Boron hydride has probably never been isolated in the pure condition; on heating boron trioxide with magnesium filings, a magnesium boride Mg3B2 is obtained, and if this be decomposed with dilute hydrochloric acid a very evil-smelling gas, consisting of a mixture of hydrogen and boron hydride, is obtained. This mixture burns with a green flame forming boron trioxide; whilst boron is deposited on passing the gas mixture through a hot tube, or on depressing a cold surface in the gas flame. By cooling it with liquid air Sir W. Ramsay and H. S. Hatfield obtained from it a gas of composition B3H3. The mixture probably contained also some BH3 (W. Ramsay and H. S. Hatfield, Proc. Chem. Soc., 17, p. 152). Boron fluoride BF3 was first prepared in 1808 by Gay Lussac and L. Thénard and is best obtained by heating a mixture of the trioxide and fluorspar with concentrated sulphuric acid. It is a colourless pungent gas which is exceedingly soluble in water. It fumes strongly in air, and does not attack glass. It rapidly absorbs the elements of water wherever possible, so that a strip of paper plunged into the gas is rapidly charred. It does not burn, neither does it support combustion. A saturated solution of the gas, in water, is a colourless, oily, strongly fuming liquid which after a time decomposes, with separation of metaboric acid, leaving hydrofluoboric acid HF·BF3 in solution. This acid cannot be isolated in the free condition, but many of its salts are known. Boron fluoride also combines with ammonia gas, equal volumes of the two gases giving a white crystalline solid of composition BF3·NH3; with excess of ammonia gas, colourless liquids BF3·2NH3 and BF3·3NH3 are produced, which on heating lose ammonia and are converted into the solid form.
Boron chloride BCl3 results when amorphous boron is heated in chlorine gas, or more readily, on passing a stream of chlorine over a heated mixture of boron trioxide and charcoal, the volatile product being condensed in a tube surrounded by a freezing mixture. It is a colourless fuming liquid boiling at 17–18° C, and is readily decomposed by water with formation of boric and hydrochloric acids. It unites readily with ammonia gas forming a white crystalline solid of composition 2BCl3·3NH3.
Boron bromide BBr3 can be formed by direct union of the two elements, but is best obtained by the method used for the preparation of the chloride. It is a colourless fuming liquid boiling at 90.5° C. With water and with ammonia it undergoes the same reactions as the chloride. Boron and iodine do not combine directly, but gaseous hydriodic acid reacts with amorphous boron to form the iodide, BI3, which can also be obtained by passing boron chloride and hydriodic acid through a red-hot porcelain tube. It is a white crystalline solid of melting point 43 C.; it boils at 210° C., and it can be distilled without decomposition. It is decomposed by water, and with a solution of yellow phosphorus in carbon bisulphide it gives a red powder of composition PBI2, which sublimes in vacuo at 210° C. to red crystals, and when heated in a current of hydrogen loses its iodine and leaves a residue of boron phosphide PB.
Boron nitride BN is formed when boron is burned either in air or in nitrogen, but can be obtained more readily by heating to redness in a platinum crucible a mixture of one part of anhydrous borax with two parts of dry ammonium chloride. After fusion, the melt is well washed with dilute hydrochloric acid and then with water, the nitride remaining as a white powder. It can also be prepared by heating borimide B2(NH)3; or by heating boron trioxide with a metallic cyanide. It is insoluble in water and unaffected by most reagents, but when heated in a current of steam or boiled for some time with a caustic alkali, slowly decomposes with evolution of ammonia and the formation of boron trioxide or an alkaline borate; it dissolves slowly in hydrofluoric acid.
Borimide B2(NH)3 is obtained on long heating of the compound B2S3·6NH2 in a stream of hydrogen, or ammonia gas at 115–120° C. It is a white solid which decomposes on heating into boron nitride and ammonia. Long-continued heating with water also decomposes it slowly.
Boron sulphide B2S3 can be obtained by the direct union of the two elements at a white heat or from the tri-iodide and sulphur at 440° C., but is most conveniently prepared by heating a mixture of the trioxide and carbon in a stream of carbon bisulphide vapour. It forms slightly coloured small crystals possessing a strong disagreeable smell, and is rapidly decomposed by water with the formation of boric acid and sulphuretted hydrogen. A pentasulphide B2S5 is prepared, in an impure condition, by heating a solution of sulphur in carbon bisulphide with boron iodide, and forms a white crystalline powder which decomposes under the influence of water into sulphur, sulphuretted hydrogen and boric acid.
