Cerium earths

Cer-erde, /. cerium earth (class name), -erz, n cerium ore, esp. eerite. -feuerzeug, n. m. cerium lighter. 

Fractional precipitation is similar to fractional crystallization technique but takes advantage of basicity differences and solubility differences. Separation of yttrium from yttrium earths by fractional precipitation is an example of differences in basicity. Separation of yttrium earths from cerium earths by double alkali sulfate precipitation in the form of double sulfates is an example of fractional precipitation. 

Xenotime, a rare earth orthophosphate with Th(> , Sit Zr02, etc. The cerium earths vary from 0 to 11 per cent and yttria from 54.1 to 64.7 per cent. Occurs in the diamond sands of Brazil and in Norway. 

Compounds of cerium and its relatives find numerous suggested uses. The pyrophoric metal known as " kunheim is a mixture of the hydrides of the cerium earth metals with magnesium and aluminium. Cerium fluoride and titanofluoride have been used in the preparation of electrodes for the flaming arc light. By impregnating the carbon electrodes with the cerium salts a more intense light is obtained and the arc bums evenly and quietly. Steam declares 1 that 300 tons of ceria are used annually for this purpose. 

The principal supply of thoria is obtained from monnssite sands, which are found in Brazil, India, the Cum inns, Idaho, and in many other localities. Monastic is essentially a phosphate of the cerium earths which contains varying amounts of thorium as an accessory constituent. Originally it is a constituent in pegmatites, granites, and gneisses, in which it occurs... 

From the sulfuric acid solution, thorium may also be obtained by precipitation with sodium fluosilicate, sodium hypo-phosphate,1 or sodium pyrophosphate.2 An ingenious method for removing the phosphorus has been proposed by Basker-ville3 and used on a large scale. It consists in heating in an electric furnace a mixture of monazite, coke, lime, and feldspar. The phosphorus is distilled out and the mass allowed to cool. When extracted with water, acetylene is evolved from the calcium carbide formed during the heating, and the remainder crumbles to a fine powder. This is dissolved in hydrochloric acid, and the cerium earths removed. 

I With samarium-europium samples, other cerium earths are extracted from the amalgam phase only after the bulk of it has decomposed. Fractional decomposition of the amalgam is thus desirable. 

Turning now to the history of the cerium earths we hark back to the close of the eighteenth century. 

The order of the discovery of the cerium earths is summarised in the following scheme —... 

Pure La, Pr and Nd Compounds from Cerium Earths by Ion Exchange... 

The following process is suitable for rapid laboratory-scale separation of cerium earths the cerium is removed from the mixture by precipitation with KMn04 and NagCOa (see below, preparation of pure Ce compounds). The remaining compounds are adsorbed on 250 ml. of a cation exchange resin (Dowex 50 or Wofatit KPS-200 particle size 0.2-0.4 mm.). The resin is then placed in an ion-exchange column (I.D. 4 cm.) which is partly filled with water. A second column of the same I.D. is filled in the same manner with 350 ml. of the resin in the Zn form. 

Yttrium-group earths, containing samarium, separation from mona-zite by magnesium nitrate, 2 56 separation by fractional crystallization of bromates, 2 56, 62 separation from cerium earths by double-sulfate method, 2 44, 46... 

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