytical Chemistry by A. AbuSamra et al. in the early 70s.

Yes, radiochemistry was being done back then as part of radiochemical
neutron activation analysis of biological samples. Trace elements had to be
separated from the main matrix if they were at levels that could not be seen
with the usual background elements in biological samples (Br and other
longer-lived radionuclides that contributed to a gamma or beta-scatter
background obscuring the signal from ppb levels of Cr in blood serum).
Biological samples were the hardest to digest.



Michael A. Kay, ScD, CHMM
makay@teleport.com
----- Original Message -----
From: Bjorn Cedervall <bcradsafers@hotmail.com>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Sent: Tuesday, January 25, 2000 8:52 PM
Subject: Re: Microwave "Criticality" Thread --Actual Meltdown Anecdote


> >Maybe someone can post the melting point of borosilicate glass, and >what
> >temperature is approximately achieved in a "white" hot object. >This
> >curious and interesting happening shows that even a home  >microwave oven
> >is capable of pumping a surprising amount of energy >into an object like
a
> >carbon mass, and in reaching very high >temperatures
>
> It seems like a well designed microwave oven could be used to do
interesting
> chemistry experiments (this is a seriously meant comment). Never thought
> about that before - in my case it was probably good that we didn't have a
> microwave oven when I was a kid (I did a lot of experiments at home) - I
am
> sure that it would have turned into something bad. :-) Parents with
> chemistry interested kids and a microwave should probably be aware of the
> possibilities...
>
> Bjorn Cedervall  bcradsafers@hotmail.com
> http://www.geocities.com/bjorn_cedervall/
>
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