Date: Sat, 31 Mar 2007 09:32:16 -0400
Reply-To: ILPI <info**At_Symbol_Here**ILPI.COM>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: ILPI <info**At_Symbol_Here**ILPI.COM>
Subject: Re: Storing Nitric and Hydrochloric Acids
In-Reply-To: <20070330.213723.192.1.chemcon**At_Symbol_Here**>

I have to respectfully disagree with Jay's opinion below.

Aqua regia is technically a 1:3 (or sometimes 1:4 depending on your 
source) ratio of HNO3:HCl.

These solutions are unstable, and liberate NOx, NOCl, and chlorine 
gas. This makes the hazards of the mixed acids significantly greater 
than the sum of the individual hazards.  The increased *hazard* of 
the mixed solution is undeniable.

That said, the *risk* posed by the mixing of the acids is, of course, 
dependent on the quantities involved.  10 mL of each - low risk.  3 
liters of each - run away!

The *risk* assessment must also take into account the probability of 
the two containers being broken at the same time.  Assuming these are 
stored in a cabinet without other incompatibles, then the chances of 
that are generally low.  However, one can not discount the 
possibility of a pressure explosion of another bottle within that 
cabinet.  For example, if someone accidentally introduced an organic 
into the nitric acid bottle, screwed the cap on, and put it away.  Or 
if someone deliberately prepared an aqua regia solution and stored it 
in the acid cabinet:

To summarize, the hazard is significant and the risk *can be* 
relatively low, but not infinitesimally so.  Therefore, it is prudent 
to segregate the two acids.


At 9:23 PM -0400 3/30/07, Jay Young wrote:
>To summarize, I see no significant hazard in the mixture of hydrochloric
>and nitric acids which is greater than the hazards presented by the
>individual unmixed, separate, acids.  In my opinion, there is no good
>reason to separate the two in storage.

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