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Date: Tue, 4 Sep 2007 12:29:39 -0400
Reply-To: "Dr. Jay A. Young" <chemsafety**At_Symbol_Here**VERIZON.NET>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: "Dr. Jay A. Young" <chemsafety**At_Symbol_Here**VERIZON.NET>
Subject: Re: nitric acid mixture with aqueous IPA
Comments: To: al.muehlhausen**At_Symbol_Here**CIBAVISION.COM
Al,
Your concern is well-placed. In many instances, the procedure you describe
would not cause any dire consequences. BUT! There is always the exception
(Murphy's Law) operating in the background. As you know, conc HNO3 is a
pretty d____ good oxidizer and it WILL oxidize any poor,unfortunate reducing
agent in an eager, not to say voracious, manner. When, one day, somebody
uses the procedure described, the reducing agent will acquiesce a bit too
readily and the resulting exotherm could very well be catastrophic.
Jay A. Young
******************************
----- Original Message -----
From:
To:
Sent: Tuesday, September 04, 2007 9:49 AM
Subject: [DCHAS-L] nitric acid mixture with aqueous IPA
Has anyone heard of the practice of mixing concentrated nitric acid (70%)
waste contaminated by small amounts of organic polymer with aqueous
isopropyl alcohol as a means to "passivate" the waste so it can be safely
mixed with aqueous mildly acidic waste streams? One of my scientists
recently described this "passivation" practice as routine during his
experience, but I am sceptical about mixing the oxidizer with a flammable
organic, even if the IPA is in aqueous solution. The procedure does not
seem prudent to me, even under controlled conditions, and I have
recommended against implementation. Here is the written procedure he
provided:
"The procedure for passivation of HNO3 is as follows. 600 ? 800 mL of 50%
(weight) isopropanol in water is prepared in a 1-L beaker. The 50 ? 60 mL
of depleted HNO3 is added slowly to avoid any sudden temperature rise.
This addition is accompanied by an evolution of gas, and the contents of
the beaker change color from a deep orange to a lemon yellow. Upon
completion of the addition, the beaker is stirred or swirled gently to
degas, then capped with a watch glass and allowed to stand and complete
passivating and degassing overnight (at least 12 hours). In the morning,
the mixture is again stirred to remove any traces of gas, and then is
commingled with the normal laboratory waste stream."
What are your thoughts regarding the safety of the proposed procedure,
and do you have recommendations for the best nitric acid waste handling
practices.
Kind regards,
Al Muehlhausen
CIBA Vision Corporation
Chemist/Certified Industrial Hygienist
Health, Safety, and Environmental Officer JCE/JCA/BTI
Office 678-415-4217
Cell 678-644-7026
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