SYNTHESIS OF CYCLO-TETRAPHOSPHATES NI2-XMGXP4O12

The tetrametaphosphates of the type Niz-xMgxP4O12, where x = 0 to 2, have been synthesized as new binary compounds, and their existence has been proved. The synthesis is based on a thermal procedure making use of the reversible transformation of tetrametaphosphates to higher linear phosphates. Temperatures of formation of these products have been determined (i.e. formation by thermal recrystallization from higher linear phosphates) which decrease with increasing magnesium content, x. The structure of the binary tetrametaphosphates belongs to the monoclinic system (over the whole range of x); the structural parameters determined slowly increase with increasing magnesium content. With respect to the proposed application of these products as inorganic pigments, the following properties have been determined experimentally: density, thermal stability and colour.