@dubob4432
The percentages you give for hydrogen peroxide used to bleach hair are called "volume strength". Volume strength refers to the volume of oxygen evolved from a volume of solution. That is, one mL of 20 (volume strength) will evolve 20 mL of oxygen. That is not the same as wt%, which is the standard way chemists and others measure its concentrations. It is all explained in Wikipedia.
Here is a table showing volume strengths and wt%:
http://www.h2o2.com/technical-library/physical-chemical-properties/physical-properties/default.aspx?pid=13&name=Equivalent-Values-of-ConcentrationJohn
----- Original Message -----
From: dubob4432
To: Homebrew_PCBs@yahoogroups.com
Sent: Saturday, November 17, 2012 8:10 PM
Subject: [Homebrew_PCBs] Re: Kepping Your Etchant Good? Multiple Use? Muriatic Acid / H2O2
since hair dye uses hydrogen peroxide in 10%, 20% and 30% strengths, would this be a better way to go?
reason i ask is because the only freezer i have is a regular freezer/fridge unit and not sure if it would get cool enough?
bob
--- In Homebrew_PCBs@yahoogroups.com, "smilingcat90254" <smilingcat@...> wrote:
>
> You can purify 3% (drugstore grade of H2O2) by placing the H2O2 solution in a dark plastic bottle. No grease or other organic except the plastic and definitely not in a stainless steel or other steel vessel and FREEZE IT IN A DEEP FREEZER. When the solution has formed ice, remove the ice and the remaining liquid is concentrated H2O2. And you can use the concentrated H2O2 into your Acid bath without diluting the concentration of HCl (well not as much as if you had used 3% H2O2).
>
> Word of WARNING!! concentrated H2O2 can be very unstable so do NOT make a big batch! Make only what you need for the acid bath. Do not allow it to come in contact with oil, flesh, stainless steel. Steel act as a catalyst to decompose H2O2 in highly exothermic (heat producing) decomposition of H2O2 into water and oxygen. The reaction can runaway and cause the container to explode from too much pressure build up from oxygen generation. H2O2 does not explode chemically.
>
> Far as storage of acid bath with H2O2. keep it away from sunlight, halogen light or any light with blue and UV in it. Light will promote decomposition of H2O2.
>
> ---- on slightly different subject using vinegar ----
>
> Vinegar is acetic acid. Grocery store vinegar is only about 4% acetic acid. If you want to concentrate and use it for etching copper I think you can do this... To concentrate vinegar you can also freeze the vinegar and remove the ice. It's relatively easy to get 40% concentration of acetic acid if I remember correctly.
>
> Be safe!
> Ms. Smilingcat
>
> Thank you for your note Mitch
>
> --- In Homebrew_PCBs@yahoogroups.com, "dubob4432" <dubob4432@> wrote:
> >
> > I have been using H2O2 from the pharmacy / Muriatic Acid combo, 2:1 - works well and is easy to get, but it doesn't work after the initial use. It seems every etch, I need to make a new batch. The etchant turns into a bright lime green color on the first etch and it does what I need to pretty quick and it seems like there is decent activity - bubbles which only happens on the first time use, after that maybe bubbles when I first put in the pcb/Cu but they go away very quickly.
> >
> > After use, I will put the solution in a clear, sealed glass container and even if I use it the next day, after I start, 45min later my etch is still not done, so I dispose of it and make a new batch at which time I am done in 15mins.
> >
> > What am I doing wrong or where is the mixture out of balance? Again, I just did an etch this evening and had to make a new batch, which is now a bright lime green color.
> >
> > Thanks in advance,
> > Bob
> >
>
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