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Home >> Chemistry Dictionary >>Aluminium Silicates - Alums
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Aluminium ethanoate (aluminium acetate).
A white solid, Al(OOCCH2)3. which decomposes on heating, is very slightly soluble in cold water, and decomposes in warn water.
(CH3CH2O)3Al. M.p. 1390C, b.p. 3200C
Aluminium fluoride (AlF3).
A colurless substance obtained by the action of HF on Al(OH)3. An inert material, relatively insoluble in most solvents unattacked by acid and alkali.
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Aluminum hydride,
AlH3. A white polymeric substance (H2SO4 plus LiAlH4 in ThF). A useful reducing agent (e.g. RCN gives RCH2NH2); reacts with alcohols to give alkoxy hydrides, including the important tetrahedral tetrahydro-aluminate ion, [AlH4], LiAlH40 (LiH plus AlCl3 in ether) is a very important reducing agent e.g. RCOOH gives RCH2OH) and starting point for the formation of Al derivatives, e.g. RNH2 gives Li[Al(NHR)4]. Alkoxy derivatives, e.g. Li[AlH(OR)3] and Na[AlH(OMe)2(OEt) are good and often specific reducing agents.
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Aluminium hydroxide, Al(OH)3.
A white gelatinous solid is obtained when added with ammonia to the solution of aluminium salts as the precipitate is amorphous and dries to a glassy solid. It is used to prepare water proof cloth and as a mordant.
Aluminium iodide.
Al3. Very similar to AlCl3 formed from Al and l2.
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Aluminium nitrate.
[Al(NO3)2]. A white solid obtained by adding freshly precipitated aluminium hydroxide in dilute nitric acid, or by mixing solution of aluminium sulphate and lead nitrate and filtering off the lead sulphate. It is used as mordant for dyeing and preparing gas mantles.
Aluminum oxide (Al2O3).
A white amorphous solid occurs in the nature as Corundum or emery which is coloured black by iron oxide Fe2O3. In the hydrated form, it mainly exists as bauxite Al2O3 2H2O Alumina is largely used as refractory for lining of furnaces and for making refractory bricks. Artificial gems are prepared by fusing alumina with small quantities of the colouring oxides life, Cr2O3, Fe2O3 etc. in electric furnace.
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Aluminium silicates.
A large class of minerals, both natural and synthetic, having aluminium and silicon combined with oxygen in their structure. It includes clays, zeolites, micas and amny other important minerals.
Aluminium sulphate.
[Al2(SO4)3]. Anhydrous aluminium sulphate is white powder. It is fairly soluble in water, giving an acidic solution because of hydrolysis. It is used to manufacture alums, as a refill in foam type fire-extinguishers, tanning of leather, as mordant for dyeing and a mixture of sodium bicarbonate and aluminium sulphate is used as baking powder.
Aluminium sulphate is commercially one of the most important aluminium compounds; it is used in sewage treatment (as a flocculating agent) and in the purification of drinking water, the paper industry, and in the preparation of mordants. It is also a fire-proofing agent Aluminium sulphate is often wrongly called alum in these industries.
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Aluminous cement.
A hydraulic cement closely resembling Portland cement, but composed chiefly of calcium aluminate.
Alundum.
An artificial form of Corundum (Al2O3) made by fusing calcined bauxite in an electric furnace. It is used for highly refractory bricks, crucibles and muffles.
Alums.
A group of crystalline double sulphate of general formula MiMiii (SO4)2, 12H2O. The sulphate group may be replaced by SeO42-, BeF42-or ZnCl42-. The crystals are made up of [Mi(H2O)6]+ and [Miii(H2O6]3+ cations and SO4M2- anions (three different structures are known) and in solution the alums behave chemically as mixtures of the two contitutent sulphates. KAl(SO4)2, 12H2O is normally known as potash alum and the sodium and ammonium. Theses latter derivative are prepared in the same manner as potash alum.
Amaranth.
An important red azo dye used in foodstuffs.
Amatol.
A mixture of NH4NO3 and TNT used as an explosive.
Amber.
A fossil resign of a pine o the Tertiary period, an amorphous substance.
Ambident anions.
Anions which are capable of reaction at two or more different sites, e.g., NO2 (from AgNO2) can react with RX to give nitrites RONO and nitroalkanes, RNO2
Ambident ligands.
Ligands which can use more than one co-ordinating site. e.g., NH2CH2COOH can co-ordinate through N or O.
Amblygonite.
Lia 1 (F, OH) PO4. A lithium ore
Amethyst.
The term used for the purple variety of the mineral quartz. The colour is due to impurities, especially iron oxide. It finds use as a gemstone.
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