Interesting Facts

Learn more about PIDC's inorganic materials using this convenient Periodic Table page.

Rare Earth metals & compounds

Cerium was first discovered in 1803 and is the most abundant of the rare earth elements. Deposits of the most common cerium sources are monazite, which exists in India, Brazil, Australia and Africa, and bastnasite found in China and North America, which are typically between 30-50% Cerium. Elemental Cerium is a soft, silvery metal that is very reactive in air and will ignite with the scrape of a knife. Cerium exists in either of two oxidation states, Cerous (III) and Ceric (IV). Ceric salts such as Cerium Ammonium Nitrate, (NH₄)₂Ce(NO₃)₆, are usually yellow or orange while Cerous salts are typically white. Currently, the most commercially popular Cerium compounds are Cerous and Ceric Salts as well as Ceric Oxide.

Cerium metal is a prime component of Mischmetal, which is used in the manufacture of pyrophoric alloys (such as ignition flints for welding torches and lighters). The metal is also finding use as an additive to the walls of self-cleaning ovens as it helps prevent the collection of cooking residues. The oxide is very commonly used in glass applications as both a component and a decolorizing agent while it is also finding vast use as a polishing medium as well. The sulfate is used as a volumetric oxidizing agent in quantitative analysis. Cerium is also used in the production of television phosphors, auto-catalysts and petroleum refining.

Discovered in 1886, Dysprosium is named for the Greek word dysprositos, which means "hard to get". True to its name, Dysprosium was not isolated until 1950, sixty-four years after its discovery. Commercial sources of Dysprosium are bastnasite ore found in China and North America as well as the ionic clays found in Southern China, with the latter containing a greater percentage of the element at about 4-10%. Elemental Dysprosium exists as a silvery-white metal that is stable in air and soft enough to cut with a knife. Dysprosium is commonly available in its lustrous metal form as well as its powdered oxide form.

Dysprosium metal is used in permanent magnets for use in audio speakers and industrial applications as well as for magnetorestricitive alloys. The metal can also be combined with Vanadium and other rare earths to form an alloy used in laser manufacture. Dysprosium's thermal neutron absorption cross-section and high melting point make it ideal for combining with stainless steel in nuclear applications. Along with other small applications, Dysprosium oxide has found use in a nickel cement used for cooling nuclear reactor rods.

Erbium was first discovered in its oxide form in Ytterby, Sweden in 1842 but was not isolated in great purity until 1905. Commercial sources are monazite ore found in India, Brazil, Australia and Africa, bastnasite ore mined in China and North America and the ionic clays of Southern China, which has the highest Erbium content among the three, 2-5%. Erbium metal is lustrous and silvery white with a very soft and malleable form. Erbium metal oxidizes less quickly in air than other rare earth metals, though it is similar in most other respects. The oxide stands out amongst other rare earth oxides with its unique pale pink color. Erbium metals and oxides are commonly available in commercial markets.

Erbium metal has uses similar to those of other rare earth metals such as metallurgy and superconductors though special exclusive uses for the oxide exist by virtue of its distinct color. Because of the pastel pink color, due to its sharp absorption lines (common to rare earth oxides), Erbium Oxide is used widely as a coloring agent for glass and ceramics. The medical field has some use for Erbium in as a dopant for lasers used in surgery. The powdered oxide is also used in fiber optics and glass for its ultraviolet absorbing capabilities.

Europium was discovered in 1890 when suspicious emission lines were observed in a sample of Samarium and Gadolinium. Most credit its official discovery to Demarcay who isolated a pure sample in 1901. Being the most reactive of the rare earth elements, Europium is very difficult to isolate and is separated from monazite ore found in India, Brazil, Australia and Africa, bastnasite ore found in China and North America and the ionic clays of Southern China, all of which contain slight amounts of Europium, 0-1%. Difficulty in separation and rarity make Europium one of the most expensive rare earth elements, though it is used in many common consumer goods.

Europium metal readily oxidizes in air making it ideal for pyrophoric alloys, but because lighter, cheaper rare earth metals boast similar properties this market is sparse for Europium, which has few metal applications. Europium has found its greatest use as a phosphor activator and is widely used in europium-activated yttrium compounds to produce red color in television, computer monitor and LED displays. This application accounts for the vast majority of Europium consumption worldwide. Europium is also used to dope plastics in lasers.

