<P> Aluminium is usually alloyed--it is used as pure metal only when corrosion resistance and / or workability is more important than strength or hardness . The strength of aluminium alloys is abruptly increased with small additions of scandium, zirconium, or hafnium . A thin layer of aluminium can be deposited onto a flat surface by physical vapor deposition or (very infrequently) chemical vapor deposition or other chemical means to form optical coatings and mirrors . </P> <P> Because aluminium is abundant and most of its derivatives exhibit low toxicity, the compounds of aluminium enjoy wide and sometimes large - scale applications . </P> <P> Aluminium oxide (Al O) and the associated oxy - hydroxides and trihydroxides are produced or extracted from minerals on a large scale . The great majority of this material is converted to metallic aluminium . In 2013, about 10% of the domestic shipments in the United States were used for other applications . One major use is to absorb water where it is viewed as a contaminant or impurity . Alumina is used to remove water from hydrocarbons in preparation for subsequent processes that would be poisoned by moisture . </P> <P> Aluminium oxides are common catalysts for industrial processes; e.g. the Claus process to convert hydrogen sulfide to sulfur in refineries and to alkylate amines . Many industrial catalysts are "supported" by alumina, meaning that the expensive catalyst material (e.g., platinum) is dispersed over a surface of the inert alumina . </P>

The correct formula for a compound formed from the element al and o is
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