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     Dear Friedhelm,

     I apologize if my suggestion did not emphasize they safety concerns
     when using closed vessel microwave digestions or any decomposition
     procedure for that matter.  Please start with small samples if you are
     able and you may even want to begin on a hot plate before you transfer
     to microwave digestions.  I did blow a few bombs with one gram samples
     so please start easy.  Your sample matrix and acids certainly command
     respect.

     JB


______________________________ Reply Separator
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Subject: Re: Microwaving very large Samples
Author:  "Klijn; F. (Frits)" <SMTP:[log in to unmask]> at chicago1
Date:    11/15/1999 9:34 AM


Dear Friedhelm,

I would agree with John Bondarowicz that the Prolabo is a nice instrument.
Although I have never worked with it, it offers the possibility of large
samples in open digestion vessels. I even think it can be automated to
change vessels.
Because of the focussing of the microwaves you don't need to put in so much
energy.

But I want to warn again the use of ordinary kitchen machines, especially if

you want to use closed vessels. In the past we had a few explosions with
closed vessels. In one case even the door came off ending in a post two
meters in front of the oven! And this was a laboratory instrument they said.

So if you want to do closed vessel digestions (nothing wrong with that),
make sure you buy a good and safe microwave instrument.

But still, tens of grams with equally large amounts of HF in a microwave? It

gives me the creeps. Did you consider the amount of HF and SiF4 which will
come off. You do need a good ventilation!
I used to digest these amounts in a platinum dish on a hotplate in a well
ventilated cupboard with a water scrubber. This cupboard showed heavy
corrosion after sometime. So think what might happen to your microwave!

Frits Klijn

> -----Original Message-----
> From: Friedhelm vonBlanckenburg [SMTP:[log in to unmask]]
> Sent: 15 November, 1999 15:03
> To:   [log in to unmask]
> Subject:      Microwaving very large Samples
>
> Hi,
>
> Does anybody know of a microwave system that is capable to take very large

> reaction vessels; that is to decompose tens of grams of silicate with
> further tens of grams or more of HF ?
>
> Regards
> Friedhelm v. Blanckenburg
> University of Berne