CO2 for plant food

Douglas Wiggins (
Sun, 5 Mar 1995 21:30:00 GMT

This is my third attempt to send this to:

Brett Lymn

BL:'Twas me that wrote the suggestion about the yeast + water for CO2

And 'twas me that wrote the suggestion about using CO2 in the first
place (only the discussion has changed a lot from when I was
mentioning tanks and solenoids; now it is going from home-brew to
mini-labs . . . next someone is going to suggest raising rabbits).

BL:According to Doug Bosco:
BL:>experiments was adding vinegar to baking soda, generating lots of suds and
BL:>CO2. Maybe this is a good method of generating CO2. It involves two common


BL:The problem is that the reaction is a bit too fast, all the reagents

You did mention some ways that this might be rigged, such as by
dripping, that would be valid (old time miners had head-lamps which
relied upon acetylene gas which was generated by water dripping
upon calcium carbide - it is practical), but, when you were
studying chemistry, did you ever see something about generating CO2
from limestone? Marble and limestone are made of the same thing,
and they will react with acid to form CO2 - the rate of the
reaction will depend upon the strength of the acid and upon the
material it is working on - marble will be slower than limestone -
but this reaction rate will be slower, in any event, than the rate
of reaction of vinegar and baking soda. Other factors which would
affect the rate of the reaction are temperature and the size of
the chunks of solid material. Of course, if the rate of dripping
the acid onto the material to be reacted could be controlled well
enough, it wouldn't matter how fast the reaction occured - vinegar
and baking soda could be used, if the vinegar were dripped slowly
enough - some chemistry equations might be called-for to determine
how much baking soda needs to be reacted in order to "feed" a
terrarium of a given size.

It was an excellent suggestion, to use chemicals, and I believe
that something could be made with marble chips or lumps of
limestone, and the acid could be diluted until it provides just the
right amount of discharge - perhaps with a bit of stronger acid
dripped slowly into the container to replace that which has been
reacted. Be sure to use the correct materials when building
something to handle acid, though - use only plastic or glass, and
keep metal away from the fumes. I have no idea what it would cost
if vinegar were used, but swimming pool acid, while very dangerous,
is also very cheap; I would suggest diluting* it down to working
strength before bringing it into the house, that strength
determined by adding it to your rocks and seeing if that is how
fast you want it to fizz. If you want to figure out how much gas
you need to produce: you want to raise the level of CO2 in the
terrarium to about 500 PPM, and up to 1000 PPM would be OK.

***ALWAYS add the acid to the water when diluting; use this saying
to help remember: "If you do things as you oughtta, add the acid to
the watta" - forgive the intentional misspelling; it could just as
well be "oughter" and "water" - whatever feels right to help you
remember what to do.

I would like to say, again, how much I appreciate the growth
enhancement caused by regular atmospheric injections of CO2 -
Andrew Marshall in Seattle was moaning and griping about the
creepin' crud fungus that was eating his cephalotus, and was
concerned about selling me some with the infection, but a few days
in my terrarium and the fungus was gone and the plants were

I just hope that nobody poisons their plants by some of the
experiments that this conversation might provoke. It might be a
good idea to use a trap before the terrarium if using concentrated
acid, as acid fumes can be carried by the air. This trap is made by
putting a tube from the reaction jar into a jar containing steel
wool, and a tube from the bottom of this jar goes to the terrarium
- this is only one design, but it should work well enough; if water
is used in the trap, as is a common practice, the tube dipping into
the water comes from the reaction flask, and if it dips too deep,
and if there is not much acid left in the dripper portion, the gas
may push up through the acid rather than through the water.

-Douglas Wiggins, Portland, Oregon

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