On Mon, 28 Feb 2011 09:34:35 -0800 (PST), you wrote:
>Was looking at the MSDS for the 30% h2o2 .. yikes ..
>This etching boards can be dangerous stuff .. lol
It won't be as dangerous as you think. Use 30 VOL (produces 30 times
more oxygen) H202, That's 3% Hydrogen Peroxide. You get it at
drugstores and the like. NOT 30%.
Harvey
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>Randy
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>________________________________
>From: jurod81 <jurod81@...>
>To: Homebrew_PCBs@yahoogroups.com
>Sent: Mon, February 28, 2011 11:03:38 AM
>Subject: [Homebrew_PCBs] Re: Question for the chemistry majors !!
>
>
>Hey Randy-
>I will preface this with - I am not a chemistry major, but I do know a bit of
>chemistry (more organic than inorganic).
>To answer the original question: what the bubbles are that come off of the board
>from peroxide + HCl etch, it is actually brings up an interesting bit of
>chemistry. If you look at a oxidation-reduction table you will see that hydrogen
>is below copper, so as a rule of thumb most Brønsted-Lowry acids such as HCl
>cannot oxidize copper by themselves (nitric acid not included). Peroxides are a
>little special; they are very unhappy molecules and easily decompose into
>hydroxyl radicals on their way to becoming water. These hydroxyl radicals have
>an oxidation potential close to fluorine and can easily attack copper metal
>which has a full outer electron shell. The bottom line is that the gas given off
>on the copper clad is oxygen (O2) and hydrogen (the final electron receptor in
>the reaction), and I am sure that a bit of HCl off gassing since this is an
>exothermic reaction. You end up with copper chloride as a final product. If you
>want to practically speed up the reaction electrolysis is not going to help you
>by very much, I would suggest either starting with a higher % of peroxide,
>agitate your solution (with air bubbles or shaking) or warm you solution up a
>bit.
>
>For those that are interested, Iron choride acts as a Lewis acid since Fe(III)
>has a higher reduction potential then copper with will act as an electron
>acceptor. The iron is reduce to Fe(II) and you end up with copper in solution.
>Ammonium persulfate works on a similar free radical principle as the peroxide +
>HCl principle, the only downsides are that it tends to be slower, you end up
>with ammonia gas given off, and the persulfate decomposes rather quickly after
>you add it to water meaning it is not very reusable (a day or two at the most
>depending on how contaminated your starting water was).
>You can reuse your etchant many times before tossing it (I recharge mine by
>adding a bit more 30% peroxide). When you do toss it you can easily reclaim your
>copper before dumping it down the sink since copper ions do very terrible things
>to the environment (and your septic system's bacteria). You can neutralize the
>acid by throwing some baking soda (Sodium bicarbonate) into the solution and the
>peroxide by dumping some bread yeast which contains an enzyme called peroxidase
>into the solution. You end up with a solution containing copper chloride and
>sodium chloride in solution. Then you can run an electrolytic cell with copper
>as the cathode (hooked up to the (-) terminal) and an inert carbon anode.
>Chlorine will be given off at your anode and your cathode will grow some more
>copper until the solution becomes depleted (then hydrogen bubbles will start
>forming on it). Otherwise you may want to consider disposing of it as hazmat
>when your county does one of those household hazardous material drop-off days.
>My township does one every 6 months or so good for dropping off unused paint
>etc.
>-JRod
>
>BTW - Hydrogen and oxygen are a bad combination. All they need is a little heat
>or a catalyst to get over the activation energy and you have fire.
>
>--- In Homebrew_PCBs@yahoogroups.com, "Randy S." <rj3819@...> wrote:
>>
>> I'm not talking about Chemistry.com here either ..lol
>>
>> Ok .. using muriatic acid .. with the hydrochloric acid in it mixed with
>> peroxide.
>>
>> I looked a chemelec's website where he uses sulfuric acid and electrodes
>> to remove over 90% of the copper, then finishes the board off in ferric
>> chloride.
>>
>> So .. I thought if should work with other acids ..
>> I put a electrode in on the negative lead and a scrape piece of board on the
>> positive lead, started cranking up the voltage .. and it did indeed start
>> drawing
>> current and bubbling .. no ventilation so I shut it off right away ..
>>
>> The questions are :
>> He mentioned gases from the electro-etch process, which makes sense as
>> there are bubbles .. which are toxic .. I assume the gases from his acid would
>> be different then the gases from mine. Chemistry majors ?? What is the gas
>> being released from my H2O2 and HCL LOL
>> Some kind of a hydrogen chloride gas ?? sounds toxic and flammable .. lol
>>
>> I was thinking I would make a setup to use my solution, aearate the tank and
>> use some electro-etching, if that what it is , to help the process along ...
>>
>> Sound ok ? Would there be problems with that ?
>>
>> thanks all
>>
>> Randy - N2CUA
>>
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