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I'm not chemist, and I'm looking for easiest way to measure how much oxygen plant in closed container will produce per hour [can measure over time for increased accuracy].

My first idea was to measure percentage of oxygen in air with automotive lambda sensor.

However I don't expect good precision of measurement like this, and this is a little complicated (lambda sensor needs high temperature, so I need to heat it up).

I wonder if there is some chemical way to perform measurement like this.

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  • $\begingroup$ Possible duplicate of this question? Different application, I agree. $\endgroup$ – bobthechemist Jul 19 '13 at 9:06
  • $\begingroup$ Thats pretty hard to do... Produced water will condensate everywhere... And its pretty hard to light it up in closed jar (but not impossible). Im wondering about purchasing oxygen sensor for $70 and making electronic circuit for it. I thought there is simple reaction with some powder that will absorb oxygen in few minutes and change its mass or something. $\endgroup$ – Kamil Jul 19 '13 at 9:22
  • $\begingroup$ If easy is important, then purchasing a sensor is the way to go. DIY solutions probably require a bit of Chemistry knowledge and materials (e.g. platinum) that might end up costing as much as a commercial product. $\endgroup$ – bobthechemist Jul 19 '13 at 9:33
  • $\begingroup$ I edited my question. Maybe measuring carbon oxide is easier? $\endgroup$ – Kamil Jul 19 '13 at 9:45
  • $\begingroup$ Unlikely, the amounts of gases produced are very small. You might benefit from a web search of "how to measure plant respiration" all of the non-high-tech methods use either water traps or commercial probes. $\endgroup$ – bobthechemist Jul 19 '13 at 10:06
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This is untested, but I think it might work. You could light some fuel on fire inside the closed container and see how much of it burns (just put the cup of fuel on a kitchen scale) before it dies out and than back calculate how much oxygen was present. Preferably you should take a fuel that burns easily to make sure that the total combustion reaction is the only reaction that occurs. Also if you want to repeat the experiment every hour or so, you want to be sure that the fuel does not evaporate (substantially) because that might cause the entire container to light up when you try to burn the fuel.

I am not really sure which 'household' fuel would be a good option, but maybe one of the other people on this site have suggestions?!

You can probably use one of those candle lighters and stick the long side through a small hole in your container and than seal the rest of the hole to be able to light a fire inside, without having air flowing in or out.

Just be careful not to set the plant (or anything other than the fuel) on fire!

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  • $\begingroup$ I think some alcohol would be right choice, however I think this will be very imprecise measurement. Other idea is propane mini-torch with constant pressure. Time of burning in constant flow should be proportional to amount of oxygen... $\endgroup$ – Kamil Jul 19 '13 at 8:58
  • $\begingroup$ Other idea - "alcohol candle" made of probe, plug (to reduce evaporation) and some kind of candlewick in little hole in plug. $\endgroup$ – Kamil Jul 19 '13 at 9:06
  • $\begingroup$ @Kamil - what are your main worries in the imprecision? local depletion of oxygen? or something else? $\endgroup$ – Michiel Jul 19 '13 at 17:01
  • $\begingroup$ Im worried, that amout of burned fuel (alcohol) will be very small. I can minimize local depletion by some fan if convection from flame will be not enough (in case of big container, like terrarium or something). $\endgroup$ – Kamil Jul 20 '13 at 12:08

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