Gadolinium was first isolated in 1880 and named for the Gadolinite ore that it was isolated from (the ore itself is named for Finish chemist Gadolin). Gadolinium is found in the monazite ores of India, Brazil, Australia and Africa, bastnasite ores of China and North America and is also refined from the ionic clays of Southern China, all of which contain about 0-5%. Gadolinium metal is similar to other rare earth metals aside from its unique Curie temperature, which lies at just above room temperature. The element also has the single highest thermal neutron capture cross-section of any known element at 49,000 barns and has found use in nuclear applications. Along with metal, the oxide form is also readily available on the chemical market.

Gadolinium metal is used to enhance iron, chromium and similar alloys to increase their resistance to oxidation at high temperatures. The metal is also an unusually good superconductor, which also finds its use in some special materials and alloys. Gadolinium Yttrium Garnets are used in microwave applications and other Gadolinium compounds are used in color television phosphors. In the medical realm, solutions of gadolinium compounds are used as intravenous contrasts to enhance images in patients undergoing MRI (magnetic resonance imaging).

Holmium was discovered in 1878 and named for Stockholm, the home city of its chemist discoverer. Holmium exists in monazite ore found in India, Brazil, Australia and Africa, bastnasite ore found in China and North America as well as ionic clays found in Southern China, which contains the most at about 2% Holmium. Elemental Holmium is a lustrous, ductile metal with unusual magnetic properties. Holmium has few large industrial applications but is commercially available in oxide and metal forms.

Holmium is used as to dope Yttrium-Aluminum Garnets used in laser surgery and is also used in to quench nuclear chain reactions in fission reactors. Holmium finds some use in alloy and phosphors production as well as in filters for UV Spectrometer calibration.

Holmium is also popular among lighting researchers and ceramics companies.

Lanthanum was discovered in an impure sample of cerium nitrate in 1839 and named for the Greek word lanthanein, which means "to lie hidden". Lanthanum exists in great amount in monazite ore found in India, Brazil, Australia and Africa, bastnasite ore of China and North America and can also be found in the ionic clays of Southern China. Each of the major sources contain about 20-30% Lanthanum by weight. Similar to Cerium, Lanthanum exists elementally as an extremely soft, luminous metal that is readily oxidized in air and water and reacts with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus and sulfur. Lanthanum is commercially available in metal, oxide and several salt forms.

Lanthanum metal is used in many applications similar to those of Cerium such as alloys and flints. The metal is also used in the fabrication of nodular cast iron. Lanthanum's favorable presence in fuel-cracking catalysts have made a market for the plentiful rare earth in the petroleum industry while it also finds use in the glass market as a dopant to increase resistance to alkali compounds. The most recent interest in Lanthanum has come from its use in Hydrogen Sponge Alloys, which are an important component of solid oxide fuel cells.

Lutetium was discovered in 1907 by three independent chemists in France, Germany and New Hampshire (USA) from a material that Marignac had separated and named "ytterbium". As one of the rarest of the rare earth elements, Lutetium is available in very short supply from bastnasite ore and Chinese ionic clay, which each contain less than 0.5% Lutetium by weight. Lutetium's abundance in any natural material correlates proportionally to that of Yttrium as the two share many elemental similarities. It is commercially available in its oxide and metal forms though few industrial applications exist.

Lutetium's rarity and difficult separation have hurt its chances with commercial success. Some applications exist in the lighting phosphor industry while others use Lutetium in cracking and polymerization catalysts. While there is research being done on Lutetium's use in specialty alloys, no large markets currently exist for the heavy lanthanide.

Mischmetal, being primarily Cerium and Lanthanum, is popular in pyrophoric alloys used in flints and lighters. Mischmetal is also used in many specialty alloys. Mixed rare earth oxide is often used as a polishing component. Mixed Rare earth salts and oxides are popular in the auto catalyst and electronics industries. In general, mixed rare earth products are an economical option in applications that call simply for material with characteristics shared by the lighter rare earth elements such as reactivity or crystal structure. It is also common for companies to purchase rare earth salts and oxides with the intention of handling their separation themselves.

