The Story of Aluminum Experiment in 1827

Laval University

From the SelectedWorks of Fathi Habashi

2016

The tS ory of Aluminum Fathi Habashi

Available at: https://works.bepress.com/fathi_habashi/189/ Metall-FoMetall-Rubrschungrik

Berlin he repeated successfully Oersted’s The Story of Aluminum experiment in 1827. In 1836 he moved to Göttingen to accept a position at the Uni- versity and in 1845 succeeded in making Habashi, F. (1) aluminum in slightly larger amounts from which he was able to show that aluminum Aluminum was first produced on a commercial scale in France in 1856 by reduction was a light metal. of alumina with sodium. At the same time aluminum bronze was manufactured. Bauxite played an important role in the production of the metal. The French process Aluminum production in France gave way to the electrolytic process invented in 1888. Aluminum became the chief competitor for copper regarding its use in the electrical industry. In the beginning it French chemists were also active in research was more expensive than copper but since the 1960s it became much cheaper. Its to produce aluminum. Henri Sainte-Claire position in the Periodic Table is also discussed. Deville (1818-1881) (Fig. 4) professor of chemistry at the École Normale in Paris produced aluminum in 1854 by electro- aturally-occurring alum used sium and few days later, sodium using this lyzing molten aluminum chloride-sodium by alchemists to enhance the battery. Once these two reactive metals chloride mixture since the mixture has a dyeing of textile was known were available they became the focus of low-melting eutectic of 107 °C. However, to yield a white “earth” when intensive study. Their vigorous reaction this route was abandoned because, at that heatedN at high temperature. This white with water and their spontaneous burn- time, electric current needed for electroly- earth was known as alumina and was an ing in air was impressive. In 1808, Davy sis was obtained only from batteries, which exceptionally stable material that it was announced further his belief that the plen- were tedious to construct, to operate, and considered a chemical element like gold, tiful compound alumina was the earth to maintain. He, therefore, considered the copper, and tin. When Alessandro Volta (oxide) of an undiscovered metal. Since chemical method devised by Wöhler. In then, scientists had been making efforts to 1854 he was able to prepare a small bar obtain this new metal. of the metal he prepared at the Javel plant near Paris to show at the meeting of the A visitor to Copenhagen French Academy of Sciences. He replaced potassium by sodium because he thought Davy never made any aluminum himself, but in the early 1820s the Danish scientist Hans Christian Oersted (1777-1851) (Fig. 2) succeeded in producing a tiny sample of the metal in the laboratory by reducing the aluminum chloride with potassium amal- gam. He had prepared aluminum chloride few years earlier for the first time by heat- Fig. 1: Humphry Davy (1778-1829) ing a mixture of alumina and charcoal in a stream of chlorine. Chlorine at that time in northern Italy discovered in 1800 that an electric current was generated when two metals were separated by an electrolyte, chemists in Europe immediately started to Fig. 4: Henri Sainte-Claire Deville (1818- study this new phenomenon and tried to 1881) make use of it. Napoleon Bonaparte as First Consul invited Volta to Paris in 1801 to that sodium was easier to prepare by reduc- demonstrate to him at the French National tion of the carbonate with coal at high Institute (the body that replaced the French temperature since there was no explosions Academy during the revolutionary period), Fig. 2 and 3: Hans Christian Oersted (1777- associated with the reaction as the case the principle of his discovery. Napoleon 1851) and Friedrich Wöhler (1800-1882) with potassium. This change resulted in a was impressed by the demonstration. He major improvement because he discovered gave Volta the Gold Medal of the Institute was a laboratory curiosity isolated few that the reaction product sodium chloride and ordered funds to the École Polytech- years earlier by Carl Wilhelm Scheele. formed a readily fusible double salt with nique to build a large battery for research. Friedrich Wöhler (1800- 1882) (Fig. 3) on excess aluminum chloride that acted as a The news of Volta’s discovery reached Eng- his return from Stockholm after finishing protective layer allowing the globules of land rapidly and a very large battery simi- his studies there with Jöns Jacob Berzelius, aluminum to coalesce forming large lumps lar to the one constructed in Paris was built stopped in Copenhagen in 1824 to visit of the metal which was not the case with at the newly founded Royal Institution in the University. He met Oersted there and previous method. London where Humphry Davy (1778-1829) learned about his experiments to iso- The great French chemist Jean-Baptiste (Fig. 1) succeeded in 1807 to isolate potas- late aluminum. Now in his laboratory in Dumas (1800-1884), a friend of Sainte-

