I am doing an experiment with plants that involves exposing them to air without carbon dioxide. Soda lime does absorb carbon dioxide but I do not have any available. Wiki provides a recipe (sort of) but I’m not sure if I mix the ingredients or if some chemical change is needed. Can I make soda lime? Is there another way to remove carbon dioxide from air?
You’ll end up with a gooey mess if you just mix the hydroxides with water in the proportions given by wikipedia, while commercial soda lime is made of nice pourable granules.
You’d probably be better off bubbling your air supply through a solution of 5M sodium hydroxide. If you don’t have a proper sparging setup, you can make one with a graduated cylinder, some tubing, a stopper and an aquarium bubbling stone.
Of course your CO[sub]2[/sub] deprived plants will respire and produce their own CO[sub]2[/sub], so unless you constantly filter the air RuBisCO will continue to fix carbon.
It might be simpler to mix up your own version of air, without the CO[sub]2[/sub]. Nitrogen (78%), oxygen (21%) and argon (around 1%) - all readily available in bottles - will pretty well cover it. No other gas is more than about 1 part in 10,000.
When I was a kid, I used quicklime (calcium oxide) or slaked lime (calcium hydroxide), both of which were available cheaply in technical grade (along with inert substances like sand, alumina, rust or magnesium oxides. Slaked lime is basically the hydrated version of quck or burnt lime, and is the active ingredient in soda lime.
You can get quicklime or slaked lime from many sources: garden shops, large hardware stores, cement mixing plants --and nowadays, the food grade version called “cal” is widely available for home tortilla makers. Almost every city has a local tortilla factory that will sell you a few pounds very cheaply out of their bulk stock (but don’t let “food grade” make you careless: the stuff is still dangerous, if taken directly internally vs. used sparingly in food prep, where it is largely neutralized and/or washed out before consumption)
Calcium hydroxide is less caustic than soda lime, which includes the more potent sodium and potassium hydroxides as well. Slaked lime can also be largely regenerated several times for reuse by baking at kitchen oven temperatiures. Soda lime may regenerate bettter (I’m guessing) due to the excess of stronger hydroxides, but though lye and potash lye (sodium and potassium hydroxides, respectively) were readily available, I didn’t feel any need to add them: a 25 lb bag of lime lasted me years.
Personally, I used a “bubbler” filled with a water solution of slaked lime (which became hydrated lime). It took a little more work than a dry system might have, but it was really fairly minimal, and the system worked very well, extracting even trace amounts of CO2 in just one or two passes. A solid powder would be MUCH less efficeint per pass.
Sorry I meant to say that I forced air through several layers of stainless streel mesh or two inches of fluffed glass wool (fiberglass should also work well) produced a very fine "mist of bubbles, so the old term “bubbler” might be misleading. My device was more an “aerator”, as seen in kitchen faucets, than a bubbler seen in aquariums
I personally found that stainless steel screens/mesh worked more reliably, and required less precautions than glass wool of fiber glass, but since lime water is somewhat corrosive to metals, especially over time, and you shuld probably wear gloves and an inhaler when working with the various lime powders and solutions anyway, to meet today’s safety standards, it might be a toss-up for you. Do what works best for your container. Mine was mase by cutting and glazing a 5-gal glass jug, but if I had to do it today, I’d use a 5 gal plastic bucket, preferably polyethylene, which is lighter and easier to cut/melt, and seal it with silicone gasket material – both are cheap and readily available.
Can I take a plant potted in soil, pour quicklime on the soil, wrap the whole thing in plastic wrap and assume that the carbon dioxide will be absorbed?