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Production of metallic beryllium Morel, Roy Waldo Frederick 1941

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•h. PRODUCTION OF METALLIC BERYIilTM by Roy Waldo Frederick Morel A Thesis submitted f o r the Degree of MASTER OF APPLIED SCIENCE m CHEMICAL M G H T E E R U G The University of B r i t i s h Columbia A p r i l , 1941. A Sable of Contents Page Preface »««««•»«••»»»•••••••••••«••»••••••••••••••••• 1 Part I* A study of "beryllium Occurrence of beryllium ............................. 3 Properties of beryllium 4 A. Chemical . . . . ( . . . . . . . . . . • . . . . . • . . . . . . . . . • . . . 4 S. Physical .•....*•...•..»•...•.........• ••••. 4 Alloys .. 8 Production • « .. 11 A. Reduction by metals 11 B. Reduction by high temperature e l e c t r o l y s i s .. 11 C. Reduction by low temperature e l e c t r o l y s i s ... 13 Part I I . Experimental electrothermal reduction Bs. uh. • »*•«•»»*•««••«*«••*•*»*••«•••••«••••«•«••»«•.«»• X4; CIMAC i"b 2. © •««*««*•«««•*•«««••• X5 3H1©ct}3?o&©s •*** ••»•••••••••••»•••••*•••••••••••*••••• 15 Design of cathode ................................... 17 Furnace design i . . . . . . . . . . . £0 A. Furnace 20 B. A i r and gas supply ...........*.........«... 21 C. Furnao e t r i a l .«.««.«««•«•«•«...«.«««««....... 23 Graphite treatment ....•••..••....»• 24 Part I I I . E l e c t r o l y s i s i n organic solvents Conductivity measurements 26 A. C i r c u i t 27 B. Test of bridge ............................. 28 C. Determination of c e l l constant Beryllium-basic acetate ..•*...•.. A. Preparation of the s a l t 29 31 B. Solution q u a l i t i e s Beryllium benzene sulphonate Bibliography 3 4 * • • * « • « , * « « e • 551 32 •33 1 Preface The main endeavour of this work was to f i n d a suitable, easier method of producing metallic "beryllium. To date there are numerous patented methods i n Great B r i t a i n , the United States and Germany, a l l of which produce either beryllium or i t s a lloys by high temperature e l e c t r o l y s i s but not without considerable d i f f i c u l t y . Ho method has been found for a successful cold temperature e l e c t r o l y t i c extraction of the metal* •1 C. L. Parsons has emphasized what he called "the vagaries of beryllium", meaning, "those p e c u l i a r i t i e s of the element which stand out prominently as characteristic of 2 i t s e l f " . The l i t e r a t u r e of beryllium i s greatly overburdened with compounds, t o t a l l y f i c t i t i o u s , which have "been obtained from analyses of s o l i d phases, mixed crystals, and gummy indef i n i t e precipitates of varying degrees of b a s i c i t y . It i s , therefore, not surprising that the i s o l a t i o n of beryllium has been somewhat hindered. On the subject of beryllium the results of the German workers were greatly respected. However, the American l o u i s L. S t o t t 1 3 , W. L. F i n k 1 4 , etc. whose a r t i c l e s , f o r the most part, appear i n the "Transactions of the American Institute of Mining and Metallurgical Engineers," have given us the only published data since 1929. With this i n mind, I have taken the l i b e r t y of choosing what I considered most probable data. This thesis, although primarily concerned with e l e c t r o l y t i c beryllium, embodies considerable references to the l i t e r a t u r e of beryllium, merely to aid future work and possible duplication. 5 Part I , A;Study of Beryllium Occurrence of "beryllium Table I l i s t s the various quantitative, occurrences of "beryllium "but i t should "be "borne i n mind that of these minerals only beryl has been successfully worked. This was due to the sodium s i l i c o - f l u o r i d e process f o r attacking beryl, brought out by Copaux. It i s quite probable that there are other minerals, higher i n b e r y l l i a content and easier to manipulate, since many rock analyses have taken beryllium for aluminum which, chemically, i s quite similar. Table I. Mineral Formula ^ B e r y l l i a Beryl 3Be0.Al 20g.6Si0 2 4.65 Suclase 2Be0.Al 20 3*2Si0g,H 20 16.97-21.78 Phenacite B e 2 S i 0 4 44.46 Bertrandite Beg(BeOh) 2Si 20 7 40-43 Chrysoberyl Be(A10 2) 2 19-20 Beryllonite lfaBeP0 4 19-20 Herderite BeCaFP0 4 15-16 Hambergite BeOH.BeBOg 53 Meliphane F a C a 2 B e 2 F S i 3 0 1 0 10-14 Epididymite ' HNaBeSi s0 8 10-13 Gadolinite F e B e 2 Y 2 S i 2 0 1 0 5-11 Helvite (Be,Fe,Mh) 7 S i s 0 1 2 S 13-14 From th i s "brief table, by no means complete, i t becomes apparent that of a l l minerals to choose, irrespective of ease of extraction, beryl has the lowest b e r y l l i a content, requiring considerable treatment of valueless gangue material. • Properties of beryllium A-. Chemical The chemistry of beryllium i s well summed up by C.L. 1 .. • P Parsons and by J". W. Mellor . Perhaps the most s t r i k i n g 4 5 feature i s the very low atomic weight of 9.018. ' From the standpoint of materials of construction the most stressed chemical feature i s corrosion resistance. Beryllium i s less basic than magnesium and i s only very slowly attacked by hot water to a limited extent. Its oxidation i n a i r i s a slow process. Dilute hydrochloric, sulphuric or n i t r i c acid attack beryllium with the evolution of hydrogen. However, i n i t s metallic state beryllium, l i k e aluminum, i s coated with a protective oxide coating which renders the metal passive to e l e c t r o l y t i c corrosion. On th i s account beryllium has the same valve or r e c t i f y i n g action on alternating current that aluminum possesses. B. Physical Beryllium i s a l i g h t , s t e e l grey colored metal with a bright luster quite similar to a good s t e e l . The s p e c i f i c gravity i s 1.85. There i s no record of an actual determinati of Young's modulus of e l a s t i c i t y but, by Fessenden's