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Claire Deville, got an audience with entists had been making efforts to obtain lite deposits there. He discovered that the emperor Napoleon III and convinced this new metal. A Danish whaler brought deposit was of limited size and rightly con-

him to subsidize the researches on alumi- a piece of the mineral cryolite, Na3AIF6, sidered that the French bauxite would be a num. Sainte-Claire Deville was also able found at Ivigtut, in south Greenland to more suitable raw material for an expand- to expose the bar at the Paris Exposition Copenhagen. In 1854, a process for the ing aluminum industry. in 1855 under the title The Silver of Clay recovery of alumina from cryolite was which was a great success. Sainte-Claire developed by Julius Thomsen (1826-1909) Deville was interested more in the scien- (Fig. 5) professor at the Technical Univer- tific aspects of the extraction of the metal sity of Copenhagen. The process involved than its commercial production. He there- heating the cryolite with limestone fol- fore suggested to his friend Paul Morin, a lowed by water leaching to extract sodium

mining engineer, to undertake the indus- aluminate formed, leaving behind CaF2 trialization of the project. in the residue. Aluminum hydroxide was then precipitated from the aluminate solu- Alumina from alum Fig. 7 and 8: John Percy (1817–1889) and tion by CO2 leaving sodium carbonate in solution to be recovered as a by-product Heinrich Rose (1795-1864) In 1856, Morin built a plant to produce and (Fig. 6). market the new metal at Glacière district in By the early 1860’s a large-scale soda and The aluminum ore known as bauxite Paris. He first obtained alumina by decom- alumina production based on cryolite was was discovered in 1821 by Pierre Berthier position of alum a hydrated aluminum sul- in operation and was one of the largest (1782-1861) (Fig. 9) professor at the School fate, but the inhabitants in the neighbor- industries in Denmark. The process was of Mines in Paris, while prospecting for

hood protested the emissions of SO2 from also transferred to few nearby countries iron ores in southern France. He called the plant. He had to move to Nanterre out- as well as in USA at the Pennsylvania Salt it “Terre d’alumine des Beaux” after the side Paris. Sainte-Claire Deville was also Company at Natrona near Pittsburgh. village of Les Beaux near Marseille where looking for a substitute for alum. However, in 1894 soda production from he made his discovery. The red color of cryolite ceased in Copenhagen because of the deposit had attracted his interest as Alumina from cryolite competition with the new Solvay process. a possible iron ore for the blast furnace In 1897 about 13,000 tons of the mineral in the district. However, it was found to

Since Davy’s announcement that alumina were mined, the major part of which was contain too much Al2O3 to be of value for was the earth of an undiscovered metal sci- delivered to the Pennsylvania Company, this purpose. The name was changed later but three years later, the process was also to beauxite and then to bauxite. Bauxite abandoned in USA. Thomsen is best known was shown by thermal analysis to contain

for developing the principle that the heat of a mixture of the hydroxides Al(OH)3 and formation is a measure of chemical affin- AlOOH and became the main raw material ity and for a four-volume work Thermo- for the modern aluminum industry. chemische Untersuchungen he published between 1882 and 1886.

Aluminum from cryolite

At the same time Sainte-Claire Deville was planning to produce aluminum on large Fig. 5: Julius Thomsen (1826-1909) scale by the reduction of alumina with sodium there were many attempts made to recover aluminum from cryolite. John Per- cy (1817–1889) (Fig. 7) at the Royal School of Mines in London in 1855 and simultane- Fig. 9 and 10: Pierre Berthier (1782-1861) ously Heinrich Rose in Berlin (1795-1864) and Louis Le Chatelier (1815-1873) (Fig. 8) reduced the mineral with sodium: Thermal method of treatment

