Sheer lunacy.  The "gas" evolved is no doubt toxic NOx, and even if 
the protocol did work safely with added water to buffer the 
temperature rise, the potential that someone will omit water (or use 
ethanol etc.) and have a catastrophic event is quite high.  See:

	http://www.ehs.berkeley.edu/lessonslearned/labslessons3.html
	http://www.ab.ust.hk/sepo/tips/ls/ls005.htm

I witnessed firsthand an accident involving concentrated nitric acid 
and a dry ice/ethanol bath.  There were three injured persons, one of 
whom required skin grafts, as well as a large fire.   Alcohols and 
nitric acid (or any other strong oxidizer) are not compatible, period.

The use of the words "depleted" and "passivate" sound like they come 
from the Bad Chemists Propaganda Ministry.

Rob Toreki

>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

-- 
   =====================================================
Safety Emporium - Lab & Safety Supplies featuring brand names
you know and trust.  Visit us at http://www.SafetyEmporium.com
esales**At_Symbol_Here**safetyemporium.com  or toll-free: (866) 326-5412
Fax: (856) 553-6154, PO Box 1003, Blackwood, NJ 08012

Previous post   |  Top of Page   |   Next post