law, i t has been estimated to be 30,000 Kg. per sq.. mm., or about 30 percent higher than s t e e l . The available physical constants are given i n Table I I . Table I I . Atomic Number 4 Valence 2 Atomic weight 9.018 Melting Point Specific gravity 1285°C 1.85 lin e a r c o e f f i c i e n t of expansion 20( - 100° 12.3 10" 6 - 200° 13.3 i o - 6 - 300° 14.0 10~ 6 - 400° 14.8 10° 6 - 500° 15.5 1G~6 - 600° 16.1 10~ 6 - 700° 16.8 i o " 6 Heat conductivity E l a s t i c Modulus Heat of Fusion Crystal type Hardness K = 0.3847 0.000751t - 0.000000468t2 - 0.0000Q027t3 30,000 Kg. per sq.. mm. 345.5 c a l . per gram hexagonal close pacx 120-30 B r i n e l l 7 (99.8 - 99. I l l B r i n e l l 8 (99.95$) 60-65 B r i n e l l 9 (99.99$) 6 o Vapor pressure ,001 mm. Hg at 1400 0 5 mm. Hg at 1530°C 760 mm* Hg at 3040°C E l e c t r i c a l conductivity 5.41 10 4 mhos, at 20°C It w i l l be noted that the hardness varies with purity very r a d i c a l l y . This, as i n zirconium, thorium, and titanium, i i s the result of a beryllium--beryllium oxide eutectic occurring | i n the grain boundaries of the crystals, as f i r s t suggested by I :. •' „ 10 I A. E. van ArJcel. This eutectic i s responsible as well f o r j the brittleness of c h i l l cast specimens of 99.8 to 99.9$ Jl beryllium. According to J* A. Sloman s u f f i c i e n t l y pure | beryllium has a certain amount of d u c t i l i t y but his observations if were carried out on minute p a r t i c l e s and have not been dupli-ft • il cated. Pure d i s t i l l e d beryllium may be hot-rolled very poorly j down to sheets .02 i n . thick. When hot i t can be bent somewhat 1 but at ordinary temperatures the elongation i s very low. Since pure beryllium i s so extremely b r i t t l e and generally not workable, i t finds no use as a structural material. The applications of the metal have been limited to the e l e c t r i c a l f i e l d . The metal has a transparency to X-rays 11 | nearly 20 times that of aluminum and i s hence used for i windows i n X-ray tubes. The very low tendency of the metal to 12 sputter i n cathode-ray tubes i s valued with the recent commercial exploitation of these tubes. In connection with e l e c t r o l y t i c work the electrode potential of beryllium i s desired. From the decomposition potential of molten BeClg the potential at 25°C i s -.804 v o l t s . By d i r e c t experiraental u S i n g a * „ y l l i m a^algan, 1 7, Prytz found the potential of -1*96 volts assuming- a bivalent 18 ion formation. W. M. Latimer calculated the potential as -1.67 volts with an accuracy of 1$ from the entropies of the ions i n a hydrous solution and the heat of solution of 19 beryllium i n acid. The most recent value, that of Getman obtained experimentally from a c e l l involving a beryllium electrode i n contact with a beryllium perchlorate solution, gives -I*13 v o l t s . In view of the f a c t that Getman's figure i s the l a t e s t i t s h a l l be assumed that his i s correct. This places beryllium below calcium, magnesium or aluminum i n the electromotive.series. There i s considerable doubt as to whether beryllium forms a monovalent or divalent ion. 20 According to the work of J. M. Schmidt on the conductivity of BeClg i n organic solvents, i t appears that, depending on the solvent, one valence form occurs for concentrations up to one mole, per l i t r e , whereupon a t r a n s i t i o n takes place and the other valence form exists. This was suggested q u a l i t a t i v e l y by Getman i n his a r t i c l e . According to Bodforss 2 3 also, the electrochemical behaviour of beryllium i s anomalous. As the electrolyte becomes more d i l u t e the potential of the metal becomes increasingly positive or more noble, contrary to the normal behaviour of metals. The halogen ions tend to render the potential strongly positive, a characteristic of third group metals. Bodforss suggests the two valenced ion of beryllium to account for t h i s . 8 Alloys ; Perhaps the best known of a l l alloys of beryllium are those of copper, aluminum, s i l i c o n , iron, n i c k e l , and 15 various ternary copper-base a l l o y s . Some of these y i e l d very high t e n s i l e strengths and, what i s more important i n machine design, the r a t i o of y i e l d point to ultimate strength i s abnormally high without impairing the r e s i l i e n c e or elongation. Table I I I Physical Properties of Sand-east Alloy of 0.4$ Be, 2.6$ Co, balance Cu, af t e r Heat-treatment. Ultimate tensile strength, l b . per sq.» i n . 95,000 E l a s t i c Limit, l b . per sq.« i&« 85,000 Elongation, $ i n 2 i n . 7 Hardness, Rockwell B, 100-Kg. load 97 E l e c t r i c a l conductivity, $ of. Cu* 45-50 This a l l o y does not give the t e n s i l e properties or hardness of binary copper a l l o y s but o f f e r s a good combination of heat resistance, toughness:, conductivity and hardness* Table IV Sand-cast 2.75$ Be-Cu after heat-treatment. Ultimate t e n s i l e strength, l b * per sq.. i n . 1509000 Ultimate compressive strength, l b . per sq.. i n . 190,000 E l a s t i c l i m i t , l b . per sq.. i n * 135,000 Elongation, $ i n 2 i n . 1 Hardness, Rockwell C 40-42 The casting q u a l i t i e s and the good flowing cha r a c t e r i s t i c s of t h i s a l l o y make i t suitable for cast molds i n the p l a s t i c industry where ornamentation i s at a premium i n molding. Table T Mckel-base Alloys A* Be-Ei : 1.7-1.9$ Be B. Be-Fi-Cr-Fe : 60$ III, 15$ Or, 7$ Mo type, 0.6 to 1$ Be. (Be contracid) A. Heat-treated B. Heat-treated from hard r o l l e d from hard r o l l e d Y i e l d Point, l b . per 'sq.. i n . £13,000 213,000 Ultimate Strength, lb. per sq.. i n . 