Na3AlF6 + 3Na → Al + 6NaF When the need arose to produce alumina, The process was used for a short time but methods were developed to treat bauxite. was abandoned because of the attack of Aluminum can be solubilized readily from silica lining of furnaces by the fluorides. bauxite by acids but on adding an alkali to the solution a gelatinous basic salt, rather Alumina from bauxite than a crystalline hydroxide is precipitated. The gelatinous precipitate is difficult In the summer of 1856, Saint Claire Dev- to filter and wash. Furthermore, since iron Fig. 6: Production of alumina from cryolite ille went to Greenland to evaluate the cryo- and titanium are also partially dissolved in

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France, which included sodium carbonate needed for Le Chatelier’s process to produce alumina. Dumas who was on the Board of Directors of this company wel- comed the idea that the metal be produced at Salindre and Morin take charge of its marketing. Between 1860 and 1885, Merle was the only producer of aluminum in the world. When he died suddenly in 1877 at the age of 52, he was replaced by Alfred Pechiney (1833-1916) (Fig. 13) whose name was given to the company in 1971 when it was enlarged after a number of fusions with other companies. Fig. 15: Preparation of the double chloride of sodium and aluminum

W Preparation of metallic sodium by heating a mixture of calcined sodium carbonate, limestone, and coal in a retort (Fig. 16).

Fig. 11: Le Chatelier thermal method for alumina recovery from bauxite acid, the precipitate will be contaminated, Fig. 12 and 13: Henry Merle (1825-1877) creating a separation problem. As a result, and Alfred Pechiney(1833-1916) the acid-leaching route was never used to prepare Al2O3. The process at Salindre involved the fol- Sainte-Claire Deville proposed to his lowing steps: friend Louis Le Chatelier (1815-1873, not to W Preparation of alumina from bauxite by be confused with his son the chemist Henri Le Chatelier process (Fig. 14). Le Chatelier (1850-1936) best known for W Preparation of the double chloride of the thermodynamic principle which bears sodium and aluminum, AlCl3·NaCl, by his name) (Fig. 10), the Chief Inspector of reacting a mixture of Al2O3, NaCl, and Mines in France to develop a process for coal tar with gaseous chloride in an iron the recovery of alumina from bauxite. The retort (Fig. 15). Fig. 16: Preparation of metallic sodium process invented involved heating bauxite with sodium carbonate at 1000 °C to form W Production of metallic aluminum sodium aluminate, which is then leached by reacting the double chloride with with water. Aluminum hydroxide is then metallic sodium in a reverberatory fur- precipitated from this solution by bubbling nace (Fig. 17).

CO2 gas generated during the calcination step (Fig. 11). In 1859, the Nanterre plant produced 500 kg of aluminum using Le Chatelier’s alumina. In the same year, Sainte-Claire Deville wrote down his experience in a book he published under the title De l’aluminium, ses propriétés, sa fabrication, ses applications. But, the price of the metal was quite high nearly as high as silver - - it was sold for $12/pound while silver was $15/pound. Fig. 17: Production of metallic aluminum

Moving to southern France It became evident that this chemical route was expensive not only due to the numerous Negotiations were then started with Henry steps involved but also, the large amount of Merle (1825-1877) (Fig. 12) in Salindre in sodium needed - - at least 2.6 kg of sodium Southern France who was near the baux- were needed to produce one kg of alumi- ite deposits and who was at that time the Fig. 14: Preparation of alumina from bau- num. Means must, therefore, be found to major producer of inorganic chemicals in xite cut expenses.

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Production of sodium still too high because NaOH must first be Saint Petersburg in Russia by replacing CO2 produced from sodium carbonate by reac- by finely divided aluminum hydroxide on The production of sodium was a major cost tion with calcium hydroxide. The solution which precipitation took place by vigorous item in the production of aluminum. The must then be concentrated by evaporation process used was inefficient since only one then melted. third of the theoretical yield was obtained. In 1886, Hamilton Y. Castner (1859-1899) Aluminum Bronze (Fig. 18) a young graduate of Columbia University in New York produced sodium At the same time Deville was producing by using sodium hydroxide instead of sodi- metallic aluminum there was the produc- um carbonate: tion of aluminum-copper alloy known as aluminum bronze that had the appearance

