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This one seems to cause some very negative comments.



 
 
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  #21  
Old January 23rd 05, 07:06 PM
Morten
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"Morten" wrote in message
...

"spiral_72" wrote in message
oups.com...
Alright, I've got this idea. Boy, that sounds like the beginning to an
end.


The chemical reaction is:

NaHCO3(aq) + HCl(aq) = CO2(g) + H20(aq) + NaCL(aq) + energy


I've done a few calculations and 100g of baking powder together with 0.1447
litre of 30%HCl should give 52.39g CO2 which at room temperature / pressure
should be arround 26.65 Litre of CO2 gas which in turn should be about 2540
bubbles (based on a bubble size of 0.0952ml)

I also did some calculation on the yeast / sugar method and found that 200g
sugar gave about 48.86g CO2 or 24.87 Litre CO2 at room temperature, which is
about 2368 bubbles given the same bubble size as above...

So say that we use a standard Yeast / Sugar batch of ca. 200g sugar that
gives ca. 4700 bubbles over ca. 2 weeks. The Baking powder / Acid mix will
give approximately the same, but because the reaction is self regulating we
can make much bigger batches, ie. we could use 500g of baking powder and
0.723Litre of 30% HCl that would give 12700 Bibbles, lasting 37 days instead
of 14 days for a batch...


And of course the Baking powder / acid method can be shut off and run slow
or fast depending on need, where the yeast / sugar method cannot be
controlled easily with out venting / loosing the CO2 when not needed or
cleaning up the mess after a little mishap...


I still thinks this is a great idea, just haven't had a chance to implement
it yet.

Hmm, I wonder if B&Q are open now...



/Morten





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  #22  
Old January 23rd 05, 08:12 PM
Dan White
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"Morten" wrote in message
...

I've done a few calculations and 100g of baking powder together with

0.1447
litre of 30%HCl should give 52.39g CO2 which at room temperature /

pressure
should be arround 26.65 Litre of CO2 gas which in turn should be about

2540
bubbles (based on a bubble size of 0.0952ml)

I also did some calculation on the yeast / sugar method and found that

200g
sugar gave about 48.86g CO2 or 24.87 Litre CO2 at room temperature, which

is
about 2368 bubbles given the same bubble size as above...

So say that we use a standard Yeast / Sugar batch of ca. 200g sugar that
gives ca. 4700 bubbles over ca. 2 weeks.


It is an interesting idea, but I'm not sure if something sounds right or
not. I'm not a CO2 expert...I don't even use it, but I think I recall
people talking in terms of several bubbles per second. Even if we talk
about 1 bubble/sec over say 12 hours/day for 14 days that makes over 600,000
bubbles! Your bubble at .0952 ml has about a .28 cm radius, so it is a big
bubble.

I don't know how big the 600,000 bubbles are at the 1 bubble/sec rate, but
if we look at your calculation of 4700 bubbles through the yeast method over
that same 14 days, this would say that your bubbles would have to be
600K/4.7K = 128 times the volume of the yeast bubble. So what does that
make the radius of the 600,000 bubbles? .0952ml/128 = .00074 ml, or a
bubble radius of .056 cm or a diameter of 1 mm.

So for people who use yeast, if you get 1 bubble per second, these bubbles
would have to be 1 mm in diameter in order for the "charge" of yeast to last
14 days at 12 hours per day if Morten's 4700 bubble calculation is correct.
Does this make sense?

Just curious,
dwhite


  #23  
Old January 23rd 05, 09:04 PM
Morten
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"Dan White" wrote in message
...
It is an interesting idea, but I'm not sure if something sounds right or
not. I'm not a CO2 expert...I don't even use it, but I think I recall
people talking in terms of several bubbles per second. Even if we talk
about 1 bubble/sec over say 12 hours/day for 14 days that makes over

600,000
bubbles! Your bubble at .0952 ml has about a .28 cm radius, so it is a

big
bubble.

I don't know how big the 600,000 bubbles are at the 1 bubble/sec rate, but
if we look at your calculation of 4700 bubbles through the yeast method

over
that same 14 days, this would say that your bubbles would have to be
600K/4.7K = 128 times the volume of the yeast bubble. So what does that
make the radius of the 600,000 bubbles? .0952ml/128 = .00074 ml, or a
bubble radius of .056 cm or a diameter of 1 mm.

So for people who use yeast, if you get 1 bubble per second, these bubbles
would have to be 1 mm in diameter in order for the "charge" of yeast to

last
14 days at 12 hours per day if Morten's 4700 bubble calculation is

correct.
Does this make sense?


To be totally honest the 0.0952ml per bubble was something i got from a
couple of postings a couple of years back, ie they came from a '1050 bubbles
per 100ml' statement, but your'e right it sounds like a quite a large bubble
:-) and is probably way above a real bubble, anyone done some counting on a
known volume?