Mixtures of the several rare earth elements refined into metals, oxides and salts are commercially popular and have many applications. The mixtures are typically made from the monazite ore of India, Brazil, Australia and Africa or bastnasite ore of China and North America. The elemental form of mixed rare earth is known as Mischmetal and has lustrous and ductile characteristics like those of its constituents. The other common forms; carbonate, oxide, chloride and fluoride, exist as white to brown/orange powders or crystal aggregates. The compositions of all mixed rare earth materials are typically that of the ore from which they were produced, often being primarily made of Cerium, Lanthanum, Praseodymium and Neodymium. These materials are usually more economical that other rare earth products because less separation is required.

Neodymium was discovered in 1885 by von Welsbach when he separated the element from a mix that was then known as Didymium. The sixtieth element is found in monazite ore of India, Brazil, Australia and Africa, bastnasite ore of China and North America as well as in the ionic clays of Southern China, with each source containing 0-20% Neodymium. Neodymium metal is one of the more reactive rare earth metals and will oxidize quickly when exposed to air. Neodymium compounds vary in color from blue to purple to red and give the lanthanide some unique commercial uses. Because of its presence in the various forms of rare earth containing ores and clays, Neodymium is popular in general lanthanide applications and can be used to weight the strength of the rare earth market as a whole. Neodymium is readily available in its metal and oxide forms as well as several salts including carbonate and nitrate.

Neodymium metal is used extensively to produce Nd-Fe-B magnets, which have energy densities as high as 27 to 35 million gauss oersteds. They are the most compact magnets commercially available. Neodymium compounds are extensively used in glasses and coatings for their unique colors and ultraviolet absorption abilities. Welding goggles are commonly darkened with didymium, a neodymium-containing compound, and neodymium alone is used to color glass delicate shades of red, blue, purple and gray. Neodymium's coloring characteristics are used in applications ranging from small artistic products to large mass-production. Neodymium is also used widely in electronic, auto catalyst and rubber catalyst applications.

Praseodymium was extracted from Didymium in 1885 and named for its green color (the Greek word prasios means "green") by von Welsbach. Praseodymium exists in moderately abundant amounts (1-5%) in monazite ore of India, Brazil, Australia and Africa, bastnasite ore found in China and North America as well as in the ionic clays of Southern China. Praseodymium metal is slightly less reactive in air than most rare earth metals. Similar to Cerium, Praseodymium exists in the (III) oxidation state as well as in the (IV) state though, unlike Cerium, its oxide is generally a mix of the two to form Pr₆O₁₁. Praseodymium compounds exhibit an array of different colors from jet black to lime green. Like most rare earth elements Praseodymium is commercially available in its metal, oxide and carbonate forms.

Praseodymium is used in applications common to rare earth elements. The metal is a modest constituent of Mischmetal, which is an alloy of rare earth metals, primarily cerium, lanthanum, praseodymium and neodymium. Mischmetal is used in heat-conducting and pyrophoric alloys. Other compounds of Praseodymium are used for their unique colors. Praseodymium is mixed in glass along with other compounds to produce a bright but smooth yellow color while Didymium, a mix of Praseodymium and Neodymium (among others) is used to color the glass in welding goggles. Praseodymium also finds some use in lighting applications (like many rare earth elements).

Samarium was discovered in the mineral samarskite in 1879 by Lecoq de Boisbaudran when he observed some peculiarly sharp absorption lines. Only recently has Samarium been isolated in pure form. Samarium exists in monazite ore found in India, Brazil, Australia and Africa, bastnasite ore of China and North America as well as the ionic clays of Southern China, each containing about 1-5% Samarium. The bright silver metal is soft and ductile and reacts somewhat slower in air than most rare earth metals. Samarium is commercially available in its metal and oxide forms.

Samarium is popular in Samarium-Cobalt magnets, which have the highest resistance to demagnetization of any known material and intrinsic coercive force as high as 2200 kA/m. Glass is often made to contain Samarium to absorb infrared light and Calcium Fluoride crystals in laser and masers are also doped with Samarium to enhance optical performance. Compounds of the metal act as sensitizers for phosphors excited in the infrared. The oxide exhibits catalytic properties in the dehydration and dehydrogenation of ethyl alcohol. Samarium is also used as a neutron absorber in nuclear applications.

