Homebrew_PCBs

That's good you found a place selling that stuff, sometimes these
plastics are hard to locate. Stay with PVC , because its the only
plastic you can easily glue and bend with a hot air.

I've built several air spargers systems over years for aerating
tanks. The 1 mm diameter holes in PVC ridged pipe works ok if you
got a big air supply. It gives you large bubbles and they can
tend to flow into a stream on one side of the tank. Its more
effective to have lots of fine bubbles, as the liquid/air surface
area is increased and tends to produce more uniform sparging. I
use some porous garden irrigation hose. Its usually available in
say 20 meter rolls with a 12 mm ID. The remaining 19.5 meters can
be used on a garden :).

DIY irrigation supplies also make good places to buy chemical
resistant plumbing. Be careful, some fittings are made from nylon
and won't last in HCl. Burn a small part of the plastic and it if
bubbles and fizzles and the smoke is very irritating then its
nylon. If the plastic simply melts when burning and maybe even
drips on the ground then you have polypropylene fittings.
Polyethylene burns similar to polypropylene except the smoke
smells like candle wax smoke.

The more air the better, so buy the largest aquarium air pump you
can afford. I though of using a sewerage treatment aeration
pump, but they are $$$.

grantfair2001 wrote:

> I spent several hours looking for an inexpensive source of schedule 80
> 1/4" PVC pipe and fittings to make the air "sparger" outlined on the
> "Think and Tinker" website.
>
> I was pleasantly surprised with my experience with this website:
>
> http://www.usplastic.com
>
> They sold me 10 feet of 1/4" schedule 80 pipe, two end caps, two 90
> degree elbows and one tee, for $11.97. There was no shipping fee. This
> is much cheaper than several other sources I found on the 'net.
>
> I thought this might be on interest to list members wanting to use
> cupric chloride etchant. (Other than being a happy customer I have no
> connection with US Plastics.)
>
> Grant
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> To unsubscribe from this group, send an email to:
> Homebrew_PCBs-unsubscribe@yahoogroups.com
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>

Thanks for the additional information. Did you use the pipe layout
which Think and Tinker recommends, like a U shape, with the PCB in the
middle between the "legs" (if that makes any sense at all)?

The air tubing I have on hand is Tygon F-4040 A. I know little about
it except it's cheap at my local surplus store and I believe it is
fairly non-reactive to most chemicals. (Please correct me if I am wrong.)

For air I thought I would try a portable tire inflator from Harbor
Freight, or perhaps an old Gast vacuum pump I've had kicking around
for years, if I can figure out how to use it as a compressor. Failing
that a buddy has offered an aquarium pump but my etch tank is a 34
quart capacity Coleman chest cooler, so I am unsure it will have the
needed air volume.

I have also found some cheap 1/2 mL pipettes (C$ .25) and a surplus
100 ml cylinder specified to +/- 1 ml (C$ 7), which seems like it
would be fine for measuring for titration, since the article suggests
results within +/- 10% are fine for adjusting the acid level. I am
hoping a student burette will do the trick since, so far the best
proice for a legit version will set me back $140 Can.

Also- anyone know of a reasonably priced source of bromophenol blue?
So far the best I have seen is C$ 65.00 for 5 grams of ACS grade. That
seems like an awful high price, and if a lab grade is available I
assume that would work ok.

Grant

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell
<adam_seychell@y...> wrote:

> That's good you found a place selling that stuff, sometimes these
> plastics are hard to locate. Stay with PVC , because its the only
> plastic you can easily glue and bend with a hot air.
>
> I've built several air spargers systems over years for aerating
> tanks. The 1 mm diameter holes in PVC ridged pipe works ok if you
> got a big air supply. It gives you large bubbles and they can
> tend to flow into a stream on one side of the tank. Its more
> effective to have lots of fine bubbles, as the liquid/air surface
> area is increased and tends to produce more uniform sparging. I
> use some porous garden irrigation hose. Its usually available in
> say 20 meter rolls with a 12 mm ID. The remaining 19.5 meters can
> be used on a garden :).
>
> DIY irrigation supplies also make good places to buy chemical
> resistant plumbing. Be careful, some fittings are made from nylon
> and won't last in HCl. Burn a small part of the plastic and it if
> bubbles and fizzles and the smoke is very irritating then its
> nylon. If the plastic simply melts when burning and maybe even
> drips on the ground then you have polypropylene fittings.
> Polyethylene burns similar to polypropylene except the smoke
> smells like candle wax smoke.
>
> The more air the better, so buy the largest aquarium air pump you
> can afford. I though of using a sewerage treatment aeration
> pump, but they are $$$.

A bit of research showed that this tubing is definitely not what I
need in an acid environment:

http://www.omega.com/pdf/tubing/technical_section/chemical_chart_1.asp

What would list members recommend? Ordinary aquarium tubing?

Grant

--- In Homebrew_PCBs@yahoogroups.com, "grantfair2001"
<grant.fair@s...> wrote:

> The air tubing I have on hand is Tygon F-4040 A. I know little about
> it except it's cheap at my local surplus store and I believe it is
> fairly non-reactive to most chemicals. (Please correct me if I am

wrong.)

From: grantfair2001
For air I thought I would try a portable tire inflator from Harbor
Freight, or perhaps an old Gast vacuum pump I've had kicking around
for years, if I can figure out how to use it as a compressor. Failing
that a buddy has offered an aquarium pump but my etch tank is a 34
quart capacity Coleman chest cooler, so I am unsure it will have the
needed air volume.
I believe shop compressors create some oil mist... You might want to try bubbling through plain water to test your compressor, before you foul up your etching solution with oil.

Cheers,
- Jan



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

grantfair2001 wrote:

> Thanks for the additional information. Did you use the pipe layout
> which Think and Tinker recommends, like a U shape, with the PCB in the
> middle between the "legs" (if that makes any sense at all)?

Something like that. but I think the porous hose works better.
Aquarium air stones are good too.

>
> The air tubing I have on hand is Tygon F-4040 A. I know little about
> it except it's cheap at my local surplus store and I believe it is
> fairly non-reactive to most chemicals. (Please correct me if I am wrong.)
>

From the chemical chart, Tygon seems ok in most acids. I know
that solid nylon just crumbles apart after a week in 20%(w/w)
sulfuric acid. The only problem with the soft clear PVC tubing is
it tends to become tacky on the surface after a few weeks. It
doesn't seem to penetrate very far.

> For air I thought I would try a portable tire inflator from Harbor
> Freight, or perhaps an old Gast vacuum pump I've had kicking around
> for years, if I can figure out how to use it as a compressor. Failing
> that a buddy has offered an aquarium pump but my etch tank is a 34
> quart capacity Coleman chest cooler, so I am unsure it will have the
> needed air volume.

Try it and see. sewerage treatment aeration pumps are perfect for
the job. I should look on the secondhand market. Last time I
checked a new Nitto Kohki 80L/min pump was about $500.
A 'large' aquarium pump might be 2L/min

>
> I have also found some cheap 1/2 mL pipettes (C$ .25) and a surplus
> 100 ml cylinder specified to +/- 1 ml (C$ 7), which seems like it
> would be fine for measuring for titration, since the article suggests
> results within +/- 10% are fine for adjusting the acid level. I am
> hoping a student burette will do the trick since, so far the best
> proice for a legit version will set me back $140 Can.
>

CA$140 sounds expensive. Here in Australia a lab place near me
sells "Brand" 50ml (class B) burettes for AU$70. Still, expensive
so you might want to have a better look around. Pipettes are not
terribly expensive, around AU$4 to $6. Order as many free
catalogs as you can.

> Also- anyone know of a reasonably priced source of bromophenol blue?
> So far the best I have seen is C$ 65.00 for 5 grams of ACS grade. That
> seems like an awful high price, and if a lab grade is available I
> assume that would work ok.