/Morten




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  #24  
Old January 23rd 05, 11:39 PM
Elaine T
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Morten wrote:
"spiral_72" wrote in message
oups.com...

Alright, I've got this idea. Boy, that sounds like the beginning to an
end.

I figure I can drop dry ice in a tank, cap it with a regulator and have
CO2 for some period of time for my planted aquarium. Obviously it will
require more than a handful of dry ice and chances are it ain't quite
that simple. Right now I am building a tank with a mouth wide enough to
accept an entire piece. I figger I'll pack the stuff in there like the
old shotgun wadding with a length of 2x2 or something until it's full,
and cap it.

I run a search on this over the web and the Google groups. I got the
same response: "DON'T DO IT, IT'S TOO COMPLICATED"

What's up with dat? Any particular reason? I don't want to hear that
the stuff is not sanitary either. The air in my house probly ain't
sanitary after a nice homemade bowl of chille. Heck, it's free......
They pack ice cream in it at(they sell ice crea the gas station m in
cones) and they just throw it away.




I can see what you're trying to do and I can see the fun in trying it, but
unless you're very good with a tig welder I wouldn't try that at all, I
really dont fancy my liver being spread over to large an area, it's just
fine where it is now.


If the goal of this exercise is to supply a steady stream of CO2 which can
be easily regulated / shut off, why don't you use a setup using baking soda
(NaHCO3) and a suitable acid like HCL or vinegar if you're a pussy :-)


I can't remember where I saw this but a setup with a couple of containers,
one with the acid in a ballon in a slightly presurized container, say 0.1bar
(1m water column), with a hose comming from the ballon to the next container
that contains the bakingpowder with about 2-3 cm of water on top (it wont
all disolve right away but will when the concetration goes down after time)
and another hose comming out to you tank, bubler, regulator whatever...

The theory is that when you add the acid to the saturated bakingpowder
solution the reaction releases CO2 which increases the pressure thus
preventing more acid to flow into the mixing container. When some of the CO2
is used the pressure will drop, allowing some acid to drip into the main
reactor, reacting with some baking powder thus creating some more CO2 until
the pressure reaches a equilibrium at arround the 0.1 bar mark...

The potential yield of this would be quite large, ie. pretty much governed
bu how fast you can supply the acid and how fast the CO2 gas can be used. On
the other hand you should be able to stop using any CO2 at all and the
reaction should stop itselfe because the pressure gets to high for any more
acid to flow into the main reactor and nothing more happens.

It would probably be a good idea to include a oneway valve in the hose
comming from the acid container and oanother in the hose comming from the
main reactor and a couple of stop valves would probably be called for as
well....


The chemical reaction is:

NaHCO3(aq) + HCl(aq) = CO2(g) + H20(aq) + NaCL(aq) + energy


I haven't build this one yet, but where I live baking powder is dirt cheap
and so is the HCl, one could use other acids if no HCl is available.

I would think that standard PVC drain fittings could be used, the pressure
is well within reach of standard schedule40 pipes and fittings, but one
could use schedule80 if paranoid. the hoses could be solicone of standard
vinyl hoses, as long as they're monitored close they should be fine...


What do you think, Is this approach even more insane than the Dry Ice in
container method, as far as I can see it should work just fine, just haven't
hade the time to source some materials yet...


HCl fumes badly in concentrated form, and I think I remember some fumes
from dilute HCl (haven't handled the stuff in a while). Same with
acetic acid for that matter. Wouldn't you tend to acidify the fishtank
some with acid fumes, or are they not concentrated enough to matter?

--
__ Elaine T __
__' http://eethomp.com/fish.html '__

  #25  
Old January 24th 05, 02:36 PM
spiral_72
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An update:

I welded the bottom plug into the tank Friday when I got home. Actually
I am quite pleased with the results. The penetration wasn't quite as
good as I would have liked to see (Man, that's some thick stuff!) but,
1200psi should be no sweat.

Saturday: made a trip to the hardware store.... I bought steel fittings
for the tank to the regulator, regulator to the hose.... I don't have a
needle valve yet..... This should be sufficient for now........... Oh,
and I bought a manual operated valve to blow off tank pressure. The
blow-off valve will be seperate from the regulator........ I bought a
big pipe cap.

I didn't have a drill and tap big enough for the pipe tap at home so
it'll have to wait untill I can di it at work. The cap is about 1 1/2 -
18 thread...... This is big but still much smaller than a chunk of dry
ice..... Guess I'll have to break it up into pieces eh?

Also, the hardware store did not have a pressure gauge that would read
2000psi...... Hopefully I can stop by the welder's supply on the way
home. Right now all I have is a 0-200psi low quality gauge and a nice
little gauge for my regulator (0-160psi I think).