6NaOH + 2C → 2Na2CO3 + 3H2 + 2Na of gold and was used in making tableware and was competing with the metal. Eugene Hutchinson Cowles (1855-1892) and his brother Alfred Cowles (1858-1929) established in 1885 at Cleveland, Ohio the first electric smelting plant using the electric resistance furnace which they invented (Fig. 19). Bauxite, charcoal, and copper were placed in the furnace; when the current turned on, resistance to the passage of the current offered by the charge generated heat which effected reduction of the alumina by the carbon. The liberated aluminum immediately combined with Fig. 18: Hamilton Y. Castner (1859-1899) the molten metal present to form an alloy. This collected at the bottom of the fur-

The cost of production was reduced but not nace and was tapped out at the end of the Fig. 21: Precipitation of Al(OH)3 by seeding enough. In 1891, he proposed the electroly- operation which lasted for about one hour. sis of molten NaOH in a specially designed Alloys containing 15-40% aluminum were cell. The process was efficient and a pure usually produced. It should be noted that product was obtained. But, the price was if copper were not present then aluminum carbide would be formed. Current was supplied from a dynamo. They achieved commercial success and few years later they established a plant at Stoke-on-Trent in England. For many years the aluminum bronze made by the Cowles were sold at Fig. 22: An original reactor for seeding of $5/pound of contained aluminum, a price aluminum hydroxide much lower than pure aluminum.

Alumina from bauxite by Bayer process

Le Chatelier process was modified by Karl Josef Bayer (1847-1904) (Fig. 20) in 1888 in

Fig. 19: Cowles’ electric resistance furnace for producing aluminum bronze Top: a perspective view; middle: a longitudinal section; bottom: a transverse section. N is a removable fire-clay cover, P is the charge of ore and granular charcoal, O is a packing of fire charcoal, and O‘ is a layer of granular charcoal covering the charge, n is Fig. 23: An electron micrograph of crystal- a gas vent, M and M‘ are the electrodes. Fig. 20: Karl Josef Bayer (1847-1904) line aluminum hydroxide

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agitation (Fig. 21). The new process was Aluminum could not be obtained by referred to as seeding and an original seed- electrolyzing an aqueous solution of alu- ing reactor is shown in Fig. 22. Crystalline minum salts and all efforts were directed

Al(OH)3 is shown in Fig. 23. towards fused salts making use of Kilani’s In 1892, Bayer modified the process fur- observation. Two scientists were working ther by introducing a pressure leaching on the electrolytic production of alumi- step which transformed the process into a num. They were born in the same year, fully hydrometallurgical process (Fig. 24). died in the same year, and succeeded in The process became known as the Bayer process. It received immediate success and Fig. 25: An original autoclave is used today in practically the same way as described in the original patents. An origi- concentrated nitric acid. This cell has an nal autoclave about one cubic used by Bayer output of about 1.9 V and a good current is shown in Fig. 25. capacity. Assembling enough of these cells to provide adequate electrical energy for aluminum production was a large under- taking. He had to build a furnace capable of producing high temperature. Still he was unable to melt some of the fluoride salts he tried, for example, calcium fluoride (m.p. 1360 °C), aluminum fluoride (m.p.1291 °C), Fig. 26: Martin Kiliani (1858-1895) and magnesium fluoride (m.p. 1266 C). Potassium and sodium fluorides melted their research on obtaining aluminum in in the furnace but did not dissolve useful the same year. These were Charles Martin amounts of aluminum oxide. Hall (1863-1914) (Fig. 27) and Paul Louis In 1886 Hall then experimented with syn- Heroult (1863-1914) (Fig. 28). thetic cryolite. He found that he could melt it (m.p. 1000 °C), and he showed that it was a good solvent for alumina. He used graphite rod electrodes, dipping them into a solution of alumina in molten cryolite in a clay crucible. When he let the current pass for a while then poured the melt into a pan he found only a greyish deposit on the nega-

