Topochemical transformations of cyclotriphosphates of alkali metals and ammonium

Abstract

The isothermal and nonisothermal conversions of hydrated and anhydrous forms of cyelotriphosphates of sodium, lithium and ammonium were investigated in different gaseous atmospheres and in vacuum. It was shown that gaseous ammonia in its mixtures with water vapour can accelerate the solid-state splitting of the anionic cycle. A mechanism is suggested for the decycling effect of gaseous ammonia and its mixtures with water vapour.Despite the large number of publications on the transformation of condensed phosphates, the literature contains practically no information on the influence of temperature and the gas atmosphere composition on the process of the solid-phase decyclization of cyclic triphosphate anions. This report describes a study of the topochemical transformations of the cyclic triphosphates of sodium, Na3P309"xH20 (x = 1, 3, 6), lithium, Li3P309"3H20, and ammonium, (NH4)3P309, in an atmosphere of air, in vacuum, in ammonia and in mixtures of ammonia and water vapour.When heated in vacuum, in a water vapour atmosphere or in air, sodium cyclotriphosphate tri-and hexahydrate lose crystalline water, mainly below 100 ~ the hexahydrate under going dehydration without anion ring breakage and without crystallization of the intermediate phases, while for the trihydrate there is similarly no ring breakage, but the intermediate monohydrate undergoes crystallization.When the monohydrate is heated under the same conditions, water is removed at above 100 ~ in two stages, with corresponding endoeffects at 128 and 210 ~ . Within the given temperature range, and especially in the second stage, the dehydration is accompanied by decyclization of the anion, which results in amorphous products. The decomposition degree is comparatively low, the content of phosphorus in the cyclotriphosphate form not falling John Wiley & Sons, Limited, Chichester AkadOniai Kiad6, Budapest