Structural Correlations in Alums

The crystal data for 57 S04, Se04 and BeF4 alums of a and p type, with a general formula MIMIII(XY4)2 ■ 12H120, were extracted from literature. Multiple linear regression was employed in order to establish a correlation between the length of the unit cell axis (dependent variable) and (1-2) the effective ionic radii of both M+ and M3-; (3) the mean X-Y distance; (4) Pauling\u27s electronegativity of atom Y; (5) the alum type; (6) the orbital quantum number of M3+ ion and (7) the number of d-electrons in the highest energy shell. The adjusted r2 statistics had a high value (0.986), thus enabling the use of the regression equation for predictive purposes. The effective ionic radii for CH3NH3, NH3OH+, N2HJ and ions were calculated in this way. Some notes on the stability and existence of particular alums are also given