Soda-lime is a granular solid produced by slacking quicklime (CaO) with a concentrated solution of sodium hydroxide, NaOH(aq). In chemical reactions, soda-lime acts as sodium hydroxide but, unlike sodium hydroxide, it is not deliquescent and does not attack glass.
Soda lime reacts with CO2 being respired by the organisms in the soil. The change in the weight of the soda lime over the 48-hour incubation period can be used to estimate the amount of CO2 respired by the soil microbes and other organisms.
The size of soda lime granules is important. If granules are too large, the surface area for absorption is insufficient; if they are too small, the narrow space between granules results in a high resistance to breathing.