18 SIE WILLIAM CROOKES ON SCANDIUM. 



When cold, the melt is finely ground, mixed with water in the proportion of 1 kilo, 

 to 5 litres, and mechanically agitated for about twelve hours. It is then thrown on 

 a linen filter and well washed. This treatment extracts most of the rare earths, 

 together with a little titanic, iiiobic, and tantalic acids and zirconia, but the bulk of 

 these bodies is left behind. 



The solution is supersaturated with ammonia and well boiled ; this treatment 

 precipitates all the earths, together with iron, titanic acid, zirconia, &c. The 

 precipitate of crude earths is filtered and well washed. 



The precipitated crude earths are converted into oxalates by heating the pasty 

 precipitate in a dish with crystals of oxalic acid added gradually, excess being avoided 

 as much as possible. When cold, the oxalates are filtered off, and the iron, &c., in 

 the filtrate is precipitated with ammonia. As scandium oxalate is slightly soluble in 

 water, the iron precipitate will contain a certain proportion, which must fee kept for 

 subsequent working up. 



The washed oxalates are dried and ignited ; the resulting earths form about 

 17 per cent, of the mineral and contain about 7 per cent, of scandia. 



The crude oxides are converted into sulphates by heating with sulphuric acid, the 

 excess of acid being driven off by heat -not using too high a temperature. The dry 

 sulphates are agitated with plenty of water, and filtered from a little insoluble residue 

 of metallic acids. Ammonia in excess is then added to the filtrate, and the precipitated 

 oxides are washed, once more converted into oxalates in the manner already described, 

 and the oxalates again washed, dried, and ignited. The ignited oxides are boiled in 

 dilute nitric acid, filtered from a little insoluble matter, and evaporated to