On 24/03/12 01:46, sheldon_mp_cooper wrote:
> --- In Homebrew_PCBs@yahoogroups.com, Russell Shaw<rjshaw@...> wrote:
>>
>> On 23/03/12 02:07, sheldon_mp_cooper wrote:
>>> --- In Homebrew_PCBs@yahoogroups.com, Russell Shaw<rjshaw@> wrote:
>>>>
>>
>>>> The deep olive colour is when to add HCl and use as a long-term
>>>> etchant.
>>>
>>> But, at that point, highly dangerous chlorine gas WILL be generated from
>>> the reaction, as was warned about in the other link I referred to where
>>> the gent said he'd used the same etchant for four years.
>>
>> Adding a cup of HCl to a litre of spent or unspent ferric chloride will
>> cause absolutely no outgassing whatsoever.
>
> Well, I guess you must be speaking from experience and I haven't done this
> myself, but this gent who has says it will:
>
> http://www.qsl.net/iz7ath/web/02_brew/14_howto/02_clor/index.htm
>
> Excerpt:
>
> "It's necessary to regenerate it;
>
> 1)At first it's necessary to raise the acidity, adding hydrochloridic acid
> HCl (you'll find at shop as muriatic acid, mixed with water.....ask mum);
> make this work in a open place (DANGEROUS GAS) addig HCl until the muddiness
> in the tank disappears (or you can also use a litmus paper)."
I've never had that problem. I'd think it would only happen if the FeCl3 was
undiluted (little if any water), and the HCl was stronger than the watery
hardware shop stuff.
I started with the undiluted FeCl3 diluted with an equal amount of water, and
now just top it up every few months with some hardware shop HCl (which has water
in it).