Beryllium or Glucinum

BERYLLIUM or GLUCINUM, a metallic element with relationships to magnesium, zinc and aluminium. (Symbol Be, atomic number 4, atomic weight 9•0 2 ; no isotopes.) Beryllia was first isolated from beryl in 1797 by Vauquelin, whereas Wohler, Bussy and Debray were the first to isolate the element itself in impure powder form by the decomposition of its chloride with sodium and potassium. Later, Lebeau obtained this element by electrolysis of a fused mixture of sodium and beryllium fluorides carried out at a comparatively low temperature (incipient red heat) in nickel crucibles, the product being in the form of tiny leafy or fern-like particles. By this process the yield is low, and subsequent refinements neither increased the yield nor im proved the purity of the fused metal obtained by melting down the fine particles into a compact mass.

Electro-metallurgy.

Although probably the first preparation of metallic beryllium by electrolysis at a temperature high enough to melt the product is that of Liebmann, yet much more recently Stock and Goldschmidt have produced by more effective methods fairly pure fused metal by high-temperature electrolysis. They electrolyse beryllium fluoride dissolved in a fused mixture of sodium and barium fluorides in a graphite pot with an iron rod dipping into the middle of the melt. The electric current is passed between the pot and the iron rod through the melt so that beryl lium is precipitated on the iron, the temperature of the pot being kept sufficiently high to melt the deposit into a compact mass. For pure beryllium a temperature of 1,28o° C. must be reached and, as there is normally at this temperature a rapid loss by evap oration and not a little commotion in the melt, much experience is required for the satisfactory and continuous working of such a method.

At the National Physical Laboratory, Teddington, England, a process similar in principle to that outlined above has been closely studied for a number of years and the inherent defects have been overcome. This research shows that the production of beryllium by the improved method would cost little more than the analogous process in regular use for the manufacture of aluminium, provided pure beryllia could itself be procured as cheaply as alumina. Useful though beryllium metal would be, it is unfortunate that no very considerable deposit of beryllium minerals has ever been located. The largest deposits as yet known are of beryl containing no more than 4 or 5% of the metal. Absence of demand and difficulty of identification have been re sponsible for a serious lack of information concerning the occur rence of beryllium minerals. This deficiency should be less felt in the future now that knowledge of the properties both of the element itself and of its various alloys and minerals is increas ing.

Properties and Uses.

The application of beryllium as an industrial metal is still in its infancy. The metal is unique in be ing lighter than aluminium and practically as light as magnesium (sp. gr. 1.84), and having a much higher melting point (1,28o° C.), higher corrosion resistance, and greater hardness than either of these elements.

Beryllium is of a dark steel-grey colour; it takes a high polish which, however, appears to have no exceptional reflectivity for white light. Its hardness is evidently dependent to an unusual extent upon its purity, and as prepared at the National Physical Laboratory (99.9% purity), it is as hard as 0•20 carbon-steel, probably owing this hardness and also its brittleness to some specific impurity. Like aluminium, the metal combines vigorously with many other elements but becomes inert to corrosive and other influences through the formation of a fine protective film of oxide of a very tenacious and inactive nature. Beryllium may be sublimed or distilled rapidly at a temperature not far removed from its melting point.

Alloys with copper, silver, iron, aluminium, etc., have been investigated with interesting results, although much work re mains to be done before commercial demands will arise for any of these materials. Its lightness, high melting point, hardness, and heat conductivity point to possible application in the construc tion of pistons in motor-car and aeroplane engines where cost is a minor consideration. The ductile metal, or a beryllium-rich alloy with some other metal or metals, might supplant aluminium for many purposes where lightness, strength, and corrosion resistance are essential as in all aero-construction. Alloys with iron are being investigated and an untarnishable silver-beryllium alloy has been recorded.

Chemistry of Beryllium.

The Copaux method of extracting beryllium salts from beryl and other silicates is worthy of note in that these refractory minerals are thereby treated cheaply, with remarkable ease, and with a high yield. The method consists in heating at 85o° C. a mixture of finely crushed beryl or other mineral and crude sodium silicofluoride (which is a cheap by product of artificial phosphate manufacture from fluorapatites). Hot water washings dissolve beryllium salts from the mass, leaving in the residue both alumina and silica.

The unique behaviour of beryllium salts in dissolving large quantities of beryllium hydroxide has been put to good account in a novel method for the purification of beryllium solutions and separation of compounds. So remarkable is this property that there are but few salts of beryllium which can be crystallized out of solution, as are the salts of other elements. The usual product of attempted crystallization is a gummy mass of highly "basic" and very variable composition. This peculiarity of beryl lium salts has undoubtedly hindered the progress of beryllium chemistry.

