Homebrew PCBs

So I mixed a solution of Muriatic Acid (1/2 cup) & Hydrogen Peroxide (1
Cup) to etch a board. It worked very well but now I am trying to figure
our how much baking soda it would take to neutralize that solution so it
can be safely disposed of.



thanks

Anthony



[Non-text portions of this message have been removed]

I'm sure some whiz can calculate it exactly, i'm no good with math so
i woud try to add an indicator and gradually add the baking soda.

If you have no indicator at hand i'm told cranberry juice will work.
Also i recently discovered radish juice (from the red outer skin) is a
nice indicator, you can guess when i discovered that...


ST

On Thu, May 21, 2009 at 2:53 AM, perri.anthony <perri.anthony@...> wrote:
>
> So I mixed a solution of Muriatic Acid (1/2 cup) & Hydrogen Peroxide (1
> Cup) to etch a board. It worked very well but now I am trying to figure
> our how much baking soda it would take to neutralize that solution so it
> can be safely disposed of.
>
>
>
> thanks
>
> Anthony
>
>

"perri.anthony" <perri.anthony@...> writes:
> So I mixed a solution of Muriatic Acid (1/2 cup) & Hydrogen Peroxide (1
> Cup) to etch a board. It worked very well but now I am trying to figure
> our how much baking soda it would take to neutralize that solution so it
> can be safely disposed of.

A couple of things...

First, don't!  Keep the solution around and use it for other boards.
Eventually it will turn a dark green and become copper chloride
etchant, which doesn't "expire".  Note that this works if you're going
to do it soon, else the peroxide breaks down and etching takes a lot
longer.  If you leave it as-is for a while and want to re-use it, just
add a little more acid and peroxide to "charge" it again.  Once
there's enough copper in solution, you can recharge (regenerate) it
with an air bubbler, then it's good pretty much forever.

Alternatively, add a bunch of copper to it now just to convert it.  I
think I figured a half pound of copper per liter of HCl - you want the
specific gravity (density) of the solution up to at least 1.2 for CuCl
etchant (for details, see Adam's page at:
http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/)

Second, the copper in solution acts as a pH guide.  It's green/brown
in solution, but once the pH rises above 7 it precipitates out as a
white milky fog.  This assumes you have enough in solution to see the
change, though.

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> "perri.anthony" <perri.anthony@...> writes:
> > So I mixed a solution of Muriatic Acid (1/2 cup) & Hydrogen Peroxide (1
> > Cup) to etch a board. It worked very well but now I am trying to figure
> > our how much baking soda it would take to neutralize that solution so it
> > can be safely disposed of.
> 
> A couple of things...
> 
> First, don't!  Keep the solution around and use it for other boards.
> Eventually it will turn a dark green and become copper chloride
> etchant, which doesn't "expire".  Note that this works if you're going
> to do it soon, else the peroxide breaks down and etching takes a lot
> longer.  If you leave it as-is for a while and want to re-use it, just
> add a little more acid and peroxide to "charge" it again.  Once
> there's enough copper in solution, you can recharge (regenerate) it
> with an air bubbler, then it's good pretty much forever.
> 
> Alternatively, add a bunch of copper to it now just to convert it.  I
> think I figured a half pound of copper per liter of HCl - you want the
> specific gravity (density) of the solution up to at least 1.2 for CuCl
> etchant (for details, see Adam's page at:
> http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/)
> 
> Second, the copper in solution acts as a pH guide.  It's green/brown
> in solution, but once the pH rises above 7 it precipitates out as a
> white milky fog.  This assumes you have enough in solution to see the
> change, though.
>
DJ Thanks for the feedback. If I decide to re-use it in the short term what are the precautions I need to be aware of for storage of the solution? The reason I was planning on neutralizing it was that it was so cheap to buy and readily available that I felt it wasn't worth the risk of storing it. Your thoughts?

Anthony

If you are going to store it, preferably use a sealed glass container. 
Don't leave it in an open container as the fumes can make any nearby 
steel go rusty. Some plastic containers are slightly porous so over time 
acid fumes can escape and rust any nearby steel.

If you want to neutralize it, keep adding sodium bicarbonate (baking 
soda) or sodium carbonate (washing soda) until it stops fizzing. Washing 
soda is probably better because baking soda will fizz a lot so you will 
need to add it slowly. Another trick I have heard of is to mix it with 
cement. That way you end up with a neutralized block.

