Lanthanum flint

KF = crown flint LaF = lanthanum flint LaSF = heavy lanthanum flint LaK = lanthanum crown LF = light flint LLF = very light flint ... 

Figure 1. Index of refraction versus dispersion and optical classification of glasses shaded area indicates region of glass formation M. Plexiglas is a methyl methacrylate Lucite is an acrylic resin. BaF, barium flint BaK, Barium crown Balf, light barium flint BaSF, heavy barium flint BK, borosilicate crown F, flint FK, fluorcrown K, crown KF, crown flint LaF, lanthanum flint LaSF, heavy lanthanum flint LaK, lanthanum crown LF, light flint LLF, very light flint PK, phosphate crown PSK, heavy phosphate crown SF, heavy flint SK, heavy crown, SSK, very heavy crown, TiF, titanium flint.

Lanthanum is found in rare-earth minerals such as cerite, monazite, allanite, and bastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs in percentages up to 25 percent and 38 percent respectively. Misch metal, used in making lighter flints, contains about 25 percent lanthanum. 

Gr. neos, new, and didymos, twin) In 1841, Mosander, extracted from cerite a new rose-colored oxide, which he believed contained a new element. He named the element didymium, as it was an inseparable twin brother of lanthanum. In 1885 von Welsbach separated didymium into two new elemental components, neodymia and praseodymia, by repeated fractionation of ammonium didymium nitrate. While the free metal is in misch metal, long known and used as a pyrophoric alloy for light flints, the element was not isolated in relatively pure form until 1925. Neodymium is present in misch metal to the extent of about 18%. It is present in the minerals monazite and bastnasite, which are principal sources of rare-earth metals. 

This soft, silver white metal reacts with air and water. The oxide is applied in optical glasses with high refractive indices (special lenses for powerful cameras and telescopes). Used for special effects in optoelectronics and electronics. Lanthanum exhibits catalytic properties. It is a component of flint and battery electrodes. Lanthanum boride (LaB6) is the superior electron-emitter for electron microscopes. Lanthanum is the first of the series of 14 lanthanides, also called the "rare-earth" metals, whose inner N shells are filled with electrons. They do not belong on the "red list" of endangered species they are neither rare nor threatened with depletion. China is particularly rich in lanthanide ores. 

An interesting stage in the development of primer mixes was the use of pyrophoric metal alloys, first patented in 1936 and improved in 1964. These rare earth alloys, as used in cigarette lighter flints, give a shower of sparks when lightly scraped. A typical pyrophoric alloy is misch metal, which has the following approximate composition cerium 50%, lanthanum 40%, other rare earth elements 3%, and iron 7%. 

Cerium is the principal metal in the alloy called misch metal. Misch metal is 50 percent cerium combined with lanthanum, neodymium, and a small amount of iron. Misch metal is used to make the flints for lighters. Cerium is often included in alloys of iron and other metals such as magnesium. A high-temperature alloy of three percent cerium with magnesium is used for jet engines. Some of cerium s compounds—for example, cerium(IV) oxide —are used to polish lenses, mirrors, and televi-... 

Lanthanum has also found modest uses. Its oxide is an additive in high-quality optical glasses to which it imparts a high refractive index (sparkle) and has been suggested for a variety of catalytic uses. Mischmetal , an unseparated mixture of lanthanide metals containing about 25% La, is used in making lighter flints, and more importantly in the production of alloy steels, (p. 1232). 

F means flint glass, e.g. BaF = Barytflint, LaK = Lanthanum crown. 

La20a, in proportions of up to 40%, is used in main optical glass (lanthanum heavy crown and heavy flint). The presence of this oxide endows the glass with a high transparency and improves its structural properties [5]. 

Lanthanum is a metal, soft enough to be exit with a knife, and one of the most reactive of the rare earth metals. It oxidizes rapidly when exposed to air and is attacked by hot water. It is a component of mischmetaU, used for cigarette-lighter flints. The in-termetalhc compound LaNiS is the negative electrode, MH (metal hydride), in the modern Ni-MH alkaline battery. It is an ecofriendly alternative to the nickel-cadmium battery. 

Lanthanum — (Gr. lanthanein, to lie hidden). La at. wt. 138.9055(2) at. no. 57 m.p. 918°C b.p. 3464°C sp. gr. 6.145 (25°C) valence 3. Mosander in 1839 extracted a new earth lanthana, from impure cerium nitrate, and recognized the new element. Lanthanum is found in rare-earth minerals such as cerite, monazite, allanite, and bastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs in percentages up to 25 and 38%, respectively. Misch metal, used in making lighter flints, contains about 25% lanthanum. Lanthanum was isolated in relatively pure form in 1923. Ion-... 

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