260,000 263,000 Elongation, $ i n 100mm. 8.3 6.0 B r i n e l l Hardness 460 430 These alloys show the effects of heat treatment quite well. When quenched soft the B r i n e l l hardness value approxi-mates 175 with a y i e l d point of 55,000 per sq> i n . and an ultimate strength of 120.000 per sq.. i n * These nickel-base alloys combine outstanding toughness with high t e n s i l e strength, even surpassing properties of good a l l o y steels. The contracid beryllium a l l o y possesses s t a b i l i t y of hardness even a f t e r prolonged heating at the precipitation-hardening temperature. It i s corrosion resistant and non-magnetic. It has thus been adopted for main springs i n watches i n place of watch-spring s t e e l . Beryllium-copper alloys of 2.25$ beryllium make excellent spring metal. The springs can be formed i n li g h t temper and then hardened by simple low-temperature heat-treatments to y i e l d more stable spring-properties than with steel or phosphor-bronze. Alternating stress endurance of st e e l i s about ten m i l l i o n cycles but contact springs of Be-Cu 10 show no fatigue a f t e r several m i l l i o n cycles. Users of this a l l o y report lower creep and e l a s t i c hysteresis than i n any other commercially available a l l o y . H e l i c a l springs of 2.25$ Be-Cu, combining low torsion modulus with high e l a s t i c l i m i t are useful where large deflections are required. Static loads of 100,000 per sq.. i n . can be carried without permanent set, I and up to 40,000 per sq..' i n . where fatigue i s a faotor. As for one of a m u l t i p l i c i t y of uses, take the landing gear of an aeroplane* The suspension spring of the landing gear must be capable of withstanding sudden heavy impacts with no danger of fracture. Be-Cu alloys meet th i s requirement with ease* The wearing resistance of the 2.5$ Be-Cu al l o y i s unusually h i g h — b e t t e r than f i v e times that of bronze against s t e e l . The a l l o y i s excellent for moderate speeds and. low-bearing pressures where lub r i c a t i o n i s poor. It seems to have a film-forming capacity with s e l f - l u b r i c a t i n g q u a l i t i e s . This quality also handles extremely high-bearing pressures at low-bearing speeds* High-bearing speeds with heavy loads cause seizure of the shaft but i f an analogy i s taken from lubrication design, J( - 476 x 10-i0.(pr).(-o.) + *002 r c o e f f i c i e n t of bearing f r i c t i o n . Z ; o i l v i s c o s i t y . H" - revolutions of shaft. p s bearing pressure. d s shaft diameter, c s clearance. - bearing modulus* P 11 i t "becomes evident that the heat generated i n a "bearing i s inversely proportional to the diametral clearance at constant "bearing modulus. More work i n this f i e l d w i l l show i f this alloy; requires different clearances than are standard with phosphor-bronze, etc. bearings. In this way seizure may possibly be overcome. Production A. Reduction by metals The production of beryllium by chemical reduction i s p r a c t i c a l l y of h i s t o r i c a l interest alone. The one exception E l suggested i s a method patented by H. S. Cooper. Magnesium chips are added to a KCl-laCl bath containing 25$ BeClg at a temperature of 6'5Q°C. The melt i s cooled and water leached giving a 75$ y i e l d . The low-working temperature as well as the low percentage of beryllium are valuable i n reducing v o l a t i l i z a t i o n losses. / With this last method i s the rather unsatisfactory 2 method of H. Goldschmidt f o r reducing the oxide with aluminum. Both reduction methods show no commercial application, but some importance must be attached to them. As the reduction of beryllium was poor, i t may be inferred that beryllium i s just below aluminum i n the electromotive series. B* Reduction by high temperature e l e c t r o l y s i s The number of methods of producing beryllium at high temperatures from various s a l t s , mainly oxyfluorides i s astounding. The B r i t i s h Chemical Abstracts since 1930 w i l l v e r i f y the number of patents of such processes f o r Great 12 B r i t a i n alone* Yet every method has some drawback such that today the market price of beryllium i s quoted at #15.00 per pound. Contributing'to the expense of the metal are the low equivalent weight of the metal, processes with current e f f i c i e n c i e s never exceeding 50 percent, high raw material cost, and high operating temperatures r e s u l t i n g i n extreme v o l a t i l i -zation losses. With consideration to fluoride processes, the main requirements may be stated b r i e f l y as follows: a. Bath temperature and composition. The metal should be deposited on some suitable cathode at or above i t s melting point, that i s above 1285°C. In contrast to the eleotrodeposition of aluminum, i t has been stated that the reduced metal cannot be tapped o f f as a layer by v i r t u e of a difference i n specific; gravity between the bath and the metal. This, I believe, i s not correct. The higher the bath temperature, the more compact deposit i s formed, but more e b u l l i t i o n of the melt occurs with consequent vaporization losses. This i s not as serious as i t might seem since inert s a l t s of high melting point, such as Balg i n the case of f l u o r i d e processes, can be introduced to reduce the e b u l l i t i o n . There i s an optimum addition quantity, as might be expected, 24 determined by the experimental current yields of beryllium, b. Source of heat The bath temperature required c a l l s f o r an e f f i c i e n t heating system. As 1350°C i s required i n the melt the furnace i n t e r i o r should be at least at 150Q°C. Gas or e l e c t r i c heating 13 i s suggested. An anode or cathode arc method of heat source i s permissable on a laboratory scale but not i n d u s t r i a l l y , c. Power The direct current for e l e c t r o l y s i s should be available at a-voltage as high as 80 v o l t s . Although the normal voltage required i s from 8 to 10 v o l t s , the f l u o r i n e gas mantle formed at the anode gives a high anode resistance whereupon a high voltage is.required to pierce the mantle* Extreme instrument flu c t u a t i o n must be expected, i f this i s the case, and, what i s more, the e l e c t r o l y s i s w i l l not be very orderly. 