Yep, that sounds about right. I think the best thing for you to
do is post that question on sci.chem news group explaining you
are titrating HCl in cupric chloride. approx. strengths 1 Molar
and can accept few percent error. I am using methyl orange with
good success.

Thanks for the additional info, Adam. What kind of methyl orange are
you using - aqueous? What percent, 0.1% or....?

(MO seems to be more readily available than bromophenyl blue and not
too pricey). What is the shelf life of the stuff?

I haven't figured out how to access usenet groups with my current
setup, so MO seems the easiest way to go.

Grant

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell
<adam_seychell@y...> wrote: [snip]

> Yep, that sounds about right. I think the best thing for you to
> do is post that question on sci.chem news group explaining you
> are titrating HCl in cupric chloride. approx. strengths 1 Molar
> and can accept few percent error. I am using methyl orange with
> good success.

grantfair2001 wrote:

> Thanks for the additional info, Adam. What kind of methyl orange are
> you using - aqueous? What percent, 0.1% or....?
>
> (MO seems to be more readily available than bromophenyl blue and not
> too pricey). What is the shelf life of the stuff?
>

don't know about shelf life, its from my chemistry set that I got
when I was a kid (~ 20 years ago) and its works fine.
The indicator solution I use is about 0.1% I think. Not
important, just enough to look nice and colorful.
As far as I know, the different indicators are used depending on
pH you want them to change at. For HCl and NaOH titration I think
almost any can be used because the pH change near the end point
is very dramatic as it passes neutral. Its because NaOH is a
strong base and HCl is a strong acid, which means they ionize
completely in water which means there is no free NaOH or HCl
molecules in the solution instead they exist almost entirly of as
ions, Na+, OH- or H+ and Cl-.


In aquious solutions the concentrations (in moles per liter) of
H+ and OH- ions are always at equilibrium according to

[H+] * [OH-] = 10E-14

where [H+] is concentration of H+ ions in moles per liter.
[OH-] is concentration of OH- ions in moles per liter.

so if you add H+ ions to water then there automatically has to be
less OH- ions for the above equation to balance.

now pH is defined as -log10 ([H+])

in pure water [H+] must equal [OH-] and so
[H+] = [OH-] = 10E-7
pH of pure water then is equal to -log10(10E-7) = 7

[H+] of 10E-7 is a small number so if you add tiny bit of HCl to
pure water then [H+] goes sky high and so pH drops down a lot.
The same goes for NaOH and water ,except [OH-] goes sky high
which means [H+] must get a lot smaller than 10E-7 to keep the
equation balanced. Hope this makes some sense.

here is some stuff on indicators

http://ecommerce.hach.com/stores/hach/pdfs/wah/eng_pdf/ex_pHindicators.pdf

Notice in figure 1 showing the dramatic pH change



If you really interested then I'd recommend getting hold of a
secondhand copy of a good 1st year chemistry book and learn about
solution equilibrium.

Adam

> I haven't figured out how to access usenet groups with my current
> setup, so MO seems the easiest way to go.
>

use http://groups.google.com
as a web based NNTP browser and for posting.

i want info about oscillators and their functioning.if anyone has the material pls send it

tnx





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

This would be on topic for lists such as Electronics_101 and
Advanced_Electronics.

http://groups.yahoo.com/group/Electronics_101

http://groups.yahoo.com/group/Advanced_Electronics

Steve, the moderator

--- bhaskaran chidambaram <bhaskaran_india@...> wrote:

>
> i want info about oscillators and their functioning.if anyone has
> the material pls send it
>
> tnx

=====
Steve Greenfield // Digital photography, scanning,
Polymorph Digital Photography // retouching, and photomorphing
253/318-2473 voice // to your specs.
polymorph@... //
http://www.polyphoto.com/ // Based in Tacoma, WA, USA

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