Alkali aluminates atoms

Aluminum is an amphoteric element that acts as a nonmetal in alkali and develops a hydrated gelatinous aluminate of a species [Al(OH)4]. As a result of this reaction, certain suspended matter including polysaccharide polyanions coprecipitates by entrainment. This element, applied in atomic or ionic form, is a common technique for commercial isolation of pectin. In acid, Al3+ supposedly neutralizes polyanions to yield the aluminum salt. After precipitation of the pectin-aluminum complex, the metal ligand is removed by acidification and washing. 

Incomplete atomization of the analyte causes so-called chemical interferences. They are due to the fact that atomic absorption can only occur with free atoms. Thus reactions in the flame which lead to the formation of thermally stable species decrease the signals. This fact is responsible for the depression of calcium signals in serum analysis by the proteins present, as well as for the low sensitivities of metals that form thermally stable oxides or carbides (Al, B, V, etc.) in flame AAS. A further example of a chemical interference is the suppression of the absorbance of earth alkali metals as a result of the presence of oxyanions (X) such as aluminates or phosphates. This well-known calcium-phosphate interference is caused by the... 

AICI3 reacts with the chloride salt of the alkali metals and forms the corresponding alkali metal tetrachloro aluminate complexes (ref.26). The aluminium atoms of these complexes exhibit a chemical shift of ca. 100 ppm (refs.29,33) with respect to aqueous sodium aluminate. HCl and AICI3 are formed during dealumination of HY zeolites (ref.28). 

The reaction of SiCl4 with LiY, NaY and HY zeolites at temperatures below 423 K leads to the formation of framework-bound SiC13 species and LiCI, NaY and HC1, respectively. The SiCls species exhibit a 29 MASNMR resonance at ca. -45 ppm. The MASNMR spectra of the zeolite samples at this stage of the reaction show the presence of aluminium in distorted tetrahedral environments. Upon heating of the zeolites to temperatures exceeding 423 K, the Si atoms of the SiCl3 species are inserted in the framework, while the A1 atoms are released as AICI3. The latter is transformed into alkali metal tetrachloro-aluminate complexes in presence of alkali metal chloride salts. 

---