Yttrium-group earths, containing

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... 

Yellow liquors containing principally yttrium-group earths with samarium will be obtained from the most soluble fractions and wUl fail to crystallize. These may be removed from the series to be combined later with other materials of similar composition obtained in the same manner. When these fractions are of sufficient volume they should be used for the preparation of bromates (synthesis 17). 

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... 

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. 

Source Monazite, bastnasite, and related fluocarbo-nate minerals as well as minerals of the yttrium group. These ores contain varying percentages of rare-earth oxides, which are often loosely called rare earths. Rare earth elements also occur as fission products of uranium and plutonium. 

Monazite, the orthophosphate of the cerium group rare earths, is, without doubt, the most important rare earth mineral. It contains cerium-group oxides (49 to 74 per cent), yttrium-group oxides (1 to 4 per cent), thoria (1 to 20 per cent), and variable quantities of silica, iron (III) oxide, alumina, etc. Typical commercial samples of... 

Xenotime, the orthophosphate of the yttrium-group rare earths, contains yttrium-group oxides (54 to 67 per cent) and cerium-group oxides (1 to 11 per cent), together with silica, thoria, zirconia, etc. It is neither as abundant nor as widespread in its occurrence as monazite, but has been reported from Norway, Sweden, Brazil, Colorado, North Carolina, and a few other localities. 

Substitution of the R element also affects the character of interaction in the systems. The number of compounds formed is 10 in La-Ni-P, 15 in Ce-Ni-P, 13 in Nd-Ni-P, 11 in Sm-Ni-P, 12 in Eu-Ni-P, and 9 in Tb-Ni-P. The number of compounds containing light rare earths is greater than in systems containing an R of the yttrium group. 

The 3rd group of the Periodic Table (the 1st column within the block of the transition elements) contains the metals scandium, yttrium, lanthanum, and actinium. Lanthanum (atomic number 57) may be considered the earliest member of the family of metals, called lanthanides (general symbol Ln), forming, inside the principal transition series, an inner transition series (up to atomic number 71). Scandium and yttrium together with the lanthanides are also called rare earth metals (general symbol R). 

The final answer came from the atomic pile. J. A. Marinsky, L. E. Glendenin, and C. D. Coryell at the Clinton Laboratories at Oak Ridge (20) obtained a mixture of fission products of uranium which contained isotopes of yttrium and the entire group of rare earths from lanthanum through europium. Using a method of ion-exchange on Amberlite resin worked out by E. R. Tompkins, J. X. Khym, and W. E. Cohn (21) they were able to obtain a mixture of praseodymium, neodymium, and element 61, and to separate the latter by fractional elution from the Amberlite column with 5 per cent ammonium citrate at pH 2.75. Neutron irradiation of neodymium also produced 61. 

We have not discussed in detail the transition metals of Groups Ilia, IVa, Va, or Vila. The first of these four, the scandium group, contains the rare and invariably tripositive metals, scandium (Z = 21), yttrium (Z = 39), and lanthanum (Z = 57) these elements are best considered with the rare earths and will not be taken up in this text. 

Scandium, yttrium, and lanthanum, in group Ilia of the periodic table, usually occur in nature with the fourteen rare-earth elements, cerium (atomic number 58) to lutetium (atomic number 71). All of these elements except promethium (which is n ade artificially) occur in nature in very small quantities, the principal source being the mineial monazite, a mixture of rare-earth phosphates containing also some thoriurn phosphate. 

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