Making your own ultra low oxygen CO2
Posted: Fri Sep 09, 2016 8:03 pm
It might be possible to make one’s own, essentially oxygen free, carbon dioxide by simply placing some form of oxygen scavenger into a pressure capable container such as the ubiquitous corny keg and filling to max pressure with commercial grades of CO2. Theoretically all free oxygen should be scavenged given enough time. First thought was off the shelf oxygen packets but the idea of iron and salts possibly contaminating the gas or causing corrosion in the stainless pressure vessel are worrisome. Also the iron oxide forming reaction might not proceed to low enough percentages before coming to a halt.
So why not just use our old friend metabisulfite in solution. I would think it would not require more than a liter of water and maybe 5 grams of either Na or Kmeta, just enough to get a decent contact area. The CO2 pressure in the container should just speed up this process. The release of SO2 might be of concern however one could add an amount of sodium carbonate that would combine with the SO2 forming more sodium bisulfite and CO2 under the reaction: SO2 + Na2CO3 --> Na2SO3 + CO2. Although I’m uncertain how this would be effected by the carbonic acid formed from CO2 in solution. The exhaustion of scavenging capacity would be signaled by evolution of SO2. Certainly some SO2 in the vessel would keep stray biological organisms from making a home and one should be able to re-pressurize the container many times before exhausting its ability to get the oxygen.
The volume of gas you could process at a time would be small in comparison to what you can tap off a standard CO2 cylinder. A simple way increase the volume of course is to employ a larger keg, possibly one that has been repaired or has unsanitary welds since that would not matter for this use and be cheaper to boot.
This is all just theory at this point but I welcome any opinions on the idea.
So why not just use our old friend metabisulfite in solution. I would think it would not require more than a liter of water and maybe 5 grams of either Na or Kmeta, just enough to get a decent contact area. The CO2 pressure in the container should just speed up this process. The release of SO2 might be of concern however one could add an amount of sodium carbonate that would combine with the SO2 forming more sodium bisulfite and CO2 under the reaction: SO2 + Na2CO3 --> Na2SO3 + CO2. Although I’m uncertain how this would be effected by the carbonic acid formed from CO2 in solution. The exhaustion of scavenging capacity would be signaled by evolution of SO2. Certainly some SO2 in the vessel would keep stray biological organisms from making a home and one should be able to re-pressurize the container many times before exhausting its ability to get the oxygen.
The volume of gas you could process at a time would be small in comparison to what you can tap off a standard CO2 cylinder. A simple way increase the volume of course is to employ a larger keg, possibly one that has been repaired or has unsanitary welds since that would not matter for this use and be cheaper to boot.
This is all just theory at this point but I welcome any opinions on the idea.