Various minerals are employed in the manufacture of alum, the most important being alunite or alum-stone, alum schist, bauxite and cryolite.
In the preparation of alum from clays or from bauxite, the material is gently calcined, then mixed with sulphuric acid and heated gradually to boiling; it is allowed to stand for some time, the clear solution drawn off and mixed with acid potassium sulphate and allowed to crystallize.
Bauxite, probably derived from the decay of lavas, is found between Glenarm and Broughshane, associated with brown and red pisolitic iron-ores; both these materials are worked commercially.
Bauxite occurs also near Ballintoy.
Bauxite was produced on a commercial scale in four states in 1908: Alabama, Arkansas, Georgia and Tennessee; Arkansas pro- Other ducingas for years pastmore than six-tenths of the total product of the country.
Gold, silver, lead, copper, tin and bauxite have also been discovered, but the greater richness of the iron and coal deposits has prevented their development.
Bauxite is a hydrated oxide of aluminium of the ideal composition, Al 2 0 3.2H 2 0.
After being dried at loo° C., Antrim bauxite contains from 33 to 60% of alumina, from 2 to 30% of ferric oxide, and from 7 to 24% of silica, the balance being titanic acid and water of combination.
Therefore while less energy is absorbed in its final reduction, more is needed in its initial preparation, and it is questionable whether the economy possible in the second stage would not be neutralized by the greater cost of the first stage in the whole operation of winning the metal from bauxite with the sulphide as the intermediary.
In order to prepare pure alumina, bauxite and sodium carbonate were heated in a furnace until the reaction was complete; the product was then extracted with water to dissolve the sodium aluminate, the solution treated with carbon dioxide, and the precipitate removed and dried.
The original Deville process for obtaining pure alumina from bauxite was greatly simplified in 1889 by K.
The filtrate, now containing roughly two molecules of alumina to one of soda, is concentrated to the original gravity of 1.45, and employed instead of fresh caustic for the attack of more bauxite; the precipitate is then collected, washed till free from soda, dried and ignited at about looo C. to convert it into a crystalline oxide which is less hygroscopic than the former amorphous variety.
In 1895 the British Aluminium Company was founded to mine bauxite and manufacture alumina in Ireland, to prepare the necessary electrodes at Greenock, to reduce the aluminium by the aid of water-power at the Falls of Foyers, and to refine and work up the metal into marketable shapes at the old Milton factory of the Cowles Syndicate, remodelled to suit modern requirements.
Of these hydrargillite or gibbsite, Al(OH)3, diaspore, A10(OH), and bauxite, Al 2 0(OH) 4, occur in the mineral kingdom.
Bauxite was discovered in the state in 1887, and the product increased from 5045 long tons in 1899 to 50,267 long tons in 1906, the production for the whole country in 1899 being 35,280 long tons and in 1906 7 5,33 2 long tons.
The only other states in which bauxite was produced during the period were Alabama and Georgia, which in this respect have greatly declined in importance relatively to Arkansas.
There is some roofing slate along the Rogue river, natural cement, nickel ore, bismuth and wolframite in Douglas county, gypsum in Baker county, fire-clay in Clatsop county, borate of soda on the marsh lands of Harney county, infusorial earth and tripoli in the valley of the Deschutes river, chromate of iron in Curry and Douglas counties, molybdenite in Union county, bauxite in Clackamas county, borate of lime in Curry county, manganese ore in Columbia county, and asbestos in several of the southern and eastern counties.
Alum clay or bauxite, from which aluminium is manufactured, is found in the same county.
Rome is situated in a rich agricultural region producing cotton, cereals, vegetables and fruits, for which it is a trading centre, and is a shipping point for bauxite, mined in the vicinity.