Mechanism and kinetics of formation and decomposition of carnallitic double salts

Insufficient thermochemical data are available on the carnallitic double salts M¹MgX ₃·6H₂O (M=Li (H₂O), K, Rb, Cs, NH₄;X=Cl. Br, I). In the present work, findings relating to the salt paragenesis are given on the basis of solution-calorimetric measurements. The melting and decomposition behaviour is characterized by means of DTA and thermogravimetric investigations under quasiequilibrium conditons. Except for Li(H₂O) Cl·MgCl₂·6H₂O, the decomposition of the chloridic carnallitic double salts always proceeds via the intermediate stage of the corresponding dihydrate. For each of the different anions, a linear correlation is found between the degree of hydrolysis of the hydrate water-free final products and the radii of the monovalent cations.