Ion Exchange in Molten Salts. II: The Occlusion of Lithium, Sodium, Potassium and Silver Nitrates in the Respective Forms of Zeolite A.

The occlusion of lithium, sodium, potassium and silver nitrates from the anhydrous melts in the respective zeolites has been studied by measuring the gain in weight and by direct analysis. The results in moles of occluded nitrate per formula weight of zeolite M₁₂^I[(AlO₂)₁₂(SiO₂)₁₂] are 11.7 for LiNO₃, 10 for NaNO₃ and 10 for AgNO₃ and essentially zero for KNO₃. A model is proposed for the structure of the occlusion compound Na₂₂[(AlO₂)₁₂(SiO₂)₁₂(NO₃)₁₀], in terms of four Na_I⁺ ions and four [Na_I ‐ NO₃ ‐ Na]⁺ groups at the apexes of the cubic unit cell and four [Na_II ‐ NO₃ ‐ Na]^+1/3 groups coordinated with two [NaNO₃]^−2/3 groups at the faces, to explain the properties of the occluded zeolites.