Terbium was discovered in 1843 by Mosander and named for the Swedish city of its origin. Commercial sources of Terbium are monazite ore found in India, Brazil, Australia and Africa, bastnasite ore of China and North America as well as the ionic clays of Southern China, which yields the most Terbium at 0.5-1.5%. Elemental Terbium is a soft, silvery metal that reacts in air slower than most rare earth metals. Aside from its metal form, Terbium is also commercially available in its oxide form, which is a brown or dark red powder.

Terbium has many small applications, but no large-scale industrial uses as of yet. It is used as a dopant in calcium fluoride, calcium tungstate, and strontium molybdate, which are used in solid-state devices. The oxide has potential to be used as an activator in green phosphors for television tubes. Sodium terbium borate is used as a laser material and emits coherent light at 0.546 um. Also, Terbium can be used with ZrO₂ as a crystal stabilizer in high temperature fuel cells.

Thulium was discovered in 1879 by the Swedish chemist Theodor Cleve and has not been available in a pure elemental form until very recently. Thulium is the rarest of the rare earth elements and is found in small supply (<0.6%) amongst other lanthanides in monazite ore found in India, Brazil, Australia and Africa, bastnasite ore found in China and North America as well as in the ionic clays of Southern China. The metal is soft, silvery and does not react as quickly with air as other rare earth metals, though it will oxidize. Despite its rarity, Thulium is commercially available in its metal and oxide forms.

Due to its rarity and high-cost little is known about the commercial potential of Thulium. Like all lanthanides, Thulium metal is used in limited specialty alloy applications and may be useful because of its nuclear, conductive and magnetic properties. Thulium 169 that has been bombarded in nuclear reactors may be used as a radiation source in portable x-ray machines. Another possible application is use in ceramic magnets (ferrites) for use in microwave devices.

Ytterbium was discovered in 1878 in what was then known as Erbia. Ytterbium is produced commercially from monazite ore found in India, Brazil, Australia and Africa, bastnasite ore from China and North America as well as from the ionic clays of Southern China, which contains the highest concentration at 2-4%. Elemental Ytterbium is a soft, silvery metal that is quite stable, though will oxidize if left exposed to air or water for very long. The metal exhibits typical metallic conductive properties, but when brought to high pressure (>16,000 atm) at room temperature the metal becomes a semiconductor. Ytterbium is commercially available in its oxide and metal forms.

Few industrial applications exist for Ytterbium probably due to its cost and rarity. Stainless steel has shown increased grain refinement, strength and other mechanical attributes when combined with small amounts of Ytterbium. One isotope is believed to be useful in portable x-ray devices for use when electricity is unavailable (similar to Thulium). Ytterbium is used in limited phosphor applications as well as in certain kinds of specialized catalysts.

Yttria, an oxide ore that would later be split into Yttrium, Terbium and Erbium, was discovered in 1794 by the Finish chemist Gadolin. When the ore was split in 1843, the name Yttrium was given to the simplest of the resulting elements. Though Yttrium is neither a lanthanide nor an actinide, it is considered a rare earth element because of its similarity and natural proximity to the lanthanides. Yttrium is present in monazite ore found in India, Brazil, Australia and Africa, bastnasite ore from China and North America and, in greater abundance, in the ionic clays of Southern China. Elemental Yttrium is a soft, luminous metal and is relatively stable in air, though shavings and small pieces of the metal have been known to ignite at 400^oC. Yttrium oxide is the far more popular commercial form of the element, though both it and the metal are readily available.

Yttrium Oxide has found many uses in industrial and commercial products. Yttria is commonly mixed with Europium to form (Y, Eu)VO₄ and (Y, Eu)₂O₃ phosphors, which produce the red color in television tubes. Several different Yttrium garnets also call for the rare earth. Yttrium-Aluminum garnet (with a hardness of 8.5) is used as a synthetic diamond for technical applications including lasers used in surgery and Yttrium-Iron garnets make useful microwave filters. Other uses may also exist as Yttrium Iron, Aluminum, and Gadolinium garnets, with formulas such as Y₃Fe₅O₁₂ and Y₃Al₅O₁₂, have interesting magnetic properties. Small amounts of Yttrium (0.1 to 0.2%) can be used to reduce the grain size in Chromium, Molybdenum, Zirconium, and Titanium, and to increase strength of Aluminum and Magnesium alloys. The metal can be used as a deoxidizer for vanadium and other nonferrous metals. Yttrium has also been explored as a nodulizer for producing nodular cast iron, in which the graphite forms compact nodules instead of the usual flakes increasing ductility. Adding Yttrium to glass lends shock resistance and low expansion characteristics, which make the element popular in glass and ceramic applications as well.

