Something for the WIKI or FAQ? PCB etching chemicals

[RLBJR65]

This thread (http://www.diystompboxes.com/smfforum/index.php?topic=50426.msg377092#msg377092) reminded me of a topic I wanted to post a while ago. I thought it would be a good idea to have a list of the most common / safest enchants available. There is a ton of info here already but you have to look everywhere to find it.

My thoughts were that the list should contain any health issues, advantages, disadvantages, any tips like mixing, heating etc.
Also how to properly dispose of the chemicals once they are used up. Anything else?

The 3 most popular seem to be Ferric Chloride, Ammonium PerSulphate and Sodium PerSulphate. Probably others that I never heard of.

I have only used Ferric Chloride so I will start with that. If you have anything to add please feel free.
I know almost nothing about Ammonium Persulphate or Sodium Persulphate. Can someone fill those in?

Ferric Chloride A.K.A. Iron Trichloride, Iron Perchloride
Material Safety Data Sheet (MSDS)
http://www.mgchemicals.com/msds/english/liquid/415-liquid.pdf

Advantages:
Easy to use, sold in premixed form.
Fairly inexpensive and easy to find.
Does a very good job etching.
   .
Disadvantages:
Can cause chemical burns! See MSDS for other health concerns.
Stains almost everything it comes into contact with.
Will corrode other metals.
The chemicals dark reddish color makes it difficult to check etching progress.

Tips:
Works best when warmed. 100 - 120 degrees Fahrenheit or 38 - 49 degrees Celsius is hot enought. Do Not Boil!
Aerating and or agitating also speeds etching.

Disposal: I can't explain it any better than Mark Hammer already has. Thanks Mark!
http://www.diystompboxes.com/smfforum/index.php?topic=50426.msg377103#msg377103

Baking soda (NOT baking powder) will produce a chemical reaction with ferric chloride that will render the solution relatively harmless to the environment.  It is how I have been disposing of my etchant for decades now.

Note the following, though:

Like any rapid chemical reaction, heat is produced so you do NOT want to engage in this on a large and rapid scale; a little bit at a time, wait for it to settle down, and then continue with a bit more
The reaction results in a foam-like substance being produced which dries into something that looks like rust-coloured styrofoam.  The byproducts of the baking-soda/ferric-chloride interaction occupy about 7-10x the volume of the original ingredients.  This means that if you have a tub of etchant, filled to the brim, and you dump a box of baking soda into it, the reaction will overflow the container and cover your counter with ooze within  20 seconds or so.  Keep in mind that the "ooze" is partly de-activated byproduct by also not-yet-deactivated etchant which will stain for life anything it comes into contact with.  So, you will need a large container (or else place small amounts of your main etchant bath in a medium container) to contain the whole mess or else you risk something you will deeply regret.
The thing about the etchant is that it may LOOK completely treated when it isn't.  You may have just a small residual film at the bottom of the container, and when you dump a few tablespoons of soda on it, it starts foaming like crazy.  You will want to keep applying the soda until the rust-coloured mess you have is fairly dry in texture.  Once you have turned it from wet and dangerous into dry and harmless, you can simply pour all those crumbly bits into a garbage bag and set it out with all the other household waste.

Finally, etchant can often be extended for use a bit longer.  If you have a way of safely storing and transferring the stuff to another container, let your bath sit idly for a couple of days (at least) so that all the copper precipitates are sitting like a thick mud at the bottom.  GENTLY pour the still-useful etchant from the top into another container.  Now you can dump your baking soda into the thick stuff to finish using up whatever molecules of ferric chloride are still around.

Ammonium PerSulphate
[url]MSDS http://www.mgchemicals.com/msds/english/solids/410.pdf[url]

Sodium PerSulphate
[url] MSDS http://www.mgchemicals.com/msds/english/solids/4101.pdf[url]

Richard