Beryllium aluminate

A gem closely related to ruby and emerald is alexandrite, named after Alexander II of Russia. This gem is based on the mineral chrysoberyl, a beryllium aluminate with the empirical formula BeO AI2O3 in which approximately 1% of the Al3+ ions are replaced by Cr3+ ions. In the chrysoberyl environment Cr3+ absorbs strongly in the yellow region of the spectrum. Alexandrite has the interesting property of changing colors depend-... 

Beryllium Aluminate, Be(A10j)o.—Occurs in nature as chryso-beryl (cymophane, alexandrite) and prepared artificially by Ebel-men (1851 3) by fusing theoretical portions of alumina and beryllia in boric anhydrid and later, by Hautefeuille and Perrey by fusing a mixture of the oxides of aluminum and beryllium in leucite or nephelite. 

Beryllium has the highest heat of combustion of the solid elements, followed by boron and aluminium. Aluminium is a relatively cheap and useful element, and is used to increase the performance of explosive compositions, such as aluminized ammonium nitrate and aluminized... 

Beryllium reacts readily with sulfuric, hydrochloric, and hydrofluoric acids. Dilute nitric acid attacks the metal slowly, whereas concentrated nitric acid has litde effect. Hot concentrated alkalies give hydrogen and the amphoteric beryllium hydroxide [13327-32-7], Be(OH)2. Unlike the aluminates, the beryllates are hydrolyzed at the boil. 

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The product in this case is sodium aluminate, a compound that contains the aluminate ion, [Al(OH)4]. Because aluminum oxide reacts with both acids and bases, it is classified as amphoteric. Other main-group elements that form amphoteric oxides are shown in Fig. J.3. As you can see, these elements lie in a diagonal band across the table from beryllium to polonium. The acidic, amphoteric, or basic character of the oxides of the d-block metals depends on their oxidation state (see Chapter 16). 

Another method for separating beryllium and aluminium consists of adding excess of a solution of sodium fluoride to the solution. The complex hexafluoro-aluminate, [A1F6]3 , is formed from which the metal is not precipitated as hydroxide by ammonia solution. Beryllium is, however, readily precipitated as the hydroxide under these conditions. 

Beryllium is an understandable exception, but then its salts are more covalentHowever, by the use of less stable salts such as alkoxides, R3AI can produce aluminates with these metals (equation 53). ... 

Sodium Xylene Sulfonate Xylidine Copper Gluconate Sodium Aluminate Calibre 302-6 Arsenic Trisulfide Boric Oxide Boron Trioxide Barium Oxide Barium Peroxide Beryllium Oxide Bismuth Subnitrate Calcium Hydroxide Lime Water Calcium Oxide Calcium Peroxide Cadmium Oxide Cadmium Sulfide Chromic Hydroxide Chromic Oxide Ferric Hydroxide Rouge... 

Pour the acidified solution into a beaker with approx. 50 ml of cold 4 m sodium hydroxide solution. Beryllium and aluminium remain in solution as beryllate and aluminate respectively, while iron, titanium and manganese are precipitated. Leave to stand for several hours, filter, collect the... 

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