0. Reduction by low temperature e l e c t r o l y s i s Owing to the hydrolyzing properties of beryllium sa l t s , aqueous solutions are not very promising. The beryllium ion, though very small, yields an abnormally low ion mobility due to very strong hydration. This d e f i n i t e l y outrules the use of aqueous solution since only the hydroxide forms on deposition of the metal. Only non-aqueous solutions may be used and the number of beryllium compounds soluble i n organic solvents i s limited. Furthermore, the small d i e l e c t r i c constants of organic solvents are usually too low to produce the ionization required f o r e l e c t r o l y s i s . Even so, i t was decided to try some of these s a l t s — t h e basic acetate and the benzene sulphonate. According to Dr. Hellmut Fischer the acetate and i t s homologues are non-ionized i n such solutions. To v e r i f y this statement i t was decided to repeat this work. 14 Part I I . Experimental electrothermal reduction The experimental production of beryllium w i l l be 25 oarried out according to the method of A. G. Vivian. The start i n g material obtained was BeCOgi 4Hg0 made by Eimer a.nd Amend. As a test of purity a spectrum analysis was run on the material (See Plate). The main impurity was sodium but, since sodium shows up so well spectrographically, the estimated amounts of sodium would be small. Faint traces of lead, magnesium and praseodymium were found and surprisingly enough, no aluminum, the one element most expected. Bath" A mixed flu o r i d e bath i s employed f o r the e l e c t r o l y s i s . A double f l u o r i d e , BeFg.HaF, i s made by mixing i n a graphite pot equivalent quantities of BeC0g.4HgO and anhydrous KagGOg with an excess of 48$ hydrofluoric acid. After complete s t i r r i n g the product i s dried, then placed i n a graphite crucible i n a gas-fired furnace to fuse at 650°C. The fused product i s poured into a preheated graphite ladle where i t i s skimmed before pouring onto a hot pouring plate. In this procedure the double fl u o r i d e i s cast into small sticks "the suitable for feeding^electrolytic bath. To lower the e b u l l i t i o n of the bath a 10-15$ barium f l u o r i d e addition i s made. zz££ z>g ssasr y y • 15 Crucible The crucible f o r the el e c t r o l y s i s i s a graphite pot-treated on i t s exterior with a thin layer of refractory Thermolith applied with a brush. This layer saves the pot from burning and actual corrosion from wear by hot-moving furnace gases, and i s not too thicJc to materially interrupt the heating of the melt. On the upper rim of the crucible i s a close-f i t t i n g , water-cooled l i d equipped with two suspensions for graphite anodes shaped to allow feeding of the bath material* The crucible, water-cooled l i d and anodes are a l l e l e c t r i c a l l y connected to form the anode system. Eleo'trodes Gasification of graphite electrodes occurs at an arc temperature of about 5525°C. At the arc, carbon vapor conveys the current to the melt. Quite naturally the resistance of the carbon vapor gap i s considerable i n comparison with the c i r c u i t involving only carbon-melt contact. A high voltage drop may be expected due to the arc. Further, fluorine i s liberated at the anode giving a combined carbon v a p o r — f l u o r i n e gas arc f i l m . Since a cold melt w i l l c h i l l the arc and interrupt the g a s i f i -cation of the carbon at the electrode surface, i t i s to be expected that the heating effect of the arc w i l l increase with the heating of the melt i t s e l f . This means that higher operating conditions serve to maintain a continuous arc. 2ft Borchers gives values of current density required to maintain steady arcing i n terms of electrode cross section. With 2 5 electrodes, l£"X i&n or .94 sq. i n . a current density of 70 amps. 16 per sq. i n * or a current of 66 amps, i s required. Assuming that as much as two-thirds of the: current i s carried by the electrodes and one-third by the crucible, then 1GG amps, w i l l be s u f f i c i e n t for steady electrolyzing conditions. Other workers seemed to have d i f f i c u l t y at t h i s point and i t seems that t h e i r current densities were not s u f f i c i e n t l y great enough f o r steady arcing. Considerable carbon finds i t s way into the melt through the direct-arc type of heating where the carbon i s subdivided i n the,vapor state. Since carbon i s a decided impurity i n obtaining pure beryllium, i t would seem wise to eliminate this type of heating from the e l e c t r o l y t i c c e l l . This could be greatly reduced i f the crucible were to serve as the only anode, the two aux i l i a r y anodes being eliminated. The weight of the melt w i l l seriously hamper the arc formation at the bath-crucible contact. The ef f i c i e n c y of the anodes i s dependent on their length and on increasing current densities. There i s a l i m i t to the l a t t e r because of overheating which may be s u f f i c i e n t to destroy surrounding material, be i t iron, refractory, etc* The length i s determined by three factors: a. Breaking of electrodes: Breaking, i n general, w i l l not occur i f cross sections and current densities are low. Since the electrodes are made of graphite, with a s p e c i f i c conductivity ten times that carbon, high current densities are permissable. Electrodes should not be placed cold into the melt since chipping w i l l invariably occur. 