Other metals & compounds

Chrome is an inorganic compound consisting of the formula Cr2O3. Parisians, Pannetier and Binet, first prepared Cr2O3 in 1838 via a secret process. Nowadays, it is manufactured using the mineral chromite. Chromite is mined in Asia, Turkey, Cuba and South Africa. The conversion from chromite to chrome involves the oxidation to Na2Cr2O7, and is then reduced with carbon or sulfur. Chrome is commonly used as a metal polish known as green rouge. It is also used to make molds for firing bricks. Chromium Oxide is also used in the manufacturing of magnetic tapes.

Cobalt was first isolated by George Brandt in 1735. It is not found as native metals, but rather it is generally found in the form of ores. Cobalt tends to be produced as a by-product of nickel and copper mining activities. The main ores of cobalt are cobalite, erythrite, glaucodot, and skutterudite. Interestingly, cobalt has been detected in ancient ceramics. It was found in Egyptian sculptures, Persian jewelry and in China dating from the Tang dynasty, AD 618 - 907. John Livingood and Glenn Seaborg discovered cobalt-60 in 1938. This radioactive isotope is used as a radioactive tracer and cancer treatment agent. Cobalt-60 is also useful as a gamma ray source. It is used for the sterilization of medical supplies, industrial radiography, density measurements, and lastly, in tank fill switches. Cobalt is also used in the preparation of magnetic, wear-resistant, and high-strength alloys. Similar to its ancient use, cobalt is used in the production of inks, paints, and varnishes.

Gallium was discovered in 1875 spectroscopically by Boisbuadran. Sources of Gallium are diaspore, sphalerite, germanite, bauxite, and even coal, though only in trace amounts. Elemental Gallium is an extremely soft metal that is liquid at temperatures slightly higher than room temperature (29.76^oC). Similar to Mercury, though not known to be as toxic, Gallium is very shiny and readily alloys with other metals. Gallium has the longest liquid temperature range of any metal and low vapor pressure even at high temperatures. Commercially, Gallium is available in oxide form.

Gallium can be used to wet glass or porcelain and forms a brilliant mirror when applied to glass. Some low melting point alloys have Gallium as a component. Because of its low vapor pressure and predictable thermal expansion, Gallium can be used in high-temperature thermometers. Semiconductors are doped with Gallium. The compound Gallium Arsenide can be used to transfer electricity directly into coherent light. Large amounts of Gallium are used in space research to detect solar neutrinos in experiments being conducted in Italy and Russia.

Germanium was discovered in 1886 by Winkler and named for the country Germany. Sources of Germanium are argyrodite, germanite, zinc ores and even coal. The element is commonly recovered from the flue dusts of zinc smelters and the combustion of some coals. Elemental Germanium is a brittle, crystalline metalloid that is relatively stable and will not oxidize in air. Modern techniques allow for the production of extremely pure Germanium. Germanium has favorable conductive properties while the oxide finds use due to its high index of refraction. Germanium is commercially available in its oxide form.

Germanium's primary uses are in the semiconductor industry and transistor manufacture where it is often doped with gallium, arsenic and other elements. It is also used in high-sensitivity infrared devices because Germanium and its oxide are transparent to infrared light. The oxide has a high refractive index and finds use in special glasses for camera and microscope lenses. Germanium is also used in the manufacture of Red-Fluorescing Phosphors, dental alloys and electroplating while Organogermanium chemistry is a becoming field of great commercial interest.

