Aluminium/ions/salts

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 ... 

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 ... 

Arylalkenes [23] and alkenes with electron withdrawing substituents [24] can be bis-alkylated across the alkene bond by electrochemical reaction with dflialoal-kanes giving 3- to 6-membered carbocyclic products in good yields. ITie best reaction conditions use an undivided cell with a nickel cathode and a sacrificial aluminium anode in dimethylformamide or N-methylpyrrolidone containing a tetraalkylammonium salt. Anodically generated aluminium ions are essential for the reaction. 1,2-Disubstituted alkenes, regardless of their stereochemistry, are converted to the tranj-substituted cycloalkane. 

Aluminium is tervalent in its compounds. Aluminium ions (Al3+) form colourless salts with colourless anions. Its halides, nitrate, and sulphate are water-soluble these solutions display acidic reactions owing to hydrolysis. Aluminium sulphide can be prepared in the dry state only, in aqueous solutions it hydrolyses and aluminium hydroxide, Al(OH)3, is formed. Aluminium sulphate forms double salts with sulphates of monovalent cations with attractive crystal shapes, these are called alums. 

A film became saturated with respect to aluminium ions when there was one of these in the film for every 12 stearic acid molecules, although photographs of the skim showed that appreciable adsorption could occur if the underlying solution contained only one part of aluminium in 2 X 10 parts of water Under these conditions, even if all the aluminium in the solution were concentrated in the interface, there would be only one atom of metal to every 31 molecules of stearic acid. Copper ions likewise form salts very readily, being effective from bulk concentrations as low as 1 part in 300,000,000. 

Soluble ionic compounds dissociate into their component ions when dissolved in an excess of water. The concentrations of the individual ions will depend on the amounts of these ions when the substance (salt, base or alkali) dissolves. In a 4-0 mol dm aqueous solution of aluminium nitrate, for example, the concentration of the aluminium ions is 4.0 mol dm but the concentration of the nitrate ions is 12.0 mol dm. ... 

Therefore, when an anhydrous aluminium salt is dissolved in water initially, the octahedral ion [Al(H20)j,] " is formed by hydration of the A1 ion. However, since some hydrolysis occurs, the solution will contain and be acidic. Addition of any molecule or ion... 

Salts containing the hydroxoaluminate ions [Al(OH)4(H20)2] and [Al(OH)(i] are known in solution but on heating they behave rather like aluminium hydroxide and form hydrated aluminates. 

The salt-like carbides. Among these are aluminium tricarbide imethanide) AI4C3 (containing essentially C ions) in the crystal lattice and the rather more common dicarbides containing the C ion, for example calcium dicarbide CaCjt these carbides are hydrolysed by water yielding methane and ethyne respectively ... 

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