Re: Help with trapping CO2 in soda lime

This really isn't my area of expertise and I have not personally performed this assay. In my mind you should make a column (tube with closed ends) filled with soda lime and then pass a known volume of air through the column. I guess that the balloon method could work, but we've have to do the calculations.

The soda lime will absorb CO2 and also make water that will evaporate on drying.

A mole of gas is 22.4 liters and for CO2 would weigh 44 g. Now, the atmosphere is not pure CO2; it is closer to 0.03%. Thus to get a mole of CO2, you would need to pass about 75,000 liters through the filter. Let's say that you scale down to 0.1 mole, that would be only a 4.4 g difference, minus the weight of the water lost.

The soda lime can only efficiently absorb CO2 up to about 7% of its weight. So to capture a mole of CO2, you would need 628 g of soda lime. Again, you could scale this down. The baking, exposure, baking pattern you are using is valid. However, whatever difference you get in weight needs to be multiplied by 1.69 to account for the water released.

You can do the caluclations from here. Recognize that if you are looking for small changes in CO2 in different areas, this could be difficult to pick up. You would have to do many measurments with different columns and then perform statistical analyses to show that any differences are significant.

Hope this helps.

Happy Kringle.

Mark.