NOTES

Propertiesof Aluminium (i)         It is a silvery metal with a density of 2.7 g/cc, having a melting point of 660 o C, and is a good conductor of heat and electricity. It is malleable and ductile. (ii)        Action of air : Dry air has no action on aluminium. But moist air forms a thin layer of Al 2 O 3   on its surface and it loses its luster. At very high temperatures it burns to form Al 2 O 3   and AlN. (iii)       Reaction with halogens : When gaseous halogens are passed over aluminium, its halide are formed in an anhydrous form. 2Al + 3Cl 2   2AlCl 3 (iv)       Action of alkalies: When warmed with concentrated NaOH, it liberates H 2   gas and a colourless solution of sodium meta-aluminate is formed.            ...

Preparation             Borax occurs naturally as tincal(contains about 55% borax) in certain inland lakes of India, Tibet andCalifornia (U.S.A.).             Borax can also be prepared from certain other minerals such as boracite, colemanite and boranatrocalcite. The minerals are powdered and boiled with sodium carbonate solution.                      Ca 2 B 6 O 11   +   2Na 2 CO 3 ¾ ®     2CaCO 3   +   Na 2 B 4 O 7   +   2NaBO 2             Borax is crystallised from the filtrate. Sodium metaborate, present in the mother liquor, is converted into borax by passing carbon dioxide through it            ...