Q. Illustrate important catalyst of aluminium?
Anhydrous AlCl3 is an important catalyst, used in organic synthesis and in the cracking of petroleum. Al2(S04)3 as such or as potash alum, K2S04.Al2(S04)3.24H20 is used for sizing paper, for tanning leather, for waterproofing cloth and as a mordant for dying cotton. It is extensively used for purification of water and in sewage treatment.
Because of its extreme hardness, high m.p., non-volatility, chemical inertness and good electrical insulating properties, corundum (Al203,) finds many applications in abrasives, refractories and ceramics. Large crystals of a-Al203 when coloured with metal-ion impurities are prized as gemstones, e.g., ruby (cr3+, red), sapphire (Fe2+3+Ti4+ , blue), oriental emerald (cr3+/V3+, green), oriental topaz (Fe3+, yellow), etc. Aluminates are important constituents of Portland cement. Gallium has the longest liquid range (303-2343 K) of any known substance and so finds use as a high temperature thermometer liquid.