Please help! Maintaining constant concentrations of CO2?

[acuriousperson]

Hi,
I am interested in doing a science research project that would measure the effects of different concentrations of atmospheric CO2 on plants. I was wondering if there is any possible way to regulate the amount of CO2-- since the plant would most likely be constantly taking up the CO2, how could I make sure that the concentration of CO2 is constant? Would I need a large container for the plants? What could I do to maintain CO2 concentrations?
Help would be greatly appreciated!
Thank you!

[ScienceExpert123]

Dear acuriousperson,

Thank you for contacting science buddies' ask an expert. Reguarding your question, there are a few possible ideas that I can think of:
1. You can purchase a CO2 incubator and control the intake of CO2 using the incubator. (CO2 incubators are quite expensive ranging from a few hundred to a few thousand dollars). You might want to consult scientists at a local college/university and ask them if you can use their incubator for your experiments.
2. You can purchase dry ice (solid CO2) and weigh different amounts of the dry ice which equals different amounts of CO2 gas (if you do this make sure you use highly insulated gloves because dry ice exists at −110°F and if the dry ice touches your skin it will burn your skin off). Once you weigh your dry ice you can put it into a sealed container (make sure that the container is several times larger than the piece of dry ice) and let it turn back into CO2 gas. You can then place the plant inside the container. I know that this method doesn't give a continual flow of CO2 gas, but if you kept adding dry ice the plant would probably freeze.

good luck,
scienceexpert123

[deleted-71417]

Hi,

I am happy you already have one answer to this question, because my attempts to find a good answer were only marginally successful. I hope you find crumbs of usefulness in the following:

I suspect the simplest way to maintain a “constant” Carbon dioxide concentration in gas is to have the gas in constant equilibrium with a relatively large amount of carbonate- bicarbonate buffer solution. If you add a pH indicator dye to the buffer solution, a change in color of the buffer solution will indicate a change in carbon dioxide concentration (indicating a possible need to change or replace the buffer solution. You can control the concentration of carbon dioxide at equilibrium with the buffer by adjusting the pH of the buffer. You will have most control when the concentration of bicarbonate and carbonate are about equal., meaning the pH is about equal to the pKa of the carbonate bicarbonate equilibria.

Here is a google book review link that may help:

http://books.google.com/books?id=RvQVCh ... t#PPA33,M1

You may also be interested in another Science Buddies thread about monitoring carbon dioxide levels in containers with living plants:

https://www.sciencebuddies.org/mentorin ... =25&t=4063

Also an obscure discussion of bicarbonate-carbonate equilibria:

http://fins.actwin.com/aquatic-plants/m ... 00218.html

And a slightly more useful discussion of carbon dioxide bicarbonate equilibria:
http://books.google.com/books?id=Vh6tFT ... t#PPA48,M1

And

http://www.geo.uu.nl/Research/Geochemis ... iation.pdf


Good luck with the project!

Barrett Tomlinson