17 b. Arc formation which gasifies the graphite: Nothing can be done about t h i s , since i t i s an inherent characteristic of the arc. c. Oxidation: According to Moissan s o l i d graphite oxidizes at 640°C. The only preventative i s an inert atmosphere or r e l a t i v e l y cool exposed portions of the electrode. A reducing atmosphere w i l l aid reducing anode loss, but then there w i l l be .insufficient oxygen to burn out carbon at the surface of the melt and the cathode picks carbon up, co-depositing i t with tbs. beryllium. This condition of oxidation then i s also a necessary e v i l . As a result the electrodes used must be renewed at intervals of roughly 7 hours. Design of cathode A sketch of the cathode shows the various integral parts* It rotates and at the same time slowly l i f t s i t s e l f out of the bath. The steel rotating cathode sleeve i s f i t t e d at i t s lower extremity with a grub screw into which f i t s a beryllium starting t i p . So that the t i p w i l l not a l l o y with the steel sleeve, the cathode i s water-cooled. The piping for cooling serves as the shaft for the sleeve. Two bearings sweated onto the shaft centre the r o t a t i o n of the sleeve. For a good e l e c t r i c a l and heat contact from piping to sleeve mercury i s introduced between the two. It now becomes necessary to get an idea of what heat must be supplied to maintain the bath at" i t s correct temperature. [5 Rotating Ca thode Sec-flon on $ $ / / . *• < 1 I5'C. I At, 4 ^ A ^ j A £ -<*3 £?4 & 7 A ^ A ^ > 18 One of the main items i s the water-cooled cathode. Using the configurations of the accompanying sketch of the cathode I obtained the following figures: Wall thicknesses: L 2 - L 4 = L Q = (_|) (_|) « .0052 f t . For six inches of cathode: 9. 1 A7 - H " A 5 = ( g g j j l * .075 sq.. f t . 12 A 4 = (|§)— * .090 sq.. f t , A l = A2-..Ai5 * ( i f ^ i 2 • ' • 1 0 6 S(*» f t * Film c o e f f i c i e n t s : h-^  - hg - hg - 150, which i s a high value, hence amply adequate. h7 - 2200, taken f o r 360 l b . of water per hour per .131 f t . periphery. Heat conductivities: kg s 21 • B.t*iu/hr*/sq> ft./°F. k 4 = 4.8 ke s 26 Now i f the to t a l resistance to heat flow i s given by Rj, then RQ} s % + Rg + Rg R 4 + R 5 + R^ + R 7. Let us assume for simplicity that six inches of the cathode are t o t a l l y immersed i n a molten bath at 1300°C, and the cold water i s at 20°C. Bath f i l m RT R — L _ - .0628 1 *1 A1 19 Steel Hg film. Hg Hg f i l m Steel Water f i l m R2 = _ 2 s ,00234 R>* — R4 = fc2A2 1 h 3 A g £4 h 5 A 5 '6 R7 — k 6A 6 1 - .0628 • .01205 s .0887 : s .00302 s .00607 • 238 Heat required - q - *l-*2 - 2372-64 "* ' R T " .238 = 9700, B.t.u./hr. = 162 B.t.u./min. Now i n the "vaporous space above the melt the average temperature i s perhaps 800°C. In this case we have, for six inches, Ri -, 1 ~ ( h G + h r)A % = R l * % + R 7 = R l .17498 - .804 For f i v e inches of exposed cathode Rrj, - (.804)(|) s .965 q - 3-440-70 = 1 4 2 0 B.t.u./hr. .965 -• 23.7 B.t.u./min. £0 Allowing an effective i i n . of cathode i n the melt 1 = (j) (§) (162) - 6.8 B.t.u./min. Total heat required for cooling water i n the cathode s 23.7 + 6.8 = 30.5 B.t.u./min. I f now the l i d also i s assumed to require this amount of heat, i t becomes evident that the piping i s s u f f i c i e n t l y large to give adequate cooling to preserve metallic parts* An e l e c t r i c furnace was designed to handle this situation but at present a gas-fired furnace i s proving satisfactory. In fa c t , the heat required for cooling may be found d i r e c t l y at the operating conditions, outruling any guesswork required for design of the e l e c t r i c furnace should i t be found necessary. Furnace design A, Furnace A gas-furnace operating as a t o t a l muffle furnace with B. C. E l e c t r i c coke-oven gas was f i r s t designed as shown i n the sketch. This consisted of two iron shells separated with diatomite to lower heat conduction through the furnace walls. The interior"furnace walls were lined with alumina bricks faced with Thermolith. The gas-air mixture i s introduced through a burner near the furnace bottom s t r i k i n g the wall tangentially. Both high and low pressure compressed a i r are used, the former to aid i n supplying s u f f i c i e n t gas, the l a t t e r to complete combustion. To give some degree of mixing and to remove the random eddying, long small-diameter pipes are welded into the burner mouth. 21 B. A i r and gas supply-Exhaust fumes are removed at the top of the furnace at a tangent, the exhaust "being l e d through a heat inter-changer to heat the high compressed a i r . This prevents the undesirable cooling effect of expanding a i r i n the furnace. However, fortune had i t that only a i r at 12 lb. per sq.. i n . was available, this suited for low pressure a i r . For a pressure of 70 l b . per sq.. i n . a compressor was required to supply a 1 — i n . o r i f i c e i n the high pressure j e t . The c r i t i c a l pressure 8 fo r this P„ = .53P, e l = (.53)(70 + 15) - 45.1 l b . per sq.. i n . abs. = 30.1 l b . per sq.. i n . o r i f i c e , which incidentally i s of a nozzle construction, i s 30.1 l b . per sq.. i n . Maximum flow corresponding to the acoustic v e l o c i t y of the a i r occurs through the nozzle. Thermodynamic w 0.532 Apv • w a i r = , x l b . per sec. ( T ^ e where, A - area of nozzle. P i = pressure of compressed a i r . T^ - temperature of compressed a i r relations can be applied to develop the c r i t i c a l flow but only a rough idea can be foretold of the temperature of the compressed a i r , this varying u n t i l the furnace has reached operating conditions. This i s not the grave situation that might be inferred, so that 800° has been assumed for T^. 22 Correspondingly, then the weight of a i r follows: „. 