3 years ago
If you want to do it electronically, there are sensors for it.
Well, if simply want to detect the presence of carbon dioxide in a gas sample, you can just bubble the gas sample through some lime (Ca(OH)2) water. The presence of a cloudy precipitate, i.e. insoluble calcium carbonate CaCO3, indicates the gas has carbon dioxide in it.
This test is shown in cartoon form on page 31 of Bob Brent's classic Golden Book of Chemistry Experiments, available for free, here,http://library.sciencemadness.org/library/books/Br...
and probably other places too.
If you want a test that is quantitative, i.e a test that tells you how much CO2 is in a gas sample, you might be able to come up with something using gravimetric analysis. By that I mean a reaction that will give you a measurable change in mass.
For example if you were making enough calcium carbonate precipitate to notice a mass change in your absorber vessel, (or filter, then dry, then weigh the precipitate) then maybe you could use that figure out how much CO2 was in the gas sample, although it might have to be a really big gas sample, to get enough mass change to measure.
Anyway, slaked lime,
is pretty cheap stuff. It is used to make mortar, and also for some kinds of food preparation. I would naively guess the kind sold for food use is more pure.
By the way, there are a number of other reactions that will change CO2 to a solid carbonate or bicarbonate. Sometimes the phrase "carbon dioxide scrubbing" is used to describe processes of this kind.
So if you follow those links, you might find a reaction that will work for your thing.
Another reaction that comes to mind, is one of the steps in the Solvay process,
NaCl + CO2 + NH3 + H2O = NaHCO3 + NH4Cl
because table salt and ammonia water are pretty cheap and easy to find too.
What exactly do you want to measure? The % Co2 in some mixture of gasses?
About as cheap as you will get if you want accuracy AND you will have to interface to a microprocessor and display to see the results.