Inorganic Compounds of

Beryllium. Beryllium oxide (beryllia) . The compound of beryllium and oxygen is usually ob tained as a very refractory white powder which can be volatilized in vacuo at a high temperature. A small percentage is contained in the mixture of oxides used in incandescent gas mantles. At the National Physical Laboratory it has been found possible to use beryllia in the form of crucibles for melting and subliming pure beryllium metal without contamination. These crucibles are made by compressing a mixture of beryllia and gum in moulds of the desired shape. After removal from the mould and drying, they are fired in a ceramic kiln to 1,5oo° C.

Beryllium chloride is formed by passing dry hydrogen chloride over the heated metal. It is prepared by the action of the phos phorus chlorides, sulphur chloride, or preferably carbon tetra chloride on beryllia at 700-800° C. (C. Matignon and M. Piettre). It is a white, crystalline, hygroscopic solid melting at about 400° C., and is very soluble in water with formation of hydro chloric acid.

Beryllium iodide, prepared by the action of iodine on the metal in a vacuum at about 300° C., is a colourless crystalline solid which volatilizes below its melting point (5 r o° C.) . It is soluble in water with formation of hydriodic acid. By introducing the vapour of the iodide into an evacuated vessel in which is sus pended a thin tungsten wire electrically heated to about 700° C., dissociation takes place into iodine and beryllium, the metal being deposited on the tungsten in a very pure form. The diameter of the wire can be increased by deposition from o• 1 mm. to 4 or 5mm.

Beryllium fluoride remains as a glassy transparent mass on heating the double fluoride of beryllium and ammonium, and is extremely hygroscopic. The beryllium halides cannot be crys tallized from aqueous solutions.

Beryllium sulphate is prepared by the action of sulphuric acid on beryllia. The excess of acid is removed by evaporation, the residue being dissolved in water and poured into alcohol, where upon the sulphate slowly separates. To ensure freedom from acid, two or more crystallizations from alcohol are necessary, the salt being finally crystallized fron water. It consists of colourless crystals containing water of crystallization. Its aqueous solution dissolves large quantities of beryllia when treated with the hydrox ide or basic carbonate.

Organic Compounds of Beryllium. Basic

beryllium ace tate produced by dissolving beryllium hydrox ide or basic carbonate in acetic acid, is insoluble as such in water but soluble in such organic solvents as glacial acetic acid, chloro form, ether and alcohol. From these solutions the compound separates in well-defined crystals belonging to the cubic system. These crystals have a definite melting point and can be distilled unchanged under normal or reduced pressure. When subjected to X-ray examination, the component parts of the basic acetate mole cule are found to be arranged as follows. The lone oxygen atom is placed centrally, the four beryllium atoms occupy the four vertices of a regular tetrahedron, and the six acetate groups span symmetrically the six sides of this regular solid. Homologues have also been prepared and examined (Morgan and Astbury, 1926), namely the propionate, n- and iso-butyrates, and pivalate (trimethylacetate). These derivatives are also readily soluble in organic media.

Beryllium acetylacetone, an other co-ordination compound, is also insoluble in water but sol uble in organic solvents; it melts and distils without decomposi tion. In this substance beryllium is in fourfold association with two ring-forming radicals (chelate groups).

Beryllium benzoylpyruvate, a similar co-ordination compound, has been shown by Mills and Gotts (1926) to exist in two op tically active forms, thus estab lishing the fact that these arrangements of four associating units round beryllium are not uniplanar but tetrahedral. (See STEREO CHEMISTRY.) In the foregoing co-ordination compounds, beryllium is not com bined directly with carbon but only indirectly through oxygen. True organo-metallic derivatives have, however, been obtained in which the metal is attached directly to one or two organic radicals. Earlier workers (Cahours, 186o, and Lavroff, 1884) have indicated the probable existence of such beryllium compounds, and Gilman and Schulze (1927), by using anhydrous beryllium chloride with the appropriate Grignard reagent (q.v.), have definitely identified beryllium dimethyl as a snow-white solid subliming at 200°, and beryllium diethyl as a colourless liquid m.p. 12 °, b.p. both being spontaneously inflammable in air. These observers also obtained beryllium di-n-butyl and the corresponding diphenyl together with compounds of the type R.Be.X, where R is an alkyl or aryl group and X is bromine or iodine. (See ORGANO-METALLIC COMPOUNDS.) See "Beryllium," Trans. Faraday Soc., xxii. (1926) ; C. L. Parsons, The Chemistry and Literature of Beryllium (1909).

(H. A. S. ; A. C. V.)