Muriatic Acid shelf life?

[Michael Allen]

I've been using this stuff to etch my boards the last 2 or 3 years. I havn't made a box in over a year and got out my bottle to etch a board tonight. But it didn't react with the copper and eventually the agitation just started to take the traces off. Does this stuff have a shelf life? I've had my bottle for about 2 years.....

Michael

[amz-fx]

Yes, it has a shelf life...  it gases off the HCl and loses potency over time. Sounds like it was depleted...

regards, Jack

[petemoore]

I've noticed anything I can smell is changing chemical composition.
 You can tell there's a reaction when this stuff's concentrated...I have a bottle been freexing and thawing for more than ten years.
 I figured ]1rst Im lazy] 2nd Ill find a use for this someday...gotta still be good for something...

[brett]

I'm surprised that (1) muriatic acid is very good for etching, and (2) that it's gone off very much.  Muriatic (=hydrochloric) acid reacts only weakly with copper, even in a concentrated (>32%) form.  As long as a tight lid was on it, there's only a limited amount of HCl that could have escaped as gas.  Perhaps there was some decomposition to Cl2.

I'd recommend etchants are based on redox reactions (e.g. ferric chloride).

[Paul Perry (Frostwave)]

hydrogen chloride is EXTREMELY soluble in water, to the extent that it won't completely evaporate out of solution. From memory, even if you boil it, eventually you get a 20% mixture distilling over.
And I agree that I wouldn't expect hydrochloric acid to etch copper. But if you add hydrogen peroxide, you might get some action (havn't tried it myself). WARNING!! might generate chlorine, whihc is very bad for breathing (my old 4th grade teacher was gassed in World War 1, and you could tell...)

[amz-fx]

As long as a tight lid was on it, there's only a limited amount of HCl that could have escaped as gas.

The bottles have vented caps so that pressure cannot build up in them.  

Put a little hydrogen peroxide with it and the reaction with copper is greatly increased...  it will certainly etch boards then, even with a somewhat weakened HCl concentration.

-Jack

[toneman]

As long as a tight lid was on it, there's only a limited amount of HCl that could have escaped as gas.

The bottles have vented caps so that pressure cannot build up in them.  

Put a little hydrogen peroxide with it and the reaction with copper is greatly increased...  it will certainly etch boards then, even with a somewhat weakened HCl concentration.

-Jack

agree with most every post.
My HCL(pool acid) is still good in original plastic bottles.
except, don't think HCL is good etchant for copper pcbs.
i've never actually tried it; always use FeCL3.
(haven't tried HCL w/HydrogenPeroxide--store stuff is *very* weak)
Might give it a try as soon as weather warms up.
i use FeCL3(Ferric Chloride).
I *DO* use HCL to *rejuvinate* the FeCl3.
I usually bubble etch pcbs in a 5gal container.
When i've determined the etching is slowing down,
i usually add 1cup of HCL to 2andhalf gals FeCL3(half a bucket).
I run a bubbler thru it for 24hrs.
Usually, this makes it where i can etch again.
the H2 is bubbled off, so do outdoors.  H2 goes boom!
the CL goes into solution and is available to the copper.
Copper has more *affinity* for the CL than the FE.
This makes the FeCL3 solution much more thicker.
Makes it a little harder for a small pump.
Doesn't affect bubblers.
Use an acquarim bubbler or a couple in parallel.
For air supply, any that is oil-free.
Bubbler is cheap/easy; spray is faster/better/more$$.
tone