Hafnium was postulated to exist when Mendeleev drafted the first periodic table in 1869. It was discovered many years later by Copenhagen Dirk Coster and Georg von Hevesy in 1923. Elementary hafnium is a shiny, ductile metal that is corrosion resistant. Hafnium is very similar to zirconium. In fact, the two are often difficult to separate. Interestingly, hafnium carbide has the highest melting point for a binary compound at 3890 °C. Additionally, hafnium nitrate has the highest melting point of all metal nitride with a melting point of 3310 °C. This has led to the idea that hafnium might be useful in materials that are subjected to very high temperatures. Hafnium is mainly used in the production of nuclear reactors as a neutron absorber. Hafnium’s ability to absorb neutrons, excellent mechanical properties and corrosion resistant properties make it a good fit. Hafnium is also used in filaments and electrodes and in integrated circuits as a gate insulator.

Indium was discovered by Ferdinand Reich and Hieronymous Theodor Richter in 1863. Richter later went on to isolate indium in 1867. Indium gets is name from the indigo line in its atomic spectrum. Elemental indium is very soft and appears silvery white. Pure indium metal emits a high pitch sound when bent. Indium was first used as coatings for bearings in high performance aircraft engines, during World War II. Eventually new uses were found in fusible alloys, solders, electronics and semiconductors. Indium is also used in the thin-film applications, such as a liquid crystal displays (LCD).

Nickel was extracted by Baron Axel Fredrik Cronstedt in 1751; however, nickel use can be traced back as far 20 B.C. Bronzes from Syria had nickel content up to 100%. Elemental nickel appears as a silver-white metal with a high polish. Nickel is also a very reactive elements, and it is also magnetic. Interestingly, nickel-62 is the most stable nuclide of all existing elements. It surpasses the stability of iron-56. Nickel is mined from two types of ore deposits: laterites and magmatic sulfide. Nickel is most commonly used in industrial and consumer products, such as stainless steel, magnets, special alloys and coinage. Nickel is also used for plating and for the green tint in glass.

Niobium was discovered in 1801 in England from an ore sent there a century earlier from the USA. For 100 years Niobium was also called Columbium until it was made official in 1950, though some still refer to it as Columbium. That name comes from columbite, one of the major sources of Niobium found in North America, Brazil, Nigeria, Zaire, Congo, and in Russia. Elemental Niobium is a lustrous, soft metal and is quite ductile. Niobium metal oxidizes in air at 200^oC. The metal is superconductive and can be used in special magnetic applications. Niobium is commercially available in its metal and pentoxide forms.

Niobium is used in advanced air-frame systems such as those used in the Gemini Space Program and other aerospace products. Special superconductive magnets are made with Niobium Zirconium wire, which retains its conductivity even in strong magnetic fields. Niobium is also popular in alloys and stainless steels and some nonferrous alloys because its presence enhances the strength of the material and is used in pipelines among other things. Some nuclear applications exist because of Niobium's low capture cross-section for thermal neutrons. Niobium pentoxide is also used in some glass and ceramic applications.

Scandium was discovered in 1878 by Nilson. The metal was not extracted until 1937 and it was until 1960 before the first pound of relatively pure sample (99%) was produced. Scandium was originally found in euxenite and gadolinite, but is more commonly collected from the rare mineral thortveitite and Uranium mill tailings. Scandium is believed to be a very common element in stars such as the Sun, but is only the 50^th most abundant element on Earth and is distributed very widely among 800 different earthly species of minerals. Elemental Scandium is a silver-white metal that more resembles the rare earth metals than neighboring Titanium or valence-shell-cousin Aluminum. It is a very light metal and has a melting point much higher than that of Aluminum. Scandium is commercially available in its metal and oxide forms.

Scandium oxide is used for high-intensity lights and Scandium iodide is added to Mercury vapor lamps to produce highly efficient light sources that resemble natural sunlight. The crude oil industry uses Scandium for isotope tracing in refineries. Scandium metal is used in alloys with Aluminum to produce many consumer products such as baseball bats. The metal is also of interest to spacecraft research because of its lightweight and high melting temperature.

Selenium was discovered by Jons Jacob Berzelis in 1817. It occurs in a number of inorganic forms, including selenide, selenate and selenite Some studies have suggested a link between cancer and selenium deficiency. Other studies have indicated a geographical link between regions of selenium deficient soils and peak incidences of HIV/AIDS infection. Selenium has a wide range of applications. It is used in chemical reactions, glass, ceramics, solar cells, photocopying, photography, and in industrial radiography. Selenium is also used in shampoos and in dietary supplements.

