Date: Mon, 30 Nov 2009 09:36:29 -0600
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: "Tsiakals, Nicholas John" <tsiakals**At_Symbol_Here**ILLINOIS.EDU>
Subject: Re: HF digestion safety
In-Reply-To: <8E5C750D-2C78-4CFC-9D6C-90D7FC1D6FC2**At_Symbol_Here**>

Can't say I have design experience on local exhaust, but I'll bet the basic
 scrubbing concept is very similar to the first aid concept:  bind the diss
ociated fluorine ion with a group II cation.  (In plainspeak, bring HF in c
ontact with calcium salts or magnesium salts, and you end up with a very st
able fluoride.)  But choose your group II salt carefully!  We have a Honeyw
ell document that indicates Calcium Carbonate as a good selection - slow re
action (meaning exotherm problems are reduced, slow gas evolution).  The sa
me document warns that limestone pebbles can become passivated (coated in r
eaction product which inhibits further reaction).  So either look to use in
creased surface area (small particle sizes) or overbudget for limestone peb
bles.  Perhaps someone else can give higher confidence guidance on this...

Hope this helps!

-----Original Message-----
From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**LIST.UVM.EDU] On Behalf Of Jo
seph Passante
Sent: Monday, November 30, 2009 8:41 AM
To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
Subject: [DCHAS-L] HF digestion safety

Does anyone on this list have experience with proper exhaust design  
for small scale digestion using 48% HF?  The geochemistry researcher I  
am working with anticipates evaporating 2 liters of concentrated HF  
per month in a fume hood.

I am interested in scrubbing technologies and if anyone has designed  
local exhaust systems that do not involve a fume hood.



Joseph R. Passante, CIH, CHO
Associate Director
Chemical Hygiene Officer
Environmental Health & Radiation Safety
University of Pennsylvania

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