Borax (a mixture of Na₂B₄O₇.4H₂O and Na₂B₄O₇.10H₂O) was known for thousands of years. In Tibet it was known by the Sanskrit name of tincal. Borax glazes were used in China in 300 AD, and the writings of the Arabic alchemist Geber (Figure 1) appear to mention it in 700 AD. However, it is known that Marco Polo brought some borax glazes back to Italy in the 13th century. In 1600 Agricola (Figure 2) in his treatise De Re Metallica reported the use of borax as a flux in metallurgy.

Figure 1: A drawing of the father of chemistry Abu Musa Jābir ibn Hayyān al azdi known by Geber; the Latinized form of Jabir (721 - 815). Geber was a chemist and alchemist, astronomer and astrologer, engineer, geologist, philosopher, physicist, and pharmacist and physician.

Figure 2: A painting of German author Georg Bauer (1494 - 1555), whose pen-name was the Latinized Georgius Agricola, was most probably the first person to be environmentally conscious.

Boron was not recognized as an element until its isolation by Sir Humphry Davy (Figure 3), Joseph Louis Gay-Lussac (Figure 4) and Louis Jacques Thénard (Figure 5) in 1808 through the reaction of boric acid and potassium. Davy called the element boracium. Jöns Jakob Berzelius (Figure 6) identified boron as an element in 1824.

Figure 3: British chemist and inventor Sir Humphry Davy FRS (1778 - 1829).

Figure 4: French chemist and physicist Joseph Louis Gay-Lussac (1778 –1850).

Figure 5: French chemist Louis Jacques Thénard (1777 - 1857).

Figure 6: Swedish chemist Friherre Jöns Jacob Berzelius (1779 - 1848).

Ancient Greeks and Romans used aluminum salts as dyeing mordants and as astringents for dressing wounds; alum (KAl(SO₄)₂.12H₂O) is still used as a styptic (an antihaemorrhagic agent). In 1808, Sir Humphry Davy (Figure 3) identified the existence of a metal base of alum, which he at first termed alumium and later aluminum.

The metal was first produced in 1825 (in an impure form) by Hans Christian Ørsted (Figure 7) by the reaction of anhydrous aluminum chloride with potassium amalgam. Friedrich Wöhler (Figure 8) repeated the experiments of Ørsted but suggested that Ørsted had only isolated potassium. By the use of potassium, Equation 1, he is credited with isolating aluminum in 1827. While Wöhler is generally credited with isolating aluminum, Ørsted should also be given credit.

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Figure 7: Danish physicist and chemist Hans Christian Ørsted (1777 - 1851).

Figure 8: German chemist Friedrich Wöhler (1800 - 1882) also known for his synthesis of urea and, thus, the founding of the field of natural products synthesis.

In 1846 Henri Deville (Figure 9) improved Wöhler's method, and described his improvements in particular the use of sodium in place of the expensive potassium

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Figure 9: French chemist Henri Etienne Sainte-Claire Deville (1818 - 1881).

The element gallium was predicted, as eka-aluminum, by Mendeleev (Figure 10) in 1870, and subsequently discovered by Lecoq de Boisbaudran (Figure 11) in 1875; in fact de Boisbaudran had been searching for the missing element for some years, based on his own independent theory. The first experimental indication of gallium came with the observation of two new violet lines in the spark spectrum of a sample deposited on zinc. Within a month of these initial results de Boisbaudran had isolated 1 g of the metal starting from several hundred kilograms of crude zinc blende ore. The new element was named in honor of France (Latin Gallia), and the striking similarity of its physical and chemical properties to those predicted by Mendeleev did much to establish the general acceptance of the periodic Law; indeed, when de Boisbaudran first stated that the density of Ga was 4.7 g cm^-3 rather than the predicted 5.9 g/cm³, Mendeleev wrote to him suggesting that he redetermine the value (the correct value is 5.904 g/cm³).

Figure 10: Russian chemist and inventor Dmitri Ivanovich Mendeleev (1834 – 1907).

Figure 11: French chemist Paul Émile (François) Lecoq de Boisbaudran (1838 – 1912).

While testing ores from the mines around Freiberg, Saxony, Ferdinand Reich (Figure 12) and Hieronymous Theodor Richter (Figure 13) when they dissolved the minerals pyrite, arsenopyrite, galena and sphalerite in hydrochloric acid, and since it was known that ores from that region contained thallium they searched for the green emission lines by spectroscopy. Although the green lines were absent, a blue line was present in the spectrum. As no element was known with a bright blue emission they concluded that a new element was present in the minerals. They named the element with the blue spectral line indium. Richter went on to isolate the metal in 1864.

