Element Beryllium, Be, Alkaline Earth Metal
|Beryllium occupies the same position among the alkaline earth metals as lithium does among the alkali metals. Its combining weight is the smallest, and its similarity to the other elements of the group is least. Its properties exhibit a distinct tendency towards the next group, that of the earth metals. The combining weight of beryllium amounts to 9.1. |
Metallic beryllium can be prepared by electrolysis, by the reduction of the oxide with magnesium, of the chloride with sodium, and in other ways. It is a white metal, which is still more stable to moist air than magnesium, and decomposes water only slowly even when heated. It is readily dissolved by dilute acids, with evolution of hydrogen, and passes thereby into the ionic state.
Besides the typical divalent ion Be••, beryllium also forms other ions containing oxygen; these will be discussed later. Of the metals hitherto considered, it is the first that is capable of forming different ions.
Beryllion, Be••, is colourless and is distinguished by a conspicuously sweet taste. This fact procured for the element the passing name of glucinum (still occasionally used in France and England); the name beryllium is derived from that of its most important naturally occurring compound, beryl, which is a silicate containing aluminium.
Beryllion forms various salts, of which the chloride, BeCl2. and the sulphate, BeSO4, are the best known. They are both soluble in water, and the solutions react acid. This is due to incipient hydrolysis, since beryllium hydroxide is a weak base.
Beryllium hydroxide, Be(OH)2, is obtained as a white, gelatinous precipitate on bringing beryllion and hydroxidion together; it is not measurably soluble in water, and has no basic reaction. It dissolves in acids, with formation of beryllium salts, and on being heated is converted into a white powder of beryllium oxide.
Beryllium hydroxide dissolves in caustic potash or caustic soda. Since these bases, by reason of their containing hydroxyl, should, in accordance with well-known principles, diminish the solubility of beryllium hydroxide, this contradiction requires an explanation. This is yielded by the fact that the compound BeO2H2 can split off hydrion and behave like a very weak acid. Accordingly, it gives the two ions HBeO2'' and BeO2'' (just as carbonic acid gives the ions HCO3' and CO3''), and it is these and not beryllion, Be••, that are present in the solution in question. The compound is also obtained by fusing beryllium hydroxide with caustic soda and dissolving the melt in water.
If this alkaline solution is allowed to stand a long time, or if it is heated to boiling, almost all the beryllium hydroxide is precipitated. The question now arises why the chemical equilibrium, which had previously existed, is now disturbed, since no new substance has been added. The answer is to the effect that the beryllium hydroxide which is precipitated is a different, and indeed a more stable and less soluble, form of the hydroxide than the freshly precipitated form which is soluble in alkalis. In other words, the newly prepared solution is supersaturated with respect to the more stable form of the hydroxide, and therefore cannot continue to exist when the latter form is present. Since this form is not present in the newly prepared solution, the precipitation can commence only after the first traces of it have been formed. At the ordinary temperature this occurs slowly, but quickly when heated.
|There have been two hesitancies over beryllium - a minor hesitancy over its name and a major hesitancy over its valency. It is still called both " beryllium " and "glucinum," but the name "beryllium " is adopted in this series. Beryllium is now almost universally regarded as divalent, though there may be a few compounds in which its valency is higher. |
Vauquelin discovered la terre du beril in 1797. Hauy had emphasised the close resemblance between beryl and the emerald; Vauquelin examined the two minerals carefully and proved their chemical identity - confirming an opinion mentioned by Pliny. Klap- roth had found in them silica, alumina, and ferric oxide; their present constitution, double silicates of beryllium and aluminium, 3BeO.Al2O3.6SiO2, is the result of Vauquelin's discovery that the alumina was accompanied by beryllia. He discovered the new oxide by its deposition from a boiling solution of potassium hydroxide, and distinguished it from alumina mainly by its solubility in ammonium carbonate, his failure to obtain potash alum from it, its higher basicity, its complete precipitation by ammonia, and by the sweetness of its salts, as well as by a number of other differences. Subsequent research has fully confirmed his discovery.
A tendency soon developed to call the new earth "glucine," because its salts were sweet, and Vauquelin's own name for it, derived from its source, was superseded in France by the newer term. "Beryllerde " was, however, preferred in Germany, because sweet salts were not peculiar to the new earth. The names " glucinum " and " beryllium " were subsequently adapted from the original terms to denote the metal itself, and both are still in use.
Thirty years after Vauquelin's isolation of beryllia, Bussy and Wohler, working independently, isolated the metal itself by reducing the chloride with metallic potassium.
Towards the end of the nineteenth century electrolytic methods for isolating beryllium were discovered, and the metal is now usually prepared by electrolysing its compounds in the presence of a fluoride. In 1916 it was obtained of 99.5 per cent, purity.
Since beryllium is intimately associated with aluminium in nature and resembles it in many ways, it was natural to assume its trivalency, but, after a long controversy, the determination of the vapour density of its chloride by Nilson and Pettersson, in 1884 and 1886, indicated that it was divalent, like magnesium. Humpidge confirmed this result in 1885, and drew the same conclusion from his determination of the vapour density of the bromide. The run of the data in the light of the Periodic Classification and modern methods of checking or determining atomic weights clearly indicate for beryllium an atomic weight of about 9.1 and a valency of 2. Anode-ray analysis indicates that beryllium is a " simple element " with an atomic weight of 9.0 ± 0.1 (Na = 23).
|Beryllium as well as its neighbors, lithium and boron, is relatively low-abundant in the Earth crust, its concentration is approx. 2x10-4%. In spite of that beryllium is not a trace element. Beryllium is found in a number of minerals such as beryl in pegmatite surface deposits, crystallized in the granite domes. It is known about gigantic beryl crystals 1 meter long and with weight several tons. |
Beryllium is an essential constituent of about 54 minerals, the most important of which is beryl [Be3Al2(SiO3)6]. It forms many colored varieties. Aquamarine and emerald are precious forms of beryl. Emerald is colored green by 2% of chromium. Aquamarine has a delicate blue or turquoise color due to iron (II) impurities. If it contains manganese instead of chromium, beryl becomes pink morganite, and iron (III) ions make the beryl, called heliodor, yellow.
The most important industrial beryllium minerals are also phenakite 2BeO•SiO2, bertrandite (Be4Si2O7(OH)2), and helvite (Mn,Fe,Zn)4[BeSiO4]3S. On average, world's beryllium resources are estimated more than 80 thousand tons (corresponding to the beryllium content) 65% of which are localized in the USA. The main deposits are in Spor Mountain, Utah, which is the main supplier of bertrandite ore in the world, approximately 19 thousand tons in the end of 2000. There is an insignificant amount of beryl in the USA. In other countries the biggest suppliers of beryllium are China, Russia and Kazakhstan.
Beryllium apparently does not play any significant role in living processes. Its content in the average human being organism is approximately 0.036 mg, each intake with the food - around 0.01 mg.