Tantalum was discovered in 1802, though it was then thought that Niobium and Tantalum were the same element. In the mid nineteenth century it was proven that Tantalum and Niobium were separate elements. Primary sources of Tantalum are columbite and tantalite ores mined in Australia, Brazil, Africa and Canada, which contain up to sixty percent Tantalum by weight. The separation of tantalum from Niobium is quite difficult and involves several steps. Elemental Tantalum is metallic, heavy, gray and very hard. At temperatures below 150^oC Tantalum is almost completely immune to chemical attack. Only hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulfur trioxide affect the metal at these temperatures. Only two elements have higher melting points than Tantalum, Tungsten and Rhenium. Tantalum is popular in its metal form but is also commercially available in its pentoxide form as well.

Tantalum metal has found many uses in consumer and industrial markets in recent years. The largest applications for Tantalum have been in the manufacture of capacitors. Tantalum's high melting point and superconductive properties have made it popular in many other metal applications as well including filaments, wires, acid-proof chemical equipment and Tantalum Carbide, one of the hardest materials known to man. Several uses exist in the medical field as well as Tantalum metal is nonirritating and immune to all body liquids. Special alloy and single-crystal Tantalum is used in the construction of aircraft parts and strong, ductile steel. The ceramic industry has also found use for Tantalum in dielectrics. Tantalum oxide is also used in the manufacture of special refractive glass for optical applications.

Tin was known to ancient civilizations. It was used as a component of bronze. The word “tin” is thought to be borrowed from a pre-Indo-European language. Its atomic symbol “Sn” comes from the Latin word for tin, “stannum.” Elemental tin is a malleable, ductile, silvery white metal. When tin is bent, a strange cracking sound can be heard. Tin is produced by reducing the ore with coal in a reverberatory furnace. Tin has many applications. It has been used to coat lead or zinc to prevent corrosion. It is also used as plating for food preservation. Tin is also used in windshields, pipe organs, window glass, solder, dental care products and integrated circuits.

Titanium was discovered in 1791 and named for the Titans of Greek mythology. Titanium is the ninth most abundant element in the Earth's crust and is found in the minerals rutile, ilmenite, titanates and many iron ores. The element also exists in the human body. Elemental Titanium is a lustrous white metal with a low density, high strength and excellent corrosion resistance. Titanium metal burns in air and is the only element to burn in Nitrogen. Titanium exists in oxide form as a fine, white powder. The oxide is readily available on commercial chemical markets.

Titanium is important as an alloying agent with aluminum, molybdenum, manganese, iron and other metals. The aircraft, defense and aerospace industries use Titanium in alloys because of its favorable strength, weight and temperature resistance. Titanium is as strong as steel but 45% lighter. Naval applications also exist as result of Titanium's resistance to corrosion, namely its immunity to salt water. Titanium oxide is, when pure, rather clear and has a higher optical dispersion than diamond. The oxide is used in many applications as a pigment because of its indelible white color. Titanium oxide paints are also very reflective of infrared light making them ideal for solar observatories where heat affects viewing conditions. Paint and dye applications account for the widest use of Titanium.

Zirconium was discovered in 1789 by Klaproth in the mineral zircon, which had been known for centuries and is mentioned in biblical writings though it goes by many names. Today, the primary source of Zirconium is zircon ore (ZrSiO₄), which is found in Australia, North America, Brazil and many parts of Asia. Natural Zirconium ores almost always contain Hafnium and separation of the two is somewhat difficult. Elemental Zirconium is a gray-white lustrous metal that is relatively stable in air unless finely divided and/or at high temperature. The metal is resistant to most alkalis, acids, and seawater, among other compounds. Zirconium is commercially available in its oxide form.

Zirconium metal is widely used in nuclear applications because of Zirconium's low absorption cross section for neutrons. The grade used in nuclear applications is essentially free of Hafnium as the impurity introduces undesirable nuclear characteristics. Zirconium is also used in situations that require special corrosion resistance such as surgical appliances and lamp filaments. Zirconium, like Niobium, is superconductive at low temperatures, which may be useful in the field of electricity generation. Zirconium oxide is used in gemological applications when in pure form. The impure oxide is used for shock and heat resistant crucibles and linings. The oxide is also used in the glass and ceramic industries as a refractory metal. This application uses the largest share of the world's Zirconium.

Aqueous solutions

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