  #26  
Old January 24th 05, 05:09 PM
Morten
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"Elaine T" wrote in message
m...


HCl fumes badly in concentrated form, and I think I remember some fumes
from dilute HCl (haven't handled the stuff in a while). Same with
acetic acid for that matter. Wouldn't you tend to acidify the fishtank
some with acid fumes, or are they not concentrated enough to matter?


HCl does indeed fume a bit and so does the Acetic Acid (Vinegar), but the
acid is inside the ballon / drip bag inside the first container, and the
only way out of there is via ahose leading to the main reactor where it gets
neutralized / reacts with the baking powder and because you only draw off
the gas you should be fine. If you're to worried you could send the CO2 gas
through a bubble counter / water scrubber, that will take care of any stray
HCl / Acetic Acid molecules that might be in gas form inside the main
reactor.

So in fact there will be 4 containers, one which is open at the top with
water in it with a hose comming out of the bottom, the hose leads to the
acid in ballon container on the outside of the ballon, the hose from the
ballon goes through the bottom of the acid container and leads to the main
reactor which also contains the baking powder solution. From the main
reactor a small hose goes through a smaller container filled 2/3 with water
so that the co2 has to bubble through the water and out via another hose
above the water level and into tank diffuser / co2 reactor / valve /
whatever...


/Morten




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  #27  
Old January 25th 05, 03:57 AM
Dan White
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"spiral_72" wrote in message
ups.com...
An update:

I didn't have a drill and tap big enough for the pipe tap at home so
it'll have to wait untill I can di it at work. The cap is about 1 1/2 -
18 thread...... This is big but still much smaller than a chunk of dry
ice..... Guess I'll have to break it up into pieces eh?


Why not just melt the dry ice and pour it in? )

dwhite


  #28  
Old January 26th 05, 09:55 PM
spiral_72
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Well, for anyone still following this post:

The tank is finished for the most part..... I am kinda stuck on a plug
or lid for the top. I bought a 1-1/2 inch pipe plug to use but I am
having a difficult time finding a tap big enough for it...... I guess I
could order one, but that's about $30 for something I'll never use
again.

Construction is going very good...... As soon as I can decide what to
do about the plug/lid I'll weld the top on it and try out "da bomb"

Oh, 4 pounds of dry ice keeps only 2 days inside an Igloo cooler inside
your freezer.

  #29  
Old January 27th 05, 02:27 AM
Dan White
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"spiral_72" wrote in message
oups.com...
Well, for anyone still following this post:

The tank is finished for the most part..... I am kinda stuck on a plug
or lid for the top. I bought a 1-1/2 inch pipe plug to use but I am
having a difficult time finding a tap big enough for it...... I guess I
could order one, but that's about $30 for something I'll never use
again.

Construction is going very good...... As soon as I can decide what to
do about the plug/lid I'll weld the top on it and try out "da bomb"

Oh, 4 pounds of dry ice keeps only 2 days inside an Igloo cooler inside
your freezer.


So what altitude do you calculate your rocket will achieve after the plug
strips from the pressure? You'll have to subtract the energy loss due to
the cylinder ripping through your wall first, though.

dwhite --- still following this post!




  #30  
Old January 29th 05, 06:29 PM
Chameleon
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"Morten" wrote in message
...

"Elaine T" wrote in message
m...


HCl fumes badly in concentrated form, and I think I remember some fumes
from dilute HCl (haven't handled the stuff in a while). Same with
acetic acid for that matter. Wouldn't you tend to acidify the fishtank
some with acid fumes, or are they not concentrated enough to matter?


HCl does indeed fume a bit and so does the Acetic Acid (Vinegar), but the
acid is inside the ballon / drip bag inside the first container, and the
only way out of there is via ahose leading to the main reactor where it
gets
neutralized / reacts with the baking powder and because you only draw off
the gas you should be fine. If you're to worried you could send the CO2
gas
through a bubble counter / water scrubber, that will take care of any
stray
HCl / Acetic Acid molecules that might be in gas form inside the main
reactor.

So in fact there will be 4 containers, one which is open at the top with
water in it with a hose comming out of the bottom, the hose leads to the
acid in ballon container on the outside of the ballon, the hose from the
ballon goes through the bottom of the acid container and leads to the main
reactor which also contains the baking powder solution. From the main
reactor a small hose goes through a smaller container filled 2/3 with
water
so that the co2 has to bubble through the water and out via another hose
above the water level and into tank diffuser / co2 reactor / valve /
whatever...

Or you could bubble through a concentrated solution of NaOH which does not
fume and would last a lot longer than a pure water bubbler. A flask full of
NaOH pellets backed by some MgSO4 pebbles (to remove moisture from the gas
before it contacted the NaOH, which is hygroscopic) would also work.


 




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