CO gas is absorbed in ammoniacal CuCl or I2O5.
Unsaturated hydrocarbons are absorbed in Br2 solution or fuming H2SO4.
O3 is absorbed in Turpentine oil.
CO2 is absorbed in NaOH or KOH.
SO2 is absorbed in NaOH or KOH.
O2 is absorbed in alkaline pyrogallol or yellow phosphorous.
H2 is absorbed in colloidal palladium solution.