0Y532 .1 ? • TiooT* < 8 5H60) l b . per rain. = 1.18 lb. per min. (14.6 ou. f t . free air) This means that a compressor i s required to deliver 14.6 cu. f t . free a i r per minute at 70 lb. per sq. i n . The available a i r and gas must be taken into account. Gas enters the building i n 6 i n . mains and i s distributed i n smaller 4 i n . pipes. Each room i s fed with 1 i n . pipes. Compressed a i r i s generated with a 40 hp. Hytor compressor, giving a i r at 50 l b . per sq. i n . , this being throttled to 15 l b . per sq. i n . for use i n the building. The higher pressure a i r i s used to operate steam valves so that this source could not be tapped f o r use i n the furnace. The low compressed a i r i s sublet i n 2 i n . pipe, then i n 1 i n . pipe. Unfortunately the plans of the piping are not available so that the resistance to a i r and gas flow are unknown. Assuming that the resistance to flow i s a maximum, that i s , that the pipe diameters are a minimum 1 i n . over a distance of 200 f t . , a l l added resistance must be avoided to supply s u f f i c i e n t a i r and gas for the furnace. The question of valves now enters into the supply of gas. The high resistance of globe or needle valves was against their usage so that gate valves were required. The resistance of the gate valve i s considerable u n t i l the h a l f open position i s reached. This means that poor control of gas mixtures i s given i f much t h r o t t l i n g i s required. Needle valves were t r i e d but s u f f i c i e n t flow could not be maintained. Thus gate valves WBre employed and further burner resistance flow was cut by 23 using a large burner. C. Furnace t r i a l The furnace was tested without the high compressed a i r to get some idea of alterations required. The furnace reached 1450°C i n about two hours, but not with^ad equate A reasons f o r the delay: a. The burning chamber was extremely large to burn the si m i l a r l y large gas supply of some 400 cu. f t . per hour. Poor mixing occurred as a result of th i s , and heat developed i n the regions nearest and i n the exhaust l i n e b. The c i r c u l a r t o r r e n t i a l flame path_in the furnace eddies quickly from the. furnace, since natural flow allowed the hot gases to ris;e and exit. It i s , therefore, advisable to enter the gases at the top of the furnace and draw off the exhaust from the bottom to delay the exit of the gases. c* The surface l i n i n g of the furnace withstood the temperature exceedingly well but cracked and f e l l from the backing i t was protecting. This allowed heavy heat losses to the .exterior. As only 1000°F i s required to fuse diatomite, i t i s l i k e l y that i t may have melted, leaving only an a i r space for insulation, d. Aluminum paint could be used to reduce radiation losses. For the meantime this furnace has been abandoned for a smaller furnace which incorporates the ideas suggested by the f i r s t furnace. However, here only low pressure a i r i s used. 24 The l i n i n g i s IISULBRICK faced with GARBOFRAX. On testing, this furnace i n l-§ hours reached 1490°C with a gas consumption of 240 c.u. f t . per hour. This means ,that the f u e l heat supplied, assuming complete combustion, i s 2 4 0 = 1960 B.t.u. per min. However, the furnace i s always kept :in a reducing condition to preserve as much as possible the carbon pots that are subjected to the flames. Graphite treatment In order to preserve the graphite from excessive oxidation and to prevent i t from introducing impurities to the melt, a l l graphite i s treated after machining to the form required, whether for pots or anodes. It i s f i r s t digested i n fused caustic soda f o r two days. Carbides of aluminum, iron, etc. are attacked y i e l d i n g hydrogen and hydrocarbons which are gradually expelled. A 14-day e l e c t r o l y t i c extraction with continually renewed hydrochloric acid follows u n t i l a l l iron i s removed. The graphite i s water-soaked for several days and allowed to dry. It i s then gradually heated i n sodium chloride, f i r s t of a l l to remove impregnated water. Second, the s a l t i s fused at 90Q°C and the graphite soaked for !-§• hours. Treated pots, after cooling, are given a wash of Thermolith on their exterior to aid wearing qualities i n the furnace. As can be expected, the removal of impurities i s essential, owing to the changeable character of pure beryllium, with small amounts of impurities. The t r i a l s however do not need the rigorous graphite treatment since pure beryllium i s not to be expected at the f i r s t attempt. Thus only the fused 25 s a l t treatment has been carried out on a l l graphite with the exception of one electrolyzing crucible. 26 Part I I I . E l e c t r o l y s i s i n organic solvents As mentioned i n the introductory sections the requirements of beryllium salts i n organic solvents are three-f o l d . F i r s t of a l l water should not be allowed to interfere with the reactions of e l e c t r o l y s i s . If water does form, i t s concentration should be minimized. This i s easily accomplished i f the solvent i s not water soluble, for then water can be drained off, leaving only small amounts of entrained water i n the solvent. Second, the s a l t should be soluble and in connection with beryllium salts this statement should not be under-emphasized. Third, the salt should be Ionized. With low d i e l e c t r i c constants and small electrostatic moments for organic solvents, ionization i s d i f f i c u l t . Before plating of beryllium can occur, ionization must take place. The natural step i s then to test the conductivity of various solutions. Conductivity measurements Conductivities are measured with 1000 cycle a l t e r -nating current i n a standard conductance c e l l , equipped with c i r c u l a r f l a t plate platinum electrodes about 7 cm. apart. To overcome surface effects of polarization and overvoltage, the 2 electrodes are