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Element Lanthanum, La, Lanthanide

About Lanthanum

Lanthanum is a tin-white metal of density 6.155. It is malleable, but not ductile. Its specific and atomic heats (0°-100°) are 0.0449 and 6.23 respectively; its melting-point is 810°. Measurements made with material of doubtful purity indicate that lanthanum is feebly paramagnetic, but this is questionable.

Lanthanum tarnishes rapidly, even in dry air. It burns in air at 440°-460°. The chemical properties of the metal, so far as they are known, are very similar to those of cerium.

Lanthanum Alloys

Little is known of the alloys of lanthanum. Lanthanum alloys with aluminium, and if excess of the latter is taken, and subsequently removed with sodium hydroxide, the compound LaAl4 is obtained. Its density is 3.923 and its heat of formation 97.8 Cals.; it resembles the corresponding cerium compound.

History of Lanthanum

The first period of rare earths research (end of 18th and beginning of 19th centuries) the names of rare earths and their minerals were very confusing. Thus the mineral found in Ytterby, a village on the Swedish island of Resaro and named ytterbite had been renamed in gadolinite after Johan Gadolin's research. A similar rare earth was found by Klaproth and, interpedently, by Jons Jakob Berzelius and Wilhelm Hisinger in mineral cerite. For this reason yttrium and cerium were not distinguished from each other until Berzelius with Gahn demonstrated the difference between them. Both earths had become subject of very thorough research until Mosander in 1826 became convinced that this oxide contained another earth. Ten years later he took up the separations again, and the existence of a new element with properties essentially different from those of cerium became established. The new element had been called lanthanum, from the Greek λανθανω [lanthano] = to lie hidden.

Occurrence of Lanthanum

Lanthanide Lanthanum crustal abundance is 2.9x10-3 mass %., in sea water 2.9x10-6 mg/L. Along with other rare earth elements it is contained in monazite, bastnasite, loparite and in apatite. These minerals are the main source from which Lanthanum may be took out.

Total crustal abundance of lanthanum and lanthanides is estimated to be 1.78x10-2 mass % and is bigger for lanthanides with even numbers. Lanthanides are characteristic elements for Earth crust; their quantities in mantle and meteorites are negligible. Magmatic processes accumulate lanthanides in granitoids and in alkali rocks. Lanthanum forms 9 minerals and cerium 33; other lanthanides make isomorphous in crystal grids of other minerals, mostly those of rare earth elements. In many minerals lanthanides isomorpically substitute calcium, uranium, terbium etc. Lanthanum is poorly mobile in biosphere under most environmental conditions. Data on their migration in are scarce. Some thermal deposits of phosphates, fluorocarbonates and lanthanum fluorides are known; however the most important of them are the complex deposits associated with alkali magmatic rocks and carbonatites as well as deposits of sedimentary phosphorites, alkali rocks residual soil, littoral and alluvial placers of xenotime and monazite.


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