Les


perri.anthony wrote:

> DJ Thanks for the feedback. If I decide to re-use it in the short term what are the precautions I need to be aware of for storage of the solution? The reason I was planning on neutralizing it was that it was so cheap to buy and readily available that I felt it wasn't worth the risk of storing it. Your thoughts?
> 
> Anthony

Leslie Newell wrote:
> steel go rusty. Some plastic containers are slightly porous so over time 
> acid fumes can escape and rust any nearby steel.

Does anyone know if those black plastic "accordion bottles" used for darkroom 
chemistry fall into this category? The ones I have are made from HDPE, if that 
makes any difference.

> If you want to neutralize it, keep adding sodium bicarbonate (baking 
> soda) or sodium carbonate (washing soda) until it stops fizzing. Washing 
> soda is probably better because baking soda will fizz a lot so you will 
> need to add it slowly. Another trick I have heard of is to mix it with 
> cement. That way you end up with a neutralized block.

Admittedly this was for neutralising FeCl, but I was told that mixing the 
stuff with Plaster of Paris would neutralise it and leave you with a solid 
block that can be thrown away with normal rubbish. Can anyone confirm this?

I've got a 2-litre bottle of extremely diluted and somewhat polluted (with 
etch-resist pen ink, of all things!) FeCl sitting in my cupboard, it's gotten 
to the point where the bottle is lined with brown sludge, the bottle threads 
are covered in green and white crystals (maybe CuCl?), and the solution itself 
is dark brown and useless.

Still, there's another 2ltr bottle with 1.5l of CIF "hyper-activated" FeCl in 
it, which works rather nicely in a bubble etch tank.

-- 
Phil.
ygroups@...
http://www.philpem.me.uk/

Strong HCl will go very slowly through HDPE bottles, leaving some
residue on the outside that looks like a salt and corroding nearby
steel. Also the plastic will get pitted after a number of years.

H2O2 will also damage HDPE bottles, causing them to go hard and
brittle from the inside. You will hear cracking when you press on the
bottle and see a spidererb of cracks on the inside. Again this happens
after many months.

In any event H2O2 will not stay for long mixed with HCl, it will want
to break down into oxygen and water. This creates pressure which MUST
be relieved or the bottle may break.

I use only glass bottles now, because I store those chemicals for years.

ST

On Fri, May 22, 2009 at 7:06 PM, Philip Pemberton <ygroups@...> wrote:

> Does anyone know if those black plastic "accordion bottles" used for darkroom
> chemistry fall into this category? The ones I have are made from HDPE, if that
> makes any difference.
>

Stefan Trethan wrote:

> I use only glass bottles now, because I store those chemicals for years.


Yeah but glass bottles are kind of dangerous because can break easily if
dropped or hit...

Also, I would have an hard time to find a glass bottle with a good, wide
opening to pour in chemicals.

Do you have any suggestion?

bye
as

You can buy expensive lab glass bottles that are glass inside and
plastic outside, so if they break nothing spills.

I'm cheap and just careful.

Regarding your need to put stuff back in, glass bottles for lab use
come in two different varieties, narrow throat and wide throat.

I don't need to pour stuff back in since my etchant lives in the
(covered) etching tank all year round.

ST

On Fri, May 22, 2009 at 8:18 PM, Alessio Sangalli <alesan@...> wrote:
> Stefan Trethan wrote:
>
>> I use only glass bottles now, because I store those chemicals for years.
>
>
> Yeah but glass bottles are kind of dangerous because can break easily if
> dropped or hit...
>
> Also, I would have an hard time to find a glass bottle with a good, wide
> opening to pour in chemicals.
>
> Do you have any suggestion?
>
> bye
> as

Stefan Trethan wrote:

> I don't need to pour stuff back in since my etchant lives in the
> (covered) etching tank all year round.

so this etching tank is the glass container you store your chemicals? Do
you have a photo of it?

bye!
as

I have the etchant in the tank (no photo), and the spare chemicals
(concentrated form) in glass bottles.

The etchant itself does not have a very high concentration of HCl so
it can be kept in the tank which is just closed with a lid (not
airtight).

ST

On Fri, May 22, 2009 at 8:55 PM, Alessio Sangalli <alesan@...> wrote:
> Stefan Trethan wrote:
>
>> I don't need to pour stuff back in since my etchant lives in the
>> (covered) etching tank all year round.
>
> so this etching tank is the glass container you store your chemicals? Do
> you have a photo of it?
>
> bye!
> as
>
>

If you are concerned, put the glass bottle(s) inside another container. 
A suitably sized plastic food storage container would work. I use 
several gallons of fairly concentrated HCl for de-rusting steel and I 
keep it in a plastic tank that is inside another plastic tank. If one 
breaks I have the other. I think the technical term for this is 'bunding'.

