BORON (symbol B, atomic weight ii), one of the non-metallic elements, occurring in nature in the form of boracic (boric) acid, and in various borates such as borax, tincal,.
Thenard in 1808 by heating boron trioxide with potassium, in an iron tube.
After the vigorous reaction has ceased and all the sodium has been used up, the mass is thrown into dilute hydrochloric acid, when the soluble sodium salts go into solution, and the insoluble boron remains as a brown powder, which may by filtered off and dried.
Pure amorphous boron is a chestnut-coloured powder of specific gravity 2.45; it sublimes in the electric arc, is totally unaffected by air at ordinary temperatures, and burns on strong ignition with production of the oxide B 2 0 3 and the nitride BN.
By strongly heating a mixture of boron trioxide and aluminium, protected from the air by a layer of charcoal, F.
Sainte-Claire Deville obtained a grey product, from which, on dissolving out the aluminium with sodium hydroxide, they obtained a crystalline product, which they thought to be a modification of boron, but which was shown later to be a mixture of aluminium borides with more or less carbon.
Boron dissolves in molten aluminium, and on cooling, transparent, almost colourless crystals are obtained, possessing a lustre, hardness and refractivity near that of the diamond.
Boron hydride has probably never been isolated in the pure condition; on heating boron trioxide with magnesium filings, a magnesium boride Mg 3 B 2 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.
Boron fluoride BF 3 was first prepared in 1808 by Gay Lussac and L.
Boron fluoride also combines with ammonia gas, equal volumes of the two gases giving a white crystalline solid of composition BF 3 NH 3 i with excess of ammonia gas, colourless liquids BF 3.2NH 3 and BF 3.3NH 3 are produced, which on heating lose ammonia and are converted into the solid form.
Boron chloride BC1 3 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.
Boron bromide BBr 3 can be formed by direct union of the two elements, but is best obtained by the method used for the preparation of the chloride.
Boron and iodine do not combine directly, but gaseous hydriodic acid reacts with amorphous boron to form the iodide, BI 31 which can also be obtained by passing boron chloride and hydriodic acid through a red-hot porcelain tube.
It is decomposed by water, and with a solution of yellow phosphorus in carbon bisulphide it gives a red powder of composition PBI 2, 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.
It can also be prepared by heating borimide B2(NH)31 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 B 2 (NH) 3 is obtained on long heating of the compound B 2 S 3.6NH 3 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.
Boron sulphide B 2 S 3 can be obtained by the direct union of the two elements at a white heat or from the tri-iodide and sulphur at 44 0 ° C., but is most conveniently prepared by heating a mixture of the trioxide and carbon in a stream of carbon bisulphide vapour.
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.
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.
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(OCH 3) 3 are obtained.
By the action of zinc methyl on ethyl borate, in the requisite proportions, boron trimethyl is obtained, thus :-2B(OC2H5)2+ 6Zn(CH 3) 2 =2B(CH 3) 3 +6Zn< OC2H5 as a colourless spontaneously inflammable gas of unbearable smell.
Boron triethyl B(C 2 H 5) 3 is obtained in the same manner, by using zinc ethyl.
(0C2H5)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.
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.
Chem., 1848, 44, P. 301), or by long fusion of a mixture of ammonium molybdate, potassium carbonate, and boron trioxide (W.
Carbon was joined with silicon, zirconium and titanium, while boron, being trivalent, was relegated to another group. A general classification of elements, however, was not realized by Frankland, nor even by Odling, who had also investigated the question from the valency standpoint.
Thus, hydrogen unites with but a single atom of chlorine, zinc with two, boron with three, silicon with four, phosphorus with five and tungsten with six.
The discovery of boron by Gay Lussac and Davy in 1809 led Berzelius to investigate silica (silex).
The preparation of crystalline boron in 1856 by Wohler and Sainte Claire Deville showed that this element also existed in allotropic forms, amorphous boron having been obtained simultaneously and independently in 1809 by Gay Lussac and Davy.
The results of Berzelius were greatly extended by Hermann Kopp, who recognized that carbon, boron and silicon were exceptions to the law.
The specific heats of carbon, boron and silicon subsequently formed the subject of elaborate investigations by H.
Weber, who showed that with rise of temperature the specific (and atomic) heat increases, finally attaining a fairly constant value; diamond, graphite and the various amorphous forms of carbon having the value about 5.6 at moo°, and silicon 5.68 at 232°; while he concluded that boron attained a constant value of 5.5.
Mehner patented heating the oxides of silicon, boron or magnesium with coal or coke in an electric furnace, and then passing in nitrogen, which forms, with the metal liberated by the action of the carbon, a readily decomposable nitride.
By fusing litharge with boron trioxide, glasses of a composition varying with the proportions of the mixture are obtained; some of these are used in the manufacture of glass.
The metals used in different combinations included tin, aluminium, arsenic, antimony, bismuth and boron; each of these, when united in certain proportions with manganese, together with a larger quantity of copper (which appears to serve merely as a menstruum), constituted a magnetizable alloy.
In 1858 he pointed out the isomorphism of the fluostannates and the fluosilicates, thus settling the then vexed question of the composition of silicic acid; and subsequently he studied the fluosalts of zirconium, boron, tungsten, &c., and prepared silicotungstic acid, one of the first examples of the complex inorganic acids.
By heating crystallized silicon with boron in the electric furnace H.
The isolation of metallic titanium is very difficult since it readily combines with nitrogen (thus resembling boron and magnesium) and carbon.
Tantalum pentoxide, Ta205, is a white amorphous infusible powder, or it may be crystallized by strongly heating, or by fusing with boron trioxide or microcosmic salt.
Sodium is largely employed in the manufacture of cyanides and in reduction processes leading to the isolation of such elements as magnesium, silicon, boron, aluminium (formerly), &c.; it also finds application in organic chemistry.
In composition it approximates to Cr203 H20, but it always contains more or less boron trioxide.
Robert de Boron (c. 1215) took the subject of his Merlin (published by G.
At high temperatures it acts as a reducing agent, reducing silica to silicon, boric acid to boron, &c. (H.
BORIC ACID, or Boracic Acid, H 3 B0 3, an acid obtained by dissolving boron trioxide in water.
The acid on being heated to Ioo° C. loses water and is converted into metaboric acid, HBO 3 i at 140° C., pyroboric acid, H 2 B 4 0 7, is produced; at still higher temperatures, boron trioxide is formed.
Conspicuous examples are afforded by oxygen, carbon, boron, silicon, phosphorus, mercuric oxide and iodide.