BORON (from one of the non metallic elements. In nature it is never found in the uncombined or elementary state, though it occurs abundantly in combination with other elements, especially in regions that are or have been volcanic. The principal com pounds of it that are found in nature are borax and boracic acid (qq.v.). It is a con stituent of numerous other minerals, but most of these have but little commercial importance. Boron was first obtained in the elementary state about the year 1808 by Gay-Lussac and Thenard in France and by Sir Humphry Davy in England. Gay-Lussac and Thenard pre pared the element by heating boracic acid very strongly until all its water was expelled and then heating the resulting substance (now known as boric oxid) with metallic potassium. The potassium removed the oxygen from the boric oxid, setting the element boron free. When thus prepared boron is an opaque amor phous powder of a greenish-brown color. It has neither taste nor odor, but it stains the fingers strongly. Owing to its finely divided condition it is apt to take fire spontaneously; but if it is consolidated by pressure it is not affected by the air at common temperatures, though it burns with a reddish light when heated. It is not affected by water save that water will dissolve a slight amount of it when it is freshly prepared. Strong nitric acid will dissolve it in the cold and hot sulphuric acid attacks it also. It is one of the few sub stances that will combine directly with nitro gen, which it does when heated in that gas. The atomic weight of boron has not been de termined with satisfactory precision, but Clarke gives 10.97 as the best result obtainable from the existing data. The amorphous boron described above is soluble in melted aluminum, from which it crystallizes out on cooling.
The crystals so obtained were formerly thought to consist of pure boron, but it has been shown that they always contain a definite amount of aluminum. These crystals may be obtained of such hardness that they will scratch both corundum and the ruby, the dia mond being the only substance that exceeds them in this respect. The specific gravity of amorphous boron has not been satisfactorily determined, but it appears to exceed 1.84. The specific gravity of the crystals obtained as described above is said by Miller to be 2.68. The specific heat of boron varies con siderably with the temperature. At 250° C. it is .37 and at 1,000° C. it is probably 0.5. Boron is a non-conductor of electricity.
BORORoS, b6-ro-r&e, a tribe of South American Indians of the Tupi or Guarani stock, variously reported from a few hundred to a thousand, living in southwestern Brazil around the headwaters of the Parana and Paraguay, the small remnants of a once pow erful race, thinned by old Portuguese slave raids and disease. They live in villages and do some planting, but live mainly by hunting with long bows and bone-tipped arrows. They are exceptionally tall, averaging over five feet eight inches, and athletic, and are reported to practice both polygamy and polyandry, but little is fealty known of them. Their language is of the Otuquian family. Consult Pric and Radin, in the Journal of the Royal Anthro pological Institute (1906); Chamberlain, in the American Anthropologist (1912); also 'I Bororos-Coroadosdel Matto) by the Salesian missionaries (Turin 1906); Cook, in 'Mis cellaneous Collections> (of the Smithsonian Institute, Vol. V, p. 50, Washington 1907).