Aqua Regia Disposal...

Mary Tang mtang at
Mon Oct 29 16:16:03 PDT 2007

Hi all --

I spoke with Kevin -- I think this is covered.


Kevin Crabb wrote:
> Hello SNF Safety Folks,
> I am hoping to use aqua regia (mixture of 3:1 concentrated 
> hydrochloric acid to concentrated nitric acid) to remove platinum and 
> gold grid structures from my wafer. I was told it is okay to do this 
> at the wetbench general, as long as I collect my waste separately.
> However, after doing more research, it has come to my attention that 
> aqua regia will fume (it produces chlorine gas) for hours/days 
> (depending on the temperature, volume), and I was wondering how best 
> to deal with this. Would it be possible to leave the waste container 
> open in the fume hood until it finishes fuming? If not, is there a 
> vented bottle cap that could be used? Any information/suggestions on 
> how to handle this situation would be greatly appreciated. Thanks,
> Kevin
> kcrabb at <mailto:kcrabb at>
> PS—If it matters, I expect to only need ~200mL of the aqua regia mixture.

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at

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