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Re: Acid+dolomite CO2 generator

On Fri, 11 Jun 1999, Bob Wurster wrote:


> >bottom of the dolomite container.  As for starting the drip, I'm still
> >thinking about that one.

> I'm not keen on the acid/dolomite idea, but I do have a method for getting
> it going. Start the drip with water instead of HCL.

I guess I don't see a problem with starting the drip.  The acid reservoir
would be entirely above the generator and it would be connected to the
generator by tubing from both the top of the reservoir and the bottom of
the reservoir.  There would be a valve on the tube from the bottom of the
reservoir to the generator.  When the valve is opened, the acid would

I don't see how you could start that with water and later switch to acid.

Further, about HCl as gas.  I think I might try using sulfuric acid
rather than hydrochloric.  If you dilute the hydrochloric to avoid
contaminating the CO2 with HCl gas, then you end up using more acid to get
the job done.  Getting rid of the waste CaCl2 solution is already a
problem, and using a dilute acid makes that problem worse.

With sulfuric acid the only limitation I can think of is that it has to be
sufficiently dilute so that the CaSO4 solution you get from the reaction
doesn't start precipitating CaS04.2H2O (gypsum).  If you use real dolomite
chips this is less of a problem then if you use limestone chips, as the
dolomite will result in a solution that is 50% MgSO4 and 50% CaSO4 (mole
%, not weight), rather than 100% CaSO4.  The MgSO4 is very soluble.

Still further, list members have commented before that bottled CO2 seemed
to dissolve more readily than yeast-CO2.  That caused some question about
just how pure the yeast-CO2 was.  After some thought, I realized that the
yeast-generated CO2 is probably saturated with water vapor, and the
bottled CO2 is dry.  I ran a quick model to see how much difference this
might make to how long it took to dissolve a small bubble, and it made
about a 10% difference - possibly larger or smaller depending on how big
the bubble is to start with.  A 10% difference is probably observable.

If this is a problem, then the dolomite+acid generator might have an even
larger problem that way.  The reaction that makes the CO2 also makes
water, and since the reaction generates heat the resulting CO2 + water
vapor will be slightly warm, and will cool off before it gets into the
tank, possible causing water to condense inside the tubing.

I've considered running my yeast-generated CO2 through a drying chamber
with silica gel or CaCl2 to see if it makes a difference.  Has anyone else
done that and noticed a difference?

Yet further, are there other reactions that might be safer or more
convenient to work with than dolomite+acid?  I was wondering if
bleach+sugar solution might generate CO2.

Roger Miller