Margaret,

Here is the information I gathered. Note though, that I do not have  
personal experience with soil digestions.

The engineer I spoke with said that at a universities, the duct work is  
most likely carbon steel, galvanized steel or stainless. A quick test is to  
get a decent magnet and test if it sticks. If it sticks, its not stainless  
and you should not do the procedure. If it doesn't stick then you've  
narrowed it down to stainless steel, aluminum or fiberglass. If you don't  
have the experience to tell the difference between aluminum and stainless  
steel then wait for verification from building maintenance coridinator.  
Also note: the engineer warned a common building mistake is for them to  
install stainless steel ductwork, but use a cheapo exhaust fan with  
aluminum blades, you may want to verify that too.

Additional link: The CSB Guidelines for fume hoods (pg 10 indicates it  
should be stainless steel, but might be galvanized)
http://www.ehs.ucsb.edu/units/labsfty/labrsc/chemistry/fhguide_07.pdf

The link below is the EPA approved procedure for hot plate assisted aqua  
regia sample digestion. Note specifically procedure section 11.1.2, as it  
pertains to covering beaker and the suggested temp of 85C while uncovered,  
95C when covered.

-Procedure 11.1.5 is an under emphasized step in my opinion. As the msds  
points that its to avoid an explosion hazard.

Lastly, I myself am curious & worried about a strong reaction. Note the  
MSDS below reactivity profile with metals and hydrocarbons. I recommend  
following the EPAs guidelines of smaller reactant volumes (25ml is more  
than I would want to try this experiment with)

http://water.epa.gov/scitech/swguidance/methods/bioindicators/upload/2007_07_10_methods_method_200_2.pdf

This link (below) is the msds for aqua regia (HCL + HNO3) CAS

http://www.docstoc.com/docs/26426711/SAFETY-DATA-SHEET-AQUA-REGIA

Regards,
Craig
BS Molecular Biology


On Nov 2, 2010 5:05pm, Margaret Rakas  wrote:

> Good afternoon,

> I have a researcher who wants to perform acid digestions involving about  
> 20 mLs of concentrated hydrochloric acid and 5 mLs of concentrated nitric  
> acid which are mixed with her soil, then slowly heated to 95C until most  
> of the acid has evaporated. The methodology, developed by outside  
> researchers, is outlined in a journal article which makes no mention of  
> the use of scrubbers, special fume hood lining, etc.

> The researcher will be wearing a face shield, rubber apron, goggles, lab  
> coat and thick nitrile gloves, with tape around the glove/labcoat  
> interface. I think we have the PPE down pat.

> The process is planned to be carried out in a fume hood, using an open  
> vessel on a hot plate. My concerns is whether we should be using some  
> sort of capture system or scrubber for the acid that is evaporated. I am  
> trying to find out what the ductwork for the fumehood is made of, but it  
> is not a stainless steel hood and I am betting the ductwork is not,  
> either. The researcher is planning on doing somewhere between 20-100  
> samples, depending on how things go, so roughly 400 mLs to 2000 mLs of  
> concentrated acid may be sent through the ductwork...


> I found one review article on acid digestions that stated "...acid  
> digestion must be conducted in a fume cupboard with efficient scrubbers  
> installed..' [Matusiewicz] but no reference to actually how this is done.

> Any suggestions, citations, etc. would be most helpful..

> thanks to all,

> Margaret








Margaret,

Here is the information I gathered. Note though, that 
I do not have personal experience with soil digestions.

The engi
neer I spoke with said that at a universities, the duct work is most likely
 carbon steel, galvanized steel or stainless. A quick test is to get a dece
nt magnet and test if it sticks. If it sticks, its not stainless and you sh
ould not do the procedure. If it doesn't stick then you've narrowed
 it down to stainless steel, aluminum or fiberglass. If you don't have 
the experience to tell the difference between aluminum and stainless steel 
then wait for verification from building maintenance coridinator. Also note
: the engineer warned a common building mistake is for them to install stai
nless steel ductwork, but use a cheapo exhaust fan with aluminum blades, yo
u may want to verify that too. 

Additional link: The CSB Guideli
nes for fume hoods (pg 10 indicates it should be stainless steel, but might
 be galvanized) 
http://www.ehs.ucsb.edu/units/labsfty/labrsc/chemistr
y/fhguide_07.pdf

The link below is the EPA approved procedure fo
r hot plate assisted aqua regia sample digestion. Note specifically procedu
re section 11.1.2, as it pertains to covering beaker and the suggested temp
 of 85C while uncovered, 95C when covered. 

-Procedure 11.1.5 is
 an under emphasized step in my opinion. As the msds points that its to avo
id an explosion hazard. 

Lastly, I myself am curious & worried a
bout a strong reaction. Note the MSDS below reactivity profile with metals 
and hydrocarbons. I recommend following the EPAs guidelines of smaller reac
tant volumes (25ml is more than I would want to try this experiment with)
http://water.epa.gov/scitech/swguidance/methods/bioindicators/upl
oad/2007_07_10_methods_method_200_2.pdf

This link (below) is the
 msds for aqua regia (HCL + HNO3) CAS 

http://www.docstoc.com/do
cs/26426711/SAFETY-DATA-SHEET-AQUA-REGIA


Regards,
Cra
ig
B.S. Molecular Biology



On Nov 2, 2010 5:05pm
, Margaret Rakas <mrakas**At_Symbol_Here**smith.edu> wrote:
>   
  

>       Good afternoon,    
>     

>       I have 
a researcher who wants to perform acid digestions involving about 20 mLs of
 concentrated hydrochloric acid and 5 mLs of concentrated nitric acid which
 are mixed with her soil, then slowly heated to 95C until most of the acid 
has evaporated. =A0=A0The methodology, developed by outside researchers, is
 outlined in a journal article which makes no mention of the use of scrubbe
rs, special fume hood lining, etc.    
>     
    
>  
     The researcher will be wearing a face shield, rubber apron, goggles, l
ab coat and thick nitrile gloves, with tape around the glove/labcoat interf
ace. =A0I think we have the PPE down pat. =A0    
   
>     >       The process is planned to be carried out in a fume hood, usi
ng an open vessel on a hot plate. =A0My concerns is whether we should be us
ing some sort of capture system or scrubber for the acid that is evaporated
. =A0I am trying to find out what the ductwork for the fumehood is made of,
 but it is not a stainless steel hood and I am betting the ductwork is not,
 either. =A0The researcher is planning on doing somewhere between 20-100 sa
mples, depending on how things go, so roughly 400 mLs to 2000 mLs of concen
trated acid may be sent through the ductwork...    
>     
   
     
>     
>       I found one review article on acid dig
estions that stated "...acid digestion must be conducted in a fume cup
board with efficient scrubbers installed..' [Matusiewicz] but no refere
nce to actually how this is done. =A0    
    
>       Any sug
gestions, citations, etc. would be most helpful..    
>     
&
gt;       thanks to all,    
>     
>       Margaret    
>     
>       
> 
>     
>   
&
gt;