approval of sodium sulfide solution

Mary Tang mtang at
Wed Oct 13 07:12:23 PDT 2004

Hi Sung-Woo --

In addition, could we get the following information:

1.  Where will you be using this?  I take it that if you are doing an 
electrochemical etch, that this will be done at wbgaas.  There are 
certain limits to the use of wbgaas for this purpose.  Uli Thumser and 
Jim Haydon have worked out a procedure for setting up an electrochemical 
process there (safe electrical hookup, secondary containment, 
notification to other users of the bench, etc.)  Please make sure to 
talk with them.  It would be really, really nice if we could persuade 
you to write up the procedure (or checklist) as part of your SpecMat 
request.  How much (volume?) do you plan to use at each etching session?

2.  Please be more specific about how you plan to dispose of the waste.  
Because it is used for etching Cu, the used etchant cannot be disposed 
of down the AWN drain.  However, because sulfide solutions can generate 
H2S gas in the presence of acids, I'm thinking it's not a good idea that 
the unused etchant is disposed of down  AWN drain either, since it will 
mix with acids (although, granted, everything is diluted.)  I would 
recommend being on the safe side and collecting unused etchant that you 
do not plan for hazardous waste pickup.  I would also suggest that if we 
can avoid storing this in the chemicals passthrough, that would be 
ideal.  (I don't think it would really be "unsafe" but there is the 
possibility of  vapors mixing, if things are not capped tightly.)  And 
although it is inconvenient, mixing up a fresh batch each time you want 
to do an etch might be a good way to avoid the issue of storage (it 
might also help with ensuring a more reproducible etch!)  If you do plan 
to mix the solution outside the lab, please use an acid bench or fume 
hood designed for this purpose -- H2S might be generated and it's not 
good for you.  Also, the crystals can form sulfuric acid on contact with 
moisture (so avoid getting this stuff in your eyes!)  If the MSDS does 
not provide specific handling info, I suggest you check on the internet 
-- sodium sulfide solutions are frequently used on chem labs and photo 
developing, so there are lots of procedures (and precautions!) listed.


John Shott wrote:

> Sung-Woo:
> You need to start by providing us with a MSDS (Mateiral Safety Data 
> Sheet) for the sodium sulfide.
> It is a legal requirement that we maintain current MSDSs of all 
> chemcials used in our laboratory.
> Thanks,
> John

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

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