Aluminium salts

Aluminium phosphates, singly or as mixture components, have many uses which include the following  

A1P04 White pigments, corrosion inhibitors, dental cements, building blocks 

A1(H2P04)3 Dental cements, metal coatings, glaze compositions, refractory binders 

A1(H2P04)(HP04) Cement and refractory binders, adhesives 

NaAl3H (P04)8 THjO Leavening (baking) (approximate composition) 

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C]2Hi50]2. Colourless needles m.pr. 286-288°C. When heated it decomposes into pyro mellitic anhydride, water and CO2. Occurs as the aluminium salt (honeystone) in some lignite beds. Prepared by oxidation of charcoal with concentrated nitric acid. 

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 ) ... 

A white gelatinous precipitate of aluminium hydroxide is obtained when an alkali is added to an aqueous solution of an aluminium salt. Addition of an excess of caustic alkali causes the precipitate to redissolve, the whole process being reversed by the addition of a strong acid the actual substance present at any time depending on... 

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... 

On standing, gelatinous aluminium hydroxide, which may initially have even more water occluded than indicated above, is converted into a form insoluble in both acids and alkalis, which is probably a hydrated form of the oxide AI2O3. Both forms, however, have strong adsorptive power and will adsorb dyes, a property long used by the textile trade to dye rayon. The cloth is first impregnated with an aluminium salt (for example sulphate or acetate) when addition of a little alkali, such as sodium carbonate, causes aluminium hydroxide to deposit in the pores of the material. The presence of this aluminium hydroxide in the cloth helps the dye to bite by ad sorbing it—hence the name mordant (Latin mordere = to bite) dye process. 

Addition of ammonium hydroxide to a solution of an aluminium salt gives a white gelatinous precipitate of aluminium hydroxide, Al(OH)3, insoluble in excess. Sodium hydroxide gives the same precipitate, but in this case, it does dissolve in excess. 

Addition of ammonium hydroxide to an aluminium salt in solution in presence of alizarin, gives a pink precipitate. 

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 ... 

The addition of an acid to the wash solution will prevent the hydrolysis of iron(III) or similar salts thus dilute hydrochloric acid will serve to remove iron(III) and aluminium salts from precipitates that are insoluble in this acid. 

Mendeleev predicted that salts of germanium are less stable than those of aluminium. In fact aluminium salts are the more readily hydrolysed. 

Indium sulphate is slightly more stable than the aluminium salt and decomposition curves (1073—1273 K) fitted [777] the Avrami—Erofe ev equation [eqn. (6)] with values of n increasing with temperature from 1.0 to 1.6. Gallium sulphate is less stable and decomposes between 833 and 973 K[770]. 

Akitt, J. W., Greenwood, N. N. Lester, G. D. (1971). Nuclear magnetic resonance and Raman studies of aluminium complexes formed in aqueous solutions of aluminium salts containing phosphoric acid and fluoride ions. Journal of the Chemical Society, A, 2450-7. 

Magnesium (or magnesia) phosphate cements are based on the reaction between ignited magnesium oxide and acid phosphates, which are generally modified by the addition of ammonium and aluminium salts. The phosphates may be either in solution or blended in solid form with the magnesium oxide. In the latter form the cement is formed by mixing the powder blend with water. 

Trinitrophenol can only be stored safely in the form of a paste with water. Lead, mercury, copper, zinc, iron and nickel salts are sensitive to impact, friction and heat. Sodium, ammonium and amine salts give rise to explosions. When it was poured on to a cement floor, trinitrophenol formed a calcium salt that detonated when it came into contact with shoes. Trinitrophenol salts in the form of moist paste are stable. Aluminium salt is not explosive, but combusts spontaneously when in contact with water. 

Fatty acids, their glycerides and other esters, including fats, waxes and oils such as mineral and vegetable oils fatty alkylamines and acylamides. Alkaline earth metal or aluminium salts of fatty acids tend to leave deposits on machinery [536]. 

Certain limitations of organic defoamers can be minimised by judicious formulation of mixtures. The following system is said to overcome some of the drawbacks associated with aluminium salts of fatty acids [536] ... 

In the beginning of the eighties, the clinical application of DFO expanded to a new type of patient, namely those on maintenance dialysis. As we will see in Chapter 12, some patients suffered from aluminium overload, mostly due to the use of aluminium salts as phosphate binders, while others had obvious transfusional iron overload in the pre-erythropoietin era. DFO was therefore used either to remove aluminium, excess iron or both. Nephrologists established that DFO therapy did not increase the overall incidence of bacterial infections but that it slightly increased the risk of bacteraemia caused by Y. enterocolitica or Y. pseudotuberculosis, as had been previously observed in thalassaemic patients (Boelaert et ah, 1987 Tielemans et ah,... 

In this case, the aluminium salt of the hydroxy acid is soluble in the reaction medium. It precipitates on addition of a number of solvents such as alcohols or ethers. 90% product-selectivity was observed in preparative syntheses (up to 40 g of pure 2-(6-methoxynaphthyl)propionic acid per run). The power consumption was given as about 2.7 kWhkg-1. 

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