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 '__

"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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"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.