platinized with a Zfo platinum chloride solution. To maintain t h e . c e l l at a constant temperature of 25°0 a 12 gal* water bath was used. . Running water through a copper c o i l immersed i n the bath maintains the temperature very easily at 25°C, using a platinum, resistance thermometer. A. C i r c u i t The conductance, or more correctly the resistance, of the c e l l i s determined with a resistance bridge, using 1000 cycle alternating current i n the bridge and a telephone for detecting the balanoe point of the bridge. To increase the s e n s i t i v i t y of the telephone a type 56 amplifying tube was employed which introduced considerable d i f f i c u l t y due to a hum i n the telephone. Choice of voltage sources and ground wiped out this d i f f i c u l t y . Plate voltage of 90 v o l t s i s supplied by two B batteries. The heater current of 1.5 amp. i s obtained, from 6 v o l t .D. C. lines of battery source. A r e s i s t o r bias of 3200 w. gives the optimum bias of 312 volts with 1 ma. plate current. Coupling this resistor i s a 1 mfd. condenser to minimize the plate c i r c u i t impedance^. A'.1 mfd. blocking condenser i s placed i n the grid c i r c u i t . The grid i s grounded through a .5 meg. r e s i s t o r . The c i r c u i t i s grounded as shown to the water system. External hum was almost obliterated by replacing the usual microphone hummer with a 1000 cycle audio o s c i l l a t o r which gives excellent results i f the internal and external c i r c u i t s ' impedances are balanced. A Le.eds-Horthrup conductance bridge, s e r i a l Ho. 155170, was used to give various resistance r a t i o s . This bridge i s equipped with end c o i l s , for more accurate resistance deter-minations* As a reference resistance non-inductive Leeds-Northrup dial-type resistances (R) are used. The bridge d i a l reads from 0 to 1000 (A). With the end c o i l s not connected 28 the unknown resistance i s given by: X - R £ 1000 - A With the end c o i l s connected the resistance i s : X - R 4 5 0 0 + A 5500 - A When the bridge i s balanced, points (1) and (2) are at the same potential and phase. Hence there should be no current through the grid c i r c u i t , no grid voltage, hence, no signal through the telephone. Off balance, the g r i d receives a signal weak or strong depending on how far off balance the bridge c i r c u i t i s and the telephone receives the amplified audible signal. Obviously then, the balance point i s one of minimum sound* B. Test of bridge Before the set-up could be used i t was.tested against a standard Leeds-Horthrup non-inductive type d i a l r e s i s t o r . Io deviation could be found from the lowest ranges (.1 ohms.) to 10,000 ohms. It i s expected that the solutions to be tested w i l l f a l l within t h i s range, low the conductance c e l l i s tested f o r cleanliness with d i s t i l l e d water. This means that the c i r c u i t should be correct at high resistances. For R a radio r e s i s t o r of 480,350 ohms, was used. This was tested previously on a wheatstone bridge, using a sensitive galvano-meter. As X, a standard leeds/lorthrup resistance i s used. Table VI. R X A X calc. Dev. fa ohms ohms ohms 480,350 100,000 172 99,783 - .217 480,350 110,000 187 110,484 .440 £9 The resistances check as closely as the bridge can be set, so that the radio r e s i s t o r may be used f o r a standard for checking the conductance of water. Various d i s t i l l e d water samples i n the conductance c e l l were tested to ensure that the c e l l was free from impuritie occluded i n the pl a t i n i z e d electrodes. The f i n a l readings for the batch of d i s t i l l e d water were: R 480,350 ohms. A 4£5 thus X - 355,000 ohms. Now the c e l l constant (next stage) i s 1*348 roughly, and thus the s p e c i f i c conductivity of this water was 1 * 3 4 8 , s 3.795 x 10"*6 mhas. 3.55 * 10 5 With this water standard solutions of KC1 are made to determine the c e l l constant. C. Determination of c e l l constant (1) F i r s t standardization with .01 N.KCl. 137275 gm. ZC1 i n 500 c.c. solution* Specific conductance .0014079 mhos* Table V Ll. , st , 1 sample 0nd , £ sample R ohms. A X ohms. Temp. 957.0 500*0 957.000 £5.00°C 950.0 518.0 956.875 960.0 49£.5. 957.1£4 Average X 960.0 49£.0 956.933 Z 956.942 955.0 504*5 956.7£0 957.0 500.0 957.000 The conductance of the solution - — _ _ i . - .00104500 mho. 956.942 Rough c e l l constant * ^0014079 = 1 > S 4 7 2 4 .00104500 Conductance corrected for water = .00104120 mho. The c e l l constant s 1.35219 (2) Check standardization with .02 li.KCl. .7455 gm. EC1 i n 500 c.c. solution Specific conductance = .0027610 mho. st -.nd Table T i l l . end c o i l s i n . R ;ohms. A ohms. Temp. sample 488.8 500 488.800 25°C 490.0 494 488.825 487.0 509 488.756 Average X sample 487.0 509 488.756 s .488.776 488.8 500 488*800 489.5 496 488*717 Conductance of c e l l Rough c e l l constant 488.776 *0027610 - .00204593 ohms. • 1.34949 .00204593 Average rough c e l l constant - 1.348 Conductance corrected for water = .00204213 The c e l l constant a 1.35202 31 Thus for A and B, the c e l l constant r 1.35210 with a mean deviation of 6.7 x lQ"^f0 or beyond the accuracy of weighing. Beryllium basic acetate • . . A. Preparation of the s a l t The basic acetate of beryllium was made from a procedure by 0. L. Parsons 5 modified to suit the occasion. Excess g l a c i a l acetic acid was added to 500 gm. of BeC0g,4Hg0 and mixed. The excess acid was boiled off* The salt i s next redissolved i n g l a c i a l acetic acid and boiled. Certain portions would not dissolve so that the mixture was f i l t e r e d hot. The liquor was discolored so that activated wood charcoal was added and boiled. This was f i l t e r e d , boiled again, and r e f i l t e r e d to remove any traces of charcoal. The excess acid i s now boiled off the liquor, and the liquor set to c h i l l . The basic acetate c r y s t a l l i z e s well and i s easily f i l t e r e d , washed and again r e c r y s t a l l i z e d from cold g l a c i a l acetic acid. It i s then dried at 150°C, ground to a fine powder, and.set to dry again. The product i s kept free from moisture i n a dessicator u n t i l required. The purity of the basic acetate should now be questioned. For a simple test the melting point was determined. This was accomplished by u t i l i z i n g an approved method with a sulphuric acid bath, the acetate being sealed i n thin glass tubing immersed i n the bath. The corrected melting point was 284.3°C which i s just a b i t higher than the recorded value of 283-284°C. This means a high state of purity. 