Fig. 27 and 28: Charles Martin Hall (1863- Fig. 24: Bayer process for recovering alu- 1914) and Paul Louis Heroult (1863-1914) mina from bauxite Charles Martin Hall Incidentally the Bayer process was origi- nally invented in a chemical plant in Russia Hall took his chemistry course at Oberlin for the preparation of aluminum hydrox- College in Ohio, where Frank Fanning Jew- ide for mordanting textiles before dyeing. ett (1844-1926) lectured. Jewett displayed a sample of the metal that he acquired Fig. 29: Potline of early Hall cells in Pittsburgh in Electrolytic production of when he was studying from 1873 to 1875, 1890 aluminum at the University of Göttingen in Germany under Friedrich Wöhler. He predicted the In 1808 the German chemist Martin Kil- fortune that awaited the person who could iani (1858-1895) (Fig. 26) discovered that win this metal from its ore. Under Profes- a cryolite sample had an exceptionally low sor Jewett’s guidance and encouragement, melting point and when analyzed it was Hall worked on aluminum chemistry in found to contain a small amount of Al2O3 Jewett’s laboratory and at home when he as impurity [melting point of pure cryolite graduated in 1885. is 1009 °C]. Thus, he concluded that Al2O3 To obtain electricity in the 1880s for elec- decreases the melting point of cryolite. trolysis experiments in a small college This information was immediately utilized town, one had to construct batteries con- by those working on aluminum research sisting of a zinc electrode in a dilute sulfu- to propose cryolite as molten salt solvent ric acid surrounding a porous ceramic cup Fig. 30: Potline of early Hall cells in Pittsburgh in 1914 for Al2O3. which contains a carbon-rod electrode in

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tive electrode. After several repetitions, trométallurgique Francaise to build a new, new one. At the beginning of the 20th cen- Hall realized that this deposit was prob- larger capacity plant, in La Praz in the tury Carl Wilhelm Søderberg (1876-1955) ably elemental silicon originating from Maurienne Valley. (Fig. 34) invented the self-baking electrode the silicates of the crucible. He then used a which bears his name for the steel industry graphite crucible to serve as a liner for the when he was in Elektrokemisk Company clay crucible. When the electric current ran Norway’s largest chemical and metallurgi- for several hours and the he cooled the melt cal enterprise. The company attempted to he found several small silvery globules. develop a process for the direct production In 1888, Hall was using electricity obtained of steel from iron ore in an electric furnace from new steam-engine-driven Westing- but during World War I it was difficult to house dynamos, producing the first ingots obtain pre-baked electrodes. Søderberg of aluminum on a pilot scale. Indeed, suggested that instead of a multiplicity of development of such dynamos was a criti- pre-baked electrodes only one electrode cal contribution to the commercialization was to be employed per furnace. of electrometallurgy in the last decade of Such electrode consisted of a cylindrical the 19th century. A group of investors, metal casing extending from the cell to a organized in 1888, provided the financial platform located directly above the cell. backing for Hall while he worked at the Fig. 31: Héroult pot with four electrodes; This casing is filled with the carbonaceous Pittsburgh Reduction Company, the pred- his first attempt to lower the current den- mixture constituting the electrode and ecessor of Alcoa, Within two years, Hall sity in 1892 serves as a mould to hold and support the and his partners were producing alumi- carbon mix. In the lower part of the casing num metal on a commercial scale. Figs. 30 the electrode mix at the lower end is gradu- and 31 show the first units used by Hall. ally baked by the heat from the furnace as well as by the current passing through the Paul Louis Heroult casing and through the carbon of the electrode (where it has baked sufficiently to Heroult acquired accidentally the book become electrically conducting). In 1919 De l’aluminium, ses propriétés, sa fabrica- successful operation was achieved and the tion, ses applications published by Henri Søderberg electrode began to be used com- Sainte-Claire Deville in Paris in 1859 and mercially in the iron and steel industry. was fascinated by the new metal described In 1920-21 preliminary experiments were in the book. By using the electric furnace of Fig. 32: Pot with six cylindrical anodes conducted to apply this technology to the his design he succeeded in producing alu- installed by Héroult at the La Praz Plant in aluminum industry in Fiskaa Verk. In minum. He applied for a patent on April 23, 1893 1923 small scale installations were adopt- 1886; he was only 23 years old. ed in Germany, France, Switzerland, and To bring his process from the laboratory to The production of aluminum from alumi- the United States (Alcoa’s Badin plant in the commercial scale Heroult met Alfred na dissolved in cryolite with carbon anodes North Carolina). Starting in 1926 adop- Pechiney manager of Produits Chimiques can be represented as follows: tion became world wide and the Søder- d’Alais at Salindres the most important Cathodic reaction: Al3+ + 3e– → Al berg electrodes displacing the pre-baked chemical plant in southern France. How- Anodic reaction: O2– + C → CO + 2e– electrodes. An early version of the Soder-

