hodges
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How to Measure CO2 Concentration in Air?
Does anyone have any ideas how I could measure, to within a few percent accuracy, the amount of CO2 in the atmosphere? I would like to do my own
measurements of changes in CO2 concentration in the atmosphere with seasons and with time.
One "brute force" way I can think of might be to bubble a known amount of air through a basic solution such as NaOH and measure the amount of mass
increase. However, since some of the solution would evaporate, it would be necessary to dry the resulting product to determine an accurate mass. Big
unknowns would be the percentage of CO2 from the air that actually reacts, and what the final compound is (bicarbonate vs carbonate vs compounds based
on other chemicals in the air).
Any ideas for this or other methods?
Thanks,
Hodges
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12AX7
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Use concentrated Ca(OH)2 solution and weigh the precipitate. 
Tim
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BromicAcid
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In my quant class the method of measuring CO<sub>2</sub> in the air was covered. The exact method escapes me but there was something
about drawing air over asbestos plates coated in NaOH and doing something with them, sorry that I don't recall any details, my quant book was one of
the few chemistry books in my life that I felt the need to sell.
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IrC
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I would look into Figaro gas sensor IC's, add an op amp or two and make you a nice little circuit with real time readout. The CO sensor is only around
11 buckaroos, I once build a CO warning meter with alarm and it worked so well. The circuit is typical for their products and you can find it online
around, or in app notes right at Figaro. Don't know if they have a CO2 sensor but I imagine they do, they make them for about every gas.
One caution, burned and especially unburned hydrocarbons will saturate the sensor even with no detected gas around, too much in the way of raw fuel
gasses and your sensor will be DOA. Not much power to run, little heating element to clean the sensor which is handy. Check into it, by far the easy
way to do what you want.
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S.C. Wack
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Fairly accurate chemical method article on hand:
Attachment: jacs_25_150_1903.pdf (531kB)
This file has been downloaded 654 times
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hodges
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| Quote: | Originally posted by S.C. Wack
Fairly accurate chemical method article on hand: |
Thanks! This seems like the way to go. I wonder if calcium hydroxide could be used in place of barium hydroxide.
What I get from the article is to use a weak solution of a base which forms an insuluable carbonate, and expose this to a known amount of air. The
precipitated carbonate is then filtered out, and the remaining solution titrated to determine how much of the base is left. This allows calculation
of how much carbonate was formed, and thus how much CO2 was in the sample.
This procedure sounds easy enough; the hard part being to ensure purity of the water used (from dissolved CO2) and avoiding contamination from the
container.
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unionised
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"Use concentrated Ca(OH)2 solution and weigh the precipitate.
Tim "
In what solvent?
Water only disolves 1 or 2 g/litre.
Ba(OH)2 is much more soluble; but also more toxic. The method we use at work is based on BaCO3 ppt.
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gsd
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I believe "Orsat Apparatus" is a fairly standard way to go about it.
Following link may be useful:
http://www.dpi.vic.gov.au/dpi/nreninf.nsf/9e58661e880ba9e44a...
[Edited on 26-2-2006 by gsd]
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12AX7
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| Quote: | Originally posted by unionised
"Use concentrated Ca(OH)2 solution and weigh the precipitate.
Tim "
In what solvent?
Water only disolves 1 or 2 g/litre.
Ba(OH)2 is much more soluble; but also more toxic. The method we use at work is based on BaCO3 ppt. |
Yeah, but BaCO3 and CaCO3 are both much less soluble than the hydroxides, so it'll work either way. Besides, there isn't much CO2 in a generic
"sample" of air, so it won't take much hydroxide.
Ba(OH)2 is certainly more soluble, so you can use less solution.
Tim
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JohnWW
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Yes, I was hoping someone would mention the Orsat Apparatus. I once used it to analyse flue gas coming from the distillation furnace of an oil
refinery. I think the apparatus and method is also described in Vogel's Quantitave Inorganic Chemical Analysis.
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Texium
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Thread Moved
19-11-2023 at 11:04 |
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