Aluminium ions

The aluminium ion, charge -I- 3. ionic radius 0.045 nm, found in aluminium trifluoride, undergoes a similar reaction when a soluble aluminium salt is placed in water at room temperature. Initially the aluminium ion is surrounded by six water molecules and the complex ion has the predicted octahedral symmetry (see Table 2.5 ) ... 

The following mechanism appears reasonable (compare Section VI, 12), It assumes that the function of the aluminium ieri.-butoxide, or other alkoxide. is to provide a source of aluminium ions and that the aluminium salt of the secondary alcohol is the actual reactant. Aluminium with its sextet of electrons has a pronounced tendency to accept a pair of electrons, thus facilitating the initial coordination and the subsequent transfer of a hydride ion ... 

Alexandrite, like ruby, contains Cr ions but they are substituted in the lattice of chrysoberyl, BeAl204. The chromium ions occupy two symmetrically non-equivalent positions which would otherwise be occupied by aluminium ions. In this environment the 2 ground state of Cr is broadened, compared with that in ruby, by coupling to vibrations of the crystal lattice. 

Radiochemical studies indicate that the pore base is the actual site of formation of aluminium oxide, presumably by transport of aluminium ions across the barrier-layer, although transport of oxygen ions in the opposite direction has been postulated by some authorities. The downward extension of the pore takes place by chemical solution, which may be enhanced by the heating effect of the current and the greater solution rate of the freshly formed oxide, but will also be limited by diffusion. It has been shown that the freshly formed oxide, y -AljOj, is amorphous and becomes slowly converted into a more nearly crystalline modifipation of y-AljO . 

Repeat the determination with a solution containing 100 jig of iron(III) and of aluminium ion the absorbance is unaffected. 

Repeat the experiment using 50.0 mL of the iron(III) solution in the presence of 100 fig of aluminium ion and 100 fig of nickel ion at pH 2.0 (use a pH meter to adjust the acidity) and measure the absorbance. Confirm that an effective separation has been achieved. 

Repeat the experiment in the presence of 500 jug of iron(III) and 500 jug of aluminium ions no interference will be detected, but cobalt may interfere (Note 2). 

Pipette 25 mL of an aluminium ion solution (approximately 0.01 M) into a conical flask and from a burette add a slight excess of 0.01 M EDTA solution adjust the pH to between 7 and 8 by the addition of ammonia solution (test drops on phenol red paper or use a pH meter). Boil the solution for a few minutes to ensure complete complexation of the aluminium cool to room temperature and adjust the pH to 7-8. Add 50 mg of solochrome black/potassium nitrate mixture [see Section 10.50(C)] and titrate rapidly with standard 0.01 M zinc sulphate solution until the colour changes from blue to wine red. 

Solutions which prevent the hydrolysis of salts of weak acids and bases. If the precipitate is a salt of weak acid and is slightly soluble it may exhibit a tendency to hydrolyse, and the soluble product of hydrolysis will be a base the wash liquid must therefore be basic. Thus Mg(NH4)P04 may hydrolyse appreciably to give the hydrogenphosphate ion HPO and hydroxide ion, and should accordingly be washed with dilute aqueous ammonia. If salts of weak bases, such as hydrated iron(III), chromium(III), or aluminium ion, are to be separated from a precipitate, e.g. silica, by washing with water, the salts may be hydrolysed and their insoluble basic salts or hydroxides may be produced together with an acid ... 

Aluminium. 25.0 mL aluminium ion solution, acidified with a few drops of 2.5M nitric add (to pH 1-2), boiled for 1 minute, 50.0 mL 0.05M EDTA added to hot solution, solution cooled, 50 mL acetate buffer and 1 drop of 0.0025 M mercury-EDTA added, excess of EDTA back-titrated with standard zinc ion solution. 

As the cement ages, absorption of water and loss of aluminium ions ceases (after 7 days). Other species - sodium and fluoride ions and silicic acid - continue to be eluted. The release of fluoride is important, for the glass polyalkenoate cement can be seen as a device for its sustained release. 

Aveston, J. (1965). The hydrolysis of the aluminium ion ultracentrifugal and acidity measurements. Journal of the Chemical Society, 4438-43. 

Komrska Satava (1970) showed that these accounts apply only to the reaction between pure zinc oxide and phosphoric acid. They found that the setting reaction was profoundly modified by the presence of aluminium ions. Crystallite formation was inhibited and the cement set to an amorphous mass. Only later (7 to 14 days) did XRD analysis reveal that the mass had crystallized directly to hopeite. Servais Cartz (1971) and Cartz, Servais Rossi (1972) confirmed the importance of aluminium. In its absence they found that the reaction produced a mass of hopeite crystallites with little mechanical strength. In its presence an amorphous matrix was formed. The amorphous matrix was stable, it did not crystallize in the bulk and hopeite crystals only grew from its surface under moist conditions. Thus, the picture grew of a surface matrix with some tendency for surface crystallization. 

Cement formation between MgO and various acid phosphates involves both acid-base and hydration reactions. The reaction products can be either crystalline or amorphous some crystalline species are shown in Table 6.5. The presence of ammonium or aluminium ions exerts a decisive influence on the course of the cement-forming reaction. 

Aluminium ions released from the dental silicate cement are also absorbed by hydroxyapatite and have a similar beneficial effect to that of fluoride (Halse Hals, 1976 Putt Kleber, 1985). Thus, the dental silicate cement confers protection against caries (dental decay) on surrounding tooth material. 

The strong interaction of polyvalent cations with polyions is well known to strongly alter the rheological properties of hydrolyzed polyacrylamide used in the tertiairy oil recovery process (1-4). The influence of divalent cations have already been studied(5-7) but the role played by the presence of small quantities of aluminium ions has never been investigated. 

Aluminium ions in AlCl3 solutions. We have performed the same type of studies by adding different amounts of copolymers and we have measured the decrease of monomeric Al ions concentration by increasing the polymer content. Figures 2 and 3 give some examples of results "Al bound" as measured by NMR is plotted as a function of pH, for two different systems and can be compared with the values calculated for K IO1 and KQ=1016. 

This result shows that is reasonable to neglect other type of interactions between aluminium ions and the polymer for instance coordination binding with amide groups,... 

Figure 2 Interactions polymer aluminium concentration of bound aluminium ions for AlCl3 (27 ppin ) and AD27 (0.25 g/1 ) Full line Calculated curve Dotted line NMR results...

Clays consist of parallel silicate layers in kaolinite, two unsymmetrical types of layers are linked by hydrogen bonds. One consists of aluminium ions and hydroxyl groups, the other of silicon and oxygen ions. Cairns-Smith does not postulate a detailed mechanism, but only describes the main thrust of his argument. Critics complain that clear experimental results are not available (however, other proponents of new hypotheses often provide no evidence to back up their suggestions ). 

Cogel method by impregnating Ti02-Si02 cogel with TEAOH solution in the presence of some amount of aluminium ions. Crystallization at 408 K while tumbling the autoclave (60 rpm). Zeolite yields —29% Si/Al — 300. Requires lesser amount of TEA+ ions than classical prehydrolysis method... 

The dissolution of aluminium is an oxidative process, so it generates several electrons. The resultant aluminium ions stay in solution next to the metal from which they came. We generate a redox couple, which we define as two redox states of the same material . 

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