ever, Pechiney disappointed him by sug- Overall reaction: Al2O3 + 3C → 2Al + 3CO berg electrode in aluminum production is gesting making aluminum bronze. Héroult shown in Fig. 35. then contacted a Swiss company operating Søderberg electrode In 1931 the rectangular electrode with a metallurgical plant at Neuhausen, on the capacity of 22 000 amperes was intro- banks of the Rhine. They agreed to create a Since the carbon anodes in the electrolytic duced in France. Søderberg electrodes Swiss metallurgical company with Héroult process were consumed during the reac- were also installed in the copper, nickel, as technical director. tion they were continuously replaced by and ferroalloy industries. However, in the They founded the Société Électrométallur- 1980s some aluminum plants in China and gique Francaise in 1888 for producing alu- in Western countries returned to the pre- minum. The new plant, located in Froges in baked electrodes in spite of their cost pri- the Isere, had difficult beginnings. The cost marily to abate pollution in the vicinity of of a kilo of aluminum, while three times the pots, while in Russia the working con- less than the cost of chemically obtained ditions were improved and the pre-baked aluminum at the Salindres plant, was still electrodes were maintained. too high. In 1892, Héroult built more pots, with four (Fig. 32) and then six anodes (Fig. Aluminum and copper 33). By lining the pot with a layer of carbon and pitch, reducing the electric voltage to 6, Aluminum was the chief competitor to then to 5 volts, costs began to drop. Héroult Fig. 33: Carl Wilhelm Søderberg (1876- copper with respect to electrical conduc- was then able to persuade the Société Elec- 1955) tivity. Although aluminum has conductiv-

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Fig. 36: Production of aluminum versus copper

Aluminum and boron Fig. 34: An early version of the Søderberg electrode in aluminum production Aluminum is a typical metal composed Copper Aluminum of crystals made of closely packed atoms Electrical conductivity, at 20 °C, S.m−1 5.98 x 107 3.5 x 107 whose outer electrons are so loosely held that they are free to move throughout the Specific gravity 8.89 2.699 crystal lattice. A typical metal has the fol- Tab. 1: Comparison of copper and aluminum lowing properties: W An electronic structure similar to that of the inert gases with one, two, or three electrons in the outermost shell. W A single valency, i.e., it loses its outermost electrons in a single step. W It is reactive, i.e., reacts readily with water and oxygen. The driving force for this reactivity is the inclination to achieve maximum stability by attaining the electronic structure of an inert gas. A reactive metal such as aluminum or magnesium may be used as material of Fig. 35: Price of aluminum versus copper construction because of the protective oxide film that is formed rapidly on its ity less than copper but its lightness was an below boron and above gallium (Fig. 38). surface. advantage over copper especially in cables However, its properties are different from W It forms only colorless compounds. transmitting electricity (Table 1). The price both boron and gallium but more similar of aluminum started higher than copper to the alkali and alkaline earth metals. On the other hand boron is a metalloid: in but in 1960s it became cheaper while its Moving aluminum to join the other typical the elemental form its atoms are bonded production started lower than copper but metals group with similar properties and together by covalent bonds (Fig. 39). It has surpassed it also in 1960s (Figs. 36 and electronic configuration will allow divid- an intermediate properties between metals 37). ing the elements into metals, nonmetals, and nonmetals, i,e., looks like a metal but and metalloids (Fig. 38). Metals are divided is fragile like a nonmetal.

Aluminum in the Periodic Table further into typical, less typical, transition, Boron hydroxide, B(OH)3, and aluminum

and inner transition. The diagonal similar- hydroxide, Al(OH)3, are fundamentally In the Periodic Table found in most text- ity between beryllium and aluminum is different. Boron hydroxide is a weak acid books of chemistry, aluminum is situated well marked. known also as boric acid, H3BO3, which

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crust is 1.5 x 10-3% while aluminum is the third most abundant element with a relative abundance of 8.13% (after oxygen and silicon).