Figure 12: German chemist Ferdinand Reich (1799 - 1882).

Figure 13: German chemist Hieronymus Theodor Richter (1824 - 1898).

After the publication of their improved method of flame spectroscopy by Robert Bunsen (Figure 14) and Gustav Kirchhoff (Figure 15) this method became an accepted method to determine the composition of minerals and chemical products. Two chemists, William Crookes (Figure 16) and Claude-Auguste Lamy, both started to use the new method and independently employed it in their discovery of thallium.

Figure 14: German chemist Robert Wilhelm Eberhard Bunsen (1811 - 1899).

Figure 15: German physicist Gustav Robert Kirchhoff (1824 - 1887).

Figure 16: English chemist and physicist Sir William Crookes, FRS (1832 –1919) attended the Royal College of Chemistry (now Imperial College) in London.

Crookes was making spectroscopic determinations on selenium compounds deposited in the lead chamber of a sulfuric acid production plant near Tilkerode in the Harz mountains. Using a similar spectrometer to Crookes', Lamy was determining the composition of a selenium-containing substance that was deposited during the production of sulfuric acid from pyrite. Using spectroscopy both researchers both observed a new green line the atomic absorption spectrum and assigned it to a new element. Both set out to isolate the new element. Fortunately for Lamy, he had received his material in larger quantities and thus he was able to isolate sufficient quantities of thallium to determine the properties of several compounds and prepare a small ingot of metallic thallium. At the same time Crookes was able to isolate small quantities of elemental thallium and determine the properties of a few compounds. The claim by both scientists resulted in significant controversy during 1862 and 1863; interestingly this ended when Crookes was elected Fellow of the Royal Society in June 1863.

Due to aluminum’s position as the most abundant metallic element in the Earth's crust (7.5 - 8.1%) and its enormous industrial importance warrants detailed discussion of its industrial production. Aluminum only appears in its elemental form in nature in oxygen-deficient environments such as volcanic mud. Ordinarily, it is found in a variety of oxide minerals.

In comparison to other metals aluminum is difficult to extract from its ores. Unlike iron, aluminum oxides cannot be reduced by carbon, and so purification is only possible on an economic scale using electrolysis. Prior to electrolysis purified aluminum oxide is obtained by refining bauxite in the process of developed by Karl Bayer (Figure 17).

Figure 17: Austrian chemist Karl Josef Bayer (1847 –1904) whose father, Friedrich, founded the Bayer chemical and pharmaceutical company.

Bauxite, the most important ore of aluminum, contains only 30-50% alumina, Al₂O₃, the rest being a mixture of silica, iron oxide, and titanium dioxide. Thus, the alumina must be purified before it can be used as the oxide or refined into aluminum metal. In the Bayer process, bauxite is digested in hot (175 °C) sodium hydroxide (NaOH) solution (Figure 18). This converts the alumina to aluminum hydroxide, Al(OH)₃, which dissolves in the hydroxide solution.

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The other components do not dissolve and are filtered off (Figure 18). The hydroxide solution is cooled, and the dissolved aluminum hydroxide precipitates, which when heated to 1050 °C is calcined into alumina.

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Figure 18: Schematic representation of the Bayer process. Copyright: Andrew Perchard, Alcan Aluminium UK and courtesy of Glasgow University Archives (2007).

Once a pure alumina is formed, it is dissolved in molten cryolite (Na₃AlF₆) and reduced to the pure metal at elevated temperatures (950 - 980 °C) using the Hall-Héroult process, developed independently Charles Hall (Figure 19) and Paul Héroult (Figure 20).

Figure 19: American inventor and engineer Charles Martin Hall (1863 – 1914).

Figure 20: French scientist Paul (Louis-Toussaint) Héroult (1863 – 1914).

Both of the electrodes used in the electrolysis of aluminum oxide are carbon (Figure 21). The reaction at the cathode involves the reduction of the Al³⁺, Equation 5. The aluminum metal then sinks to the bottom and is tapped off, where it is usually cast into large blocks called aluminum billets.

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Figure 21: Schematic of the Hall-Héroult cell.

At the anode oxygen is formed, Equation 6, where it reacts with the carbon anode is then oxidized to carbon dioxide, Equation 7. The anodes must be replaced regularly, since they are consumed. While the cathodes are not oxidized they do erode due to electrochemical processes and metal movement.

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Although the Hall-Héroult process consumes a lot of energy, alternative processes have always found to be less economically and ecologically viable.