Boron trioxide B2O3 is the only known oxide of boron; and may be prepared by heating amorphous boron in oxygen, or better, by strongly igniting boric acid. After fusion the mass solidifies to a transparent vitreous solid which dissolves readily in water to form boric acid (q.v.); it is exceedingly hygroscopic and even on standing in moist air becomes opaque through absorption of water and formation of boric acid. Its specific gravity is 1.83 (J. Dumas). It is not volatile below a white heat, and consequently, if heated with salts of more volatile acids, it expels the acid forming oxide from such salts; for example, if potassium sulphate be heated with boron trioxide, sulphur trioxide is liberated and potassium borate formed. It also possesses the power of combining with most metallic oxides at high temperatures, forming borates, which in many cases show characteristic colours. Many organic compounds of boron are known; thus, from the action of the trichloride on ethyl alcohol or on methyl alcohol, ethyl borate B(OC2H5)3 and methyl borate B(OCH3)3 are obtained. These are colourless liquids boiling at 119° C. and 72° C. respectively, and both are readily decomposed by water. By the action of zinc methyl on ethyl borate, in the requisite proportions, boron trimethyl is obtained, thus:—
2B(OC2H5)2 + 6Zn(CH3)2 = 2B(CH3)3 + 6Zn
|
CH3 |
| OC2H5 |
as a colourless spontaneously inflammable gas of unbearable smell. Boron triethyl B(C2H5)3 is obtained in the same manner, by using zinc ethyl. It is a colourless spontaneously inflammable liquid of boiling point 95° C. By the action of one molecule of ethyl borate on two molecules of zinc ethyl, the compound B(C2H5)2·OC2H5 diethylboron ethoxide is obtained as a colourless liquid boiling at 102° C. By the action of water it is converted into B(C2H5)2·OH, and this latter compound on exposure to air takes up oxygen slowly, forming the compound B·C2H5·OC2H5·OH, which, with water, gives B(C2H5)·(OH)2. From the condensation of two molecules of ethyl borate with one molecule of zinc ethyl the compound B2·C2H5·(OC2H5)5 is obtained as a colourless liquid of boiling point. 112° C. Boron triethyl and boron trimethyl both combine with ammonia.
The atomic weight of boron has been determined by estimating the water content of pure borax (J. Berzelius), also by conversion of anhydrous borax into sodium chloride (W. Ramsay and E. Aston) and from analysis of the bromide and chloride (Sainte-Claire Deville); the values obtained ranging from 10.73 to 11.04. Boron can be estimated by precipitation as potassium fluoborate, which is insoluble in a mixture of potassium acetate and alcohol. For this purpose only boric acid or its potassium salt must be present; and to ensure this, the borate can be distilled with sulphuric acid and methyl alcohol and the volatile ester absorbed in potash.
BOROUGH [Burrough, Burrowe, Borrows], STEVEN
(1525–1584), English navigator, was born at Northam in Devonshire
on the 25th of September 1525. In 1553 he took part in
the expedition which was despatched from the Thames under
Sir Hugh Willoughby to look for a northern passage to Cathay
and India, serving as master of the “Edward Bonaventure,”
on which Richard Chancellor sailed as pilot in chief. Separated
by a storm from the “Bona Esperanza” and the “Bona Confidentia,”
the other two ships of the expedition, Borough proceeded
on his voyage alone, and sailing into the White Sea, in the words
of his epitaph, “discouered Moscouia by the Northerne sea
passage to St Nicholas” (Archangel). In a second expedition,
made in the “Serchthrift” in 1556, he discovered Kara Strait,
between Novaya Zemlya and Vaygach island. In 1560 he was
in charge of another expedition to Russia, and, probably in
1558, he also made a voyage to Spain. At the beginning of 1563
he was appointed chief pilot and one of the four masters of the
queen’s ships in the Medway, and in this office he spent the rest
of his life. He died on the 12th of July 1584, and was buried at
Chatham. His son, Christopher Borough, wrote a description
of a trading expedition made in 1579–1581 from the White Sea
to the Caspian and back.
His younger brother, William Borough, born in 1536, also at Northam, served as an ordinary seaman in the “Edward Bonaventure” on her voyage to Russia in 1553, and subsequently made many voyages to St Nicholas. Later he transferred his services from the merchant adventurers to the crown. As commander of the “Lion” he accompanied Sir Francis Drake in his Cadiz expedition of 1587, but he got himself into trouble by presuming to disagree with his chief concerning the wisdom of the attack on Lagos. He died in 1599. He was the author of A Discourse of the Variation of the Compas, or Magneticall Needle (1581), and some of the charts he made are preserved at the British Museum and Hatfield.
BOROUGH (A.S. nominative burh, dative byrig, which produces
some of the place-names ending in bury, a sheltered or
fortified place, the camp of refuge of a tribe, the stronghold of a
chieftain; cf. Ger. Burg, Fr. bor, borc, bourg), the term for a
town, considered as a unit of local government.
History of the English Borough.—After the early English settlement, when Roman fortifications ceased to shelter hostile nations, their colonies and camps were used by the Anglo-Saxon invaders to form tribal strongholds; nevertheless burhs on the sites of Roman colonies show no continuity with Roman municipal organization. The resettlement of the Roman Durovernum as