Aluminum and scandium

The chemistry of scandium is very similar to that of aluminum. Both metals are trivalent and both form colorless com- Fig. 37: Periodic Table found in most chemistry textbooks pounds. The hydroxides of both metals are amphoteric.

Diagonal similarity

Putting aluminum next to magnesium and above scandium has the advantage of better visualizing the diagonal similarities between Li-Mg, Be-Al, and B-Si (Fig. 39): W Lithium is more similar to magnesium than to the members of the alkali metals. It forms insoluble carbonate like magnesium. Fig. 38: A Periodic Table divided in different groups and shows the diagonal similarity W Beryllium is more similar to aluminum than to alkaline earth metals. It dissolves in alkalis to form borates but yet there are marked differences between forms covalent bond chloride similar

is insoluble in acids. Aluminum hydrox- both metals: to AlCl3. ide, on the other hand, is an amphoteric W While aluminum oxidizes so rapidly W Boron is more similar to silicon than hydroxide - - it dissolves in acids and in that it soon forms a non-porous protec- to aluminum. It is a metalloid like sili- alkalis. Boron hydride is volatile, flamma- tive layer, gallium does not. con while aluminum is a typical metal. ble, and readily hydroylzed while alumi- W Gallium can be electrodeposited from Boron and silicon hydrides are volatile, num forms solid hydrides. aqueous solution, while aluminun flammable, readily hydroylzed. Alu- cannot. minum forms solid hydrides. Boron Aluminum and gallium W Al(OH)3 does not dissolve in ammo- oxide, B2O3, and SiO2 are similar in

nium hydroxide solution, but Ga(OH)3, acidic nature, can dissolve oxides form- Gallium is a less-typical metal, i.e., it dif- does dissolve. ing glasses. fers from a typical metal in that it does not W Gallium is precipitated from aqueous Suggested Readings have an electronic structure similar to the solution by H2S as a sulfide; aluminum inert gases. Its outermost shell contains does not. - J.D. Edwards, F.C. Frary, and Z. Jeffries, Alu- three electrons and the next inner shell W Aluminum forms carbides, gallium minum and Its Production, McGraw- Hill, New York 1930 contains 18 instead of 8 electrons as in does not. - F. Habashi, Aluminum. History & Metallurgy, the inert gas structure. Although gallium W Aluminum carbide, Al C is similar to Métallurgie Extractive Québec, Québec City, 4 3 Canada 2008. Distribute by Laval University occurs in bauxite together with aluminum the carbides of the first three groups, Bookstore, www.zone.ul.ca - F. Habashi, Textbook of Hydrometallurgy, being ionic colorless compound con- second edition, Métallurgie Extractive taining the C 2- anion that decomposes Québec, Québec City, Canada 1999. Dis- 2 tribute by Laval University Bookstore, www. in water. However, it liberates meth- zone.ul.ca ane instead of acetylene like the other - F. Habashi, “Periodic Table and the Metallur- gist,” Metall 62 (7–8), 454–460 (2008) members of the group: Al C + 12H O - F. Habashi, Readings in Historical Metal- 4 3 2 lurgy, Volume 1. Changing Technology in → 4Al(OH)3 + 3CH4 Extractive Metallurgy, Métallurgie Extrac- W Gallium forms a gaseous hydride, tive Québec, Québec City, Canada 2006. Dis- tribute by Laval University Bookstore, www. Ga2H6, while aluminum forms a white zone.ul.ca - J. Lanthony, L’Aluminium et les Alliages solid polymer hydride, (AlH3)x. Légers. Presse Universitaires de France, Paris W Historically, aluminum oxide was con- 1968 - P. Morel, editor, Histoire Technique de la Pro- sidered an earth like the rare earths and duction d’Aluminium, Presse Universitaire it fits with the scandium group. de Grenoble, Grenoble 1992 W Mendeleev successfully predicted the properties of scandium before it was dis- (1) Fathi Habashi, Department of Mining, covered by linking it with aluminum. Metallurgical, and Materials Engi- W Gallium is a typical dispersed element neering, Laval University, Quebec City, Fig. 39: Structure of elemental boron whose relative abundance in the Earth’s Canada

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