If you have a experience with the process then you can probably
throw away the instrumentation and do it by eye, noise and
conscious. Etching solutions aren't that critical. The ability to
perform titration will give you confidence that the bath is
running at optimum for someone who is inexperienced. The two
variables are free HCl and solution density (which indicates a
copper content).
I found the "cheap" hydrometers that don't comply with any
standard are not worth their money. I've compared them to good
ones and the difference in readings is shameful. The BS718
standard hydrometers are not hugely more expensive, in Australia
$31 compared to $18 "educational" hydrometers.
rolanyang wrote:
> For a etching tank, I used a tupper "juice" pitcher which can be
> purchased from the local grocery store or around here in NJ... the
> 99-cent stores.
>
> I haven't run into problems with an imbalanced etching solution yet,
> but if I did notice sludging that didn't clear up with aeration, I
> imagine one
> could buy a beer/wine hygrometer for cheap
> ( http://brewsupplies.com/cgi-bin/quikstore.cgi has them for $5 a
> piece ).
>
> and if the sludging still didn't clear up after correcting the sp
> density of the water,
> then it can be assumed that the solution may need more HCl.
> At which point I would add a nonscientific "dash" to the bath every
> now and then
> until the sludge cleared up.
>
> All that laboratory equipment seems like a bit of overkill to
> maintain a simple
> bath of CuCl etchant - which doesn't really need a precise PH to
> perform
> its duty.
>
> --- In Homebrew_PCBs@yahoogroups.com, adam Seychell
> <adam_seychell@y...> wrote:
>
>>No reason I can think of. picnic coolers are cheap, and have a good
>
> lid. I built
>
>>my tanks because I needed those dimensions. I coudnl't find
>
> anything off the
>
>>shelf that was narrow and deep enough, base = 45x250mm high = 350
>
> mm.
>
>>Any of the food plastics are ok with strong acids.
>>Now you only concern is getting hold of some lab equipment.
>>
>>Here is lab order list.
>>
>>1 ∗ 5 ml class B volumetric pipette
>>(preferred to graduated pipette)
>>(buy a second in case you break it)
>>1 ∗ rubber bulb pipette sucker
>>1 ∗ 125 ml dropper bottle for indicator (makes life easier)
>>1 ∗ 50 ml glass burette, class B.
>>1 ∗ 0-50°C (or 0-100°C) glass thermometer
>>1 ∗ 250 ml erlenmeyer flask
>>1 ∗ Bromophenol Blue indicator
>> (1 gram will last you ever and a day)
>>
>>
>>You also have to make some kind of stand to hold the burette, I
>
> made something
>
>>out of wood that was a ∗LOT∗ cheaper than buying a dedicated stand.
>
> Fasten the
>
>>burette with rubber bands to a length of wood, and hold that by a
>
> stand from a
>
>>heavy base using a diagonal pole. The area under the burette nozzle
>
> needs to be
>
>>free to place the erlenmeyer flask.
>>
>>The deionized water and sodium hydroxide is available from most
>
> supermarkets.
>
>>You also need some ethanol to make up the bromophenol blue
>
> indicator. Its
>
>>probably better to get the right indicator rather trying to use
>
> turmeric power
>
>>because it will be easier to see the end point of the titration,
>
> which makes the
>
>>job easier to carry out.
>>
>>
>>
>>>Thanks Adam - this is helpful advice. Is there any reason not to
>>
> use a
>
>>>plastic picnic cooler? I believe these are PVC.
>>>
>>>Grant
>>
>
>
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