Sorption of Anhydrous Ammonia by Dry Clay Systems

NH 3 sorption and/or retention over the pressure range of 0 to 100 ml. of mercury by dry bentonite, halloysite, and synthetic gibbsite was investigated using a manometric technique employing equilibrium measurements in a special sorption apparatus. Chemisorbed NH 3 is believed to be that which has gained a proton and undergone exchange reactions with the exchangeable cations and that which has reacted with the weakly dissociated hydroxyl groups of the lattice edges. The differential influence of saturating cations is believed to be due, at least in part, to the differences in degrees of hydration of these ions. Possible mechanisms of sorption are proposed. There were no differences in amounts of NH 3 sorbed and chemisorbed by Ca‐bentonite adjusted to pH 8, 9, and 10. This lack of influence is explained on the basis of the pH range involved and the mechanisms of sorption. The failure of synthetic gibbsite, Al(OH) 3 , to chemisorb NH 3 is explained by the basic nature of the mineral.