32 As a further test a spectrum analysis of the acetate was taken. This yielded much the same type of spectrum as BeOOg.4HgO with lead, sodium, magnesium, praseodymium and with extremely delicate lines for hafnium, aluminum and s i l i c o n . In a l l , the basic acetate i s pure enough to use for experi-mental work. B. Solution q u a l i t i e s It was decided to make various concentrations of the acetate solutions for conductance work. Solvents were mentioned by C. L.. Parsons and these besides others were t r i e d . Two that were mentioned were not tried-—chloroform, rejected for obvious reasons of price as well as scarcity, and g l a c i a l acetic acid, rejected because of i t s deleterious hygroscopic nature. A l l the others were tested.for ifo solution and i t i s safe to say that only | to i of ifo of the basic acetate dissolved. These solvents include: acetone 3L0 A ethyl acetate 2. amy! acetate 11. .ethyl ether 3. n amyl alcohol 12. gasoline 4. an i l i n e 13. iso propyl alcohol 5. benzene 14. n propyl alcohol 6. iso butyl alcohol 15. pyridine 7. n butyl alcohol 16. toluene 8. carbon disulphide 17. turpentine 9. carbon tetrachloride 18. xylene It i s quite apparent that the German workers i n the f i e l d came to the same "dead-end." 32a. zsszfy/ t"7Z V is s V is I 33 Beryllium benzene sulphonate From the nature of the substance better results are expected from beryllium benzene sulphonate. It has been found necessary to make benzene sulphonic acid f i r s t , then to make the s a l t using either the carbonate or the oxide of beryllium, depending on the s o l u b i l i t i e s of the l a t t e r . The sulphonic acid i s made by slowly adding 625 c.e. of benzene to 800 c.c. of cold fuming sulphuric acid, cooling on every addition of benzene. This mixture i s poured into 3§ l i t r e s of cold water, again cooling during the.process. Any d i phenyl sulphone that forms i s f i l t e r e d o f f . The liquor i s p a r t i a l l y neutralized 5 0 cti OH with 800 .gm. of c r y s t a l l i n e KagCOg. The sodium salt of benzene sulphonic acid i s salted out with 1200 gm. of common s a l t . Warm the mixture to dissolve the precipitated se.lt and f i l t e r hot, with a flu t e d f i l t e r . Cool the liquor with s t i r r i n g to precipitate the s a l t as white c r y s t a l l i n e plates. These are f i l t e r e d with suction and then dried. The product i s weighed and the required amount of 613". sulphuric acid i s added. The benzene sulphonic acid i s f i n a l l y d i s t i l l e d at 137°C with a heated condenser tube to prevent s o l i d i f i c a t i o n of the acid i n the condenser* 34 Bibliography 1. C. L. Parsons "The Chemistry ana Literature of Beryllium", 1909. 2. J. W. Mellor "A Comprehensive Treatise on Inorganic and Theoretical Chemistry", Vol. 4, P. 204. 3. H. Copaux, Compt. rend., 1919, 168, 610. 4. 0. Honigsohmid and L. Birkenbach, "Berichte der deutschen chemischen Gesellschaft", Vol. 55, (1922), P. 4. 5. C. L. Parsons, Jour. Am. Chem. Soe., Vol. 26, 1904, P. 737. 6. B. S. Hopkins and A. -W. Meyer, Trans. Am. Electchem'. Soo., Vol. 45 (1924), P. 480* 7. W. K r o l l : Metal Ind. (July 5 and 12, 1935) 6 and 29. • r 8. W. K o l l : Private communication to Louis L. Stott, of The Beryllium Corporation of Pennsylvania, Reading, Pa. 9. H. A. Sloman: Researches on Beryllium, J n l . Inst. Metals (1932), 49, 365. 10. A. E. van Arkel and J. H. de Boer, Z. anorg. Chem., 148* 4,. 1925. 11. W. Hausser, A. Bardekle and G. Heisen: Fortschritte Gebiete Rontgenstrahlen 35 (1926) 643 K. l l i g . 12. P. D. Kueck and A. Keith Brewer: Cathode Sputtering of Beryllium and Aluminum i n Helium. Review of S c i e n t i f i c Instruments (1932). 13. Louis L. Stott, The Beryllium Corporation of Pennsylvania, Reading, Pa. 14. W. L. Fink, Aluminum Research Laboratories, Hew Kensington, Pa* 15. a Dr. Georg Masing, Dr. Otto Dahl, Dr. Wilhelm K r o l l -Luxembourg: Siemens-Konzern. Louis L. Stott, reference 13* 0 J. Kent Smith, Beryllium Development Corporation, New York, IT. Y., Trans. Aimme, Vol. 99, P. 65. . ^  R. S. Archer and W. L. Fink: Aluminum-beryllium Alloys, Proc. Inst. Met. Div., Aimme (1928), 616. 16. B. Neumann and H. Richter, Z e i t s c h r i f t fur Eleotroehemie, Vol. 31 (1925), P. .296. 17. Fraenkel, Wengel; -and Conn, Z. anorg. allgem. Chem., 171, 82 (1923). 18. W. M. Latimer, Journal of Physiological Chemistry, Vol. 31 (1927)» P. 1267. 19. Frederick H. Getman, Trans. Elect. Soc* Vol. 66, (1934), P. 143. 20. J. M. Schmidt, B u l l , de Soc. Shim. (1928) Vol. 43, P. 49. 21. H. S» Cooper, USP. App. 25-5-35. 22. Prytz, Z. anorg. allgem. Chem., 193, 113 (1930). 23. Bodforss, Z. physik. Chem., 124, 66 (1926). 24. Beryllium: Siemens Konzern as translated by R. Rimbach and A. J. Michel (1932). 25. A. C. Vivian, Beryllium: Trans Faraday S o c , Vol. 22 (1926), P. 211. 26. Wilhelm Borchers: "The E l e c t r i c Furnace" by Rodenhauser, Sehoenawa, Vom Baur. P. 82. 27. Alexander Findlay, P r a c t i c a l Physical Chemistry, P. 156* 


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