Les

> 
> Yeah but glass bottles are kind of dangerous because can break easily if
> dropped or hit...

WalMart sells dilute Hydrogen Peroxide (3%) in brown, recyclable HDPE
bottles.  So, if you replace
it every year or two, I would guess HDPE is a great storage for H2O2.

If I remember right back in high school (think late 1960's, before
HDPE was popular) we used
glass bottles for almost everything, and polyethylene bottles for
basically the same stuff, just
as transient containers (think students handling this stuff in high
school - scary thought)

We only had one injury I heard about that is more than minimal.  One
of the lab techs was in the
store room when the water evaporated down low enough so metallic
phosphorus was exposed to
air.  He was mainly surprised when it exploded (chemically, not an
explosion, just a fast burn
as the phosphorus was exposed to more oxygen in the air) and stuff
came off the shelves in the
store room and hit him. ... minimal injury really, but enough to be
reported.  The metal tin the
phosphorus was stored in was not closed sufficiently (it was like a
paint can) so eventually a
good covering of water evaporated exposing the phosphorus.

sorry about the rambling...

In short, HDPE or PE should be good for storage, just don't consider
it permanent storage.

Hey Jack would you read the email about the PCB file? I would like to
etch it today but I need the right file

bye!
as



Jack Coats wrote:

> WalMart sells dilute Hydrogen Peroxide (3%) in brown, recyclable HDPE
> bottles.  So, if you replace
> it every year or two, I would guess HDPE is a great storage for H2O2.
>

Yes plastic is fine for transit, and to store it some months, but not
several years.

The phosphorus was in some kind of oil, not water, water would ignite it.

ST

On Fri, May 22, 2009 at 10:27 PM, Jack Coats <jack@...> wrote:
> WalMart sells dilute Hydrogen Peroxide (3%) in brown, recyclable HDPE
> bottles.  So, if you replace
> it every year or two, I would guess HDPE is a great storage for H2O2.
>
> If I remember right back in high school (think late 1960's, before
> HDPE was popular) we used
> glass bottles for almost everything, and polyethylene bottles for
> basically the same stuff, just
> as transient containers (think students handling this stuff in high
> school - scary thought)
>
> We only had one injury I heard about that is more than minimal.  One
> of the lab techs was in the
> store room when the water evaporated down low enough so metallic
> phosphorus was exposed to
> air.  He was mainly surprised when it exploded (chemically, not an
> explosion, just a fast burn
> as the phosphorus was exposed to more oxygen in the air) and stuff
> came off the shelves in the
> store room and hit him. ... minimal injury really, but enough to be
> reported.  The metal tin the
> phosphorus was stored in was not closed sufficiently (it was like a
> paint can) so eventually a
> good covering of water evaporated exposing the phosphorus.
>
> sorry about the rambling...
>
> In short, HDPE or PE should be good for storage, just don't consider
> it permanent storage.
>
>

There is white phosphorus that you store in oil, and red phosphorus
that you store in water, or
the other way around. ... Just don't mix them up!  The one you store
in oil can actually grab
the oxygen it needs to oxidize out of the water.

It has been so many years since I played much in a chem lab.  I leave it to
others in case it is needed now!  Still understanding the basics enriches life,
but that can be said for so many fields.

Looking on Wikipedia, it looks like white phosphorus is not soluble in water,
and was used in making napalm (a favorite tool back in the Vietnam war days).
On one chemical supply house site, it says that white phosphorus may be
transported and/or stored in an aqueous bath (under water).  White phosphorus
is used in making flares and agricultural chemicals.

The red phosphorus does not spontaneously combust in air until 240C.
Kind of out of the range of normal environmentals.  It is used to make
matches easy to strike, etc, and is susceptible to ignition my sparks.
To slow its oxidation, it looks like storage in an oil or rare gas is normal.

Reading, it appears there are two more allotropes of phosphorus, violet and
black.  Reading this reminds me why I enjoyed inorganic chemistry.

Enjoy.

IHS ... Jack

On Fri, May 22, 2009 at 11:53 PM, Stefan Trethan <stefan_trethan@...> wrote:
> Yes plastic is fine for transit, and to store it some months, but not
> several years.
>
> The phosphorus was in some kind of oil, not water, water would ignite it.
>
> ST
>