Yttrium earths

The bulk of both monazite and bastnaesite is made up of Ce, La, Nd and Pr (in that order) but, whereas monazite typically contains around 5-10% Th02 and 3% yttrium earths, these and the heavy lanthanides are virtually absent in bastnaesite. Although thorium is only weakly radioactive it is contaminated with daughter elements such as Ra which are more active and therefore require careful handling during the processing of monazite. This is a complication not encountered in the processing of bastnaesite. 

Ytter-erde, /. yttria (as class name) yttrium earth, -flussspat, m. yttrocerite, ytterhaltig, a. contammg yttrium, yttriferous, yttric. 

Urbain, G., Twenty-five years of research on the yttrium earths, Chem. Re-... 

Cement, laboratory, 1 189 Cerite, extraction of, 2 44 Cerium, phosphor containing strontium sulfide and, 3 23 separation of, from rare earth mixtures, 2 43, 47, 48 test for, 2 50 Cerium amalgam, 1 15 Cerium-group earths, separation of, from yttrium earths by doublesulfate method, 2 44, 46 Cerium (III) magnesium nitrate, 2Ce(N03)s-3Mg(N03)2-24H,0, separation of praseodymium from lanthanum by, 2 57 Cerium(III) nitrate, 2 51 Cerium (IV) nitrate, basic, 2 49 Cesium, cesium azide for preparation of, 1 79... 

Classical methods of separation [7] are (1) fractional crystallization, (2) precipitation and (3) thermal reactions. Fractional crystallization is an effective method for lanthanides at the lower end of the series, which differ in cation radius to a large extent. The separation of lanthanum as a double nitrate, La(N03)3-2NH4N03-4H20, from praseodymium and other trivalent lanthanide with prior removal of cerium as Ce4+ is quite a rapid process and is of commercial significance. Other examples are separation of yttrium earths as bromates, RE(Br03>9H20 and use of simple nitrates, sulfates and double sulfate and alkali metal rare earth ethylenediamine tetraacetate complex salts in fractional crystallization separation. 

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. 

The lanthanide contraction is probably the reason why the natural processes lead to fractionation and give rise to cerium group elements containing mainly the larger rare earth elements of lower atomic numbers, and to yttrium earth minerals containing mainly smaller rare earth elements with higher atomic numbers. Yttrium, although not a rare earth element, its atomic number 39 is low and its radius is similar to that of Ho. Thus yttrium appears with heavy rare earth elements. 

From this table it is evident that all monazite contains much more ceria than thoria and since the mantle is mainly thoria a very large part of the ceria is not needed for mantle manufacture. The residue which remains after removal of the thoria contains about 45 per cent Ce02,25 per cent La203, and 15 per cent didymia, the remainder being yttrium earths, samaria, etc. The residue represents 60-65 per cent of the original monazite. Since the total world s consumption of monazite has been estimated as being about 88,000 tons up to 1918, it is evident that the supply of cerium material has been very large. Some firms have stored enormous quantities of these rare earth salts, and others have thrown them away. The residues are transformed to the chlorides, which are carefully dehydrated to prevent the formation of basic salts. The purity of the chlorides is not important, but the phosphorus and sulfur content must be low, and iron and aluminium should not be present in more than small amounts. A mixture of the... 

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

If the original material contained any considerable quantity of xenotime, the yttrium earths (which will be present) will not be precipitated completely by sodium sulfate. In such a case, solid oxahc acid may be substituted for the sodium sulfate or. added to the filtrate from the sulfate precipitation. Otherwise, the filtrate may be discarded. Solid oxalic acid is preferable to the saturated solution in that it does not further dilute the solution and does not form any troublesome gummy precipitates, which must be heated or allowed to stand for some time before effective filtration may be obtained. Ordinarily, the use of oxalic acid is not justified because of the greater expense involved. 

Separation of Cerium and Yttrium Earths by the Double Sulfate Method)... 

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