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New type of DIY CO2 proposed

vahe at arminco_com wrote:

>I am thinking of designing a new type of DIY CO2 setup: using a bottle with
>dilute muriatic acid and pieces of marble in it. This should be cheap and
>can produce lots of CO2. Since marble is rather dense, and
>one can use very dilute acid, it can be set up so that the reaction will
>last for quite a period of time.
>Considering molar weights of used substances, well need 200 grams of
>marble and about 150 grams of HCl to produce one months worth of CO2. I
>guess, the substances can be filled in a 2 liter coke bottle,
>similarly as with the yeast method. Depending on the marble granule size
>and how dilute acid will be used, the reaction can be slowed down or
>intensified. I guess, the larger the granule size and the more dilute acid
>used, the slower will be the reaction. The output CO2 can be bubbled
>through a second bottle with chalk water (something like what people spray
>on the ceiling, but without glue added) to eliminate possible contamination
>of the output CO2 with acid vapors.

There are several problems:

1) HCl reacts very quickly with marble, so you will have regulate the HCl
(or marble) input to your reactor. How will you do this? A clock/screw feed
for the marble? A regulated drip for the HCl?

2) HCl is corrosive. The cardboard container for the plactic "milk jugs"
used for swimming pool HCl will detoriate just from the HCl diffusing
through the plastic bottle. HCl fumes will accelerate metal corrosion also.
Remember all the corrosion in your high school chemistry lab?

3) HCl is dangerous. If you spill it on your skin and wash it off quickly,
it ain't too bad, but don't splash it in your eyes.

4) Think of the failure mechanisms.
  a) Explosive failure of the reaction chamber with HCl all over you and
your house.
  b) Excessive reaction rate with CO2 poisioning of your fish.
  c) Accidental spill or splash of HCl.
  d) Injection of HCl into your tank.

Please let us know how you will solve the engineering problems.