Is sodium aluminum sulfate basic or acidic

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Other aluminum connections

Aluminum salts

When acids are added to aluminum hydroxide, oxide hydroxide or oxide, aluminum salts are formed with the water-containing cation. However, this is only stable in water at pH <3; above this, deprotonation takes place and, with elimination of water, dinuclear and polynuclear cation complexes are formed.

Aluminum sulfate

Aluminum sulfate,, is the most frequently used aluminum compound after oxide. It can be obtained technically by digesting bauxite or kaolin with 70% sulfuric acid, but the removal of the iron contained as an impurity requires considerable effort. It is easier to manufacture by dissolving pure aluminum hydroxide,, in concentrated sulfuric acid at 100:

The water-containing sulfate forms colorless, needle-shaped crystals. In the lattice there are and ions as well as water of hydration. The salt is readily soluble in water. The aqueous solution reacts acidic as a result of partial hydrolysis reversing the equilibrium (X). When the sulphate is heated, complete dehydration to the anhydrous, white, powdery form takes place via intermediate stages above 340 with lower hydrate levels.

Most of the aluminum sulphate produced in the megaton range is used in the paper industry to glue paper. Other areas of application are the use as tanning and pickling agents in the textile industry, in water treatment as a flocculant and as a starting material for the preparation of other aluminum compounds.


With sulfates of monovalent metal cations MI.2SO4 (=,,,, and) combine to form double salts of the composition M.I.So4)2 ยท 12 H.2Oh, the so-called alums.

Among the alums, the greatest technical importance is found in naturally occurring potash alum, which is used in the same areas as pure aluminum sulphate. The representation takes place via the digestion of bauxite or clay with 70% sulfuric acid, whereby the alum crystallizes out of the solution after the addition of.

Aluminum diacetate

The basic aluminum diacetate, which is used as acetic acid clay in the pharmaceutical-cosmetic field because of its antiseptic and astringent, i.e. bleeding-stopping effect, is obtained, for example, by reacting sodium aluminate with acetic acid:


Aluminosilicates are compounds in which the silicon from the silicate basic structure is partially substituted by aluminum. Like the silicon atoms, the aluminum atoms are also firmly integrated into the grid and connected to the oxygen atoms by covalent bonds. The linking of - and - tetrahedra is characteristic of the structure of many aluminosilicates. Since the aluminum ion has one less positive charge than the -ion, additional cations, such as,,,, are required to neutralize the anionic structure. These are bound by ionic relationships, but do not occupy a fixed position in the spatial grid and are freely movable in the channels and cavities of the structure, as are existing water molecules. The cations can thus be easily exchanged without changing the basic structure of the crystal lattice.

Alumosilicates are widespread in nature as feldspars, mica (Fig. 1) and natural zeolites. Many of the minerals, especially soda, potash and lime feldspar, as well as their weathering products (clays such as kaolinite, (Fig. 2)) are used as raw materials in glass and ceramic production (e.g. for boron-alumina glasses, earthenware, Porcelain), also used as fillers for paints, varnishes and plastics.

The tourmalines, known as gemstones, are natural aluminoborosilicates, in whose framework structure there is also boron in addition to aluminum.

In contrast, the zeolites used in laboratories and technology are predominantly synthetically produced materials. They are mainly used as ion exchangers, adsorbents, catalysts or as their carriers.

The use of zeolites for ion exchange is based on the easy exchangeability of the bound cations for other ions, so that water can be softened using zeolite (exchange of calcium ions in water for sodium ions). The zeolite material used for the exchange (zeolite A, permutite) can be regenerated by treatment with solution. The use of zeolites in detergents made it possible to significantly reduce the proportion of ecologically harmful phosphates.

Zeolites that are dried at high temperatures, i.e. water-free, act as desiccants for gases, solvents, etc., as they can store water again in the existing cavities. They also act as adsorbents for other small molecules such as or. Depending on the nature of the channels, zeolites are also suitable for separation processes, whereby molecules of the appropriate size penetrate the cavities and are adsorbed by electrostatic or van der Waals forces, but larger or bulky molecules are not and even smaller particles enter the cavity again can leave (molecular sieve effect). Zeolites therefore serve as so-called Molecular sieves (Molecular sieves) when separating mixtures of substances (e.g. separation of straight-chain and branched or aromatic hydrocarbons, see catalysts). This property of the zeolites is used both on an industrial scale and in the laboratory, e.g. in chromatographic-analytical processes.

Aluminum-organic compounds

Among the organic compounds of aluminum, the triorganyl compounds,, are of particular importance as reducing and organizing agents. The role of triethylaluminum, in combination with transition metal compounds such as titanium (IV) chloride, as a catalyst for the polymerization of olefins (Ziegler-Natta catalyst, Ziegler-Natta polymerization, Nobel Prize in Chemistry 1963) should be emphasized.

Triethyl aluminum

Detailed description of structure, properties, synthesis, reactivity and use in the learning unit Triethylaluminium