... heating under high vacuum.3A (pore size 3 Å): Adsorbs NH3, H2O, (not C2H6), good for drying polar liquids.Molecular Sieve 3A ... nitrogen and water can diffuse. 4A (pore size 4 Å): Adsorbs H2O, CO2, SO2, H2S, C2H4, C2H6, C3H6, EtOH. 4A oecular sieve ...