R. L. Davidovich

A Study of Redistribution of Fluorine Ions Between Al3+ and Be2+ By Means of 19 NMR

Abstract In the system Al(NO3)3 - NaF - H20, 19F NMR was used to findI the existence of AlF2+ and AlF+ 2 with chemical shifts of 587.5 and 587.0 p.p.m. in relation to F2. Fluorine ion exchange between these two forms impeded identification of certain signals in the spectrum. Matwiyoff and Wageman2 recorded the simultaneous presence of three signals in the I9F NMR spectrum and assigned them to three forms of aluminum: AlF2+, AlF+ 2 and AlF3. Squilibrium constants were calculated for the reaction The 19F NMR method was used to establish that in aqueous solutions of (NH4)2BeF4 hydrolysis takes place3 leading to formation of BeF3 (H2O)−. An instability constant, equal to (8.6 ± 2.0)*I0−2, was calculated for the reaction BeF2 4 ⇄ BeF− 3 + F−. Introduction of a hard4 Be2+ acid into an (NH4)2BeF4 solution caused the collapse of signals related to BeF2− 4 and BeF− 3, shifting the exchange signal to a high field, This may be explained by increased hydrolysis and appearance of beryllium forms with lower fluorine co...