Margaret:

Conceptually, an acid still is a semi-closed version of an
acid etching or passivating bath. The hazard identification
and associated risk management is very similar. Engineering
must be done to resist the acid, liquid or vapor. As Ralph
points out, the mists destroy metal duct work, so
engineering to ensure that all wetted surfaces are
polypropylene with leak-tight seams is critical. Mist
control is frequently done with a water quench of the
mist/air mixture. Engineering to prevent worker inhalation
and skin/eye exposure must be implemented. On dip tanks,
respirators are usually worn, but the semi-closed still and
placing it in a properly constructed hood should reduce that
route of exposure. All electrical systems must be sealed as
the acid mist will destroy copper quickly.

A robust equipment integrity/maintenance/inspection program
is a must.

Monitoring for exposure and occasional fugitive emissions is
essential.

Training and high level (ongoing) supervision of the workers
is necessary.

The electronics industry uses acid etch systems routinely;
they can be operated safely.

Get the MFGs information and customize their recommendations
to your needs. If you want to pursue this further, ping me
offline.

Neal

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-----Original Message-----
From: ACS Division of Chemical Health and Safety
On Behalf Of Stuart, Ralph
Sent: Friday, March 29, 2019 2:33 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: Re: [DCHAS-L] Acid Stills...

> >So these are sub-boiling stills...not sure what
temperature is used (yet) but obviously elevated to some
degree but below boiling. According to the mfg : " High
purity acid vapor is produced, while metallic impurities in
the acid feedstock remain in the liquid phase"...
>
I have had experience with reviewing the condition of
ventilation ductwork after several years of this type of
work has been conducted in two or three labs. The results
were not pretty, to say the least. My experience is that
this is not a standard lab design problem, either for the
lab workers, the building designers or the facility
operators.

I would strongly suggest that you and the faculty member
visit someone who is doing similar work to see what steps
are taken to protect the building from the chemistry and to
see how successful those steps have been. It's not a
situation where general repurposing of standard lab
equipment works well.

Good luck!

- Ralph

Ralph Stuart, CIH, CCHO
Environmental Safety Manager
Keene State College
603 358-2859

ralph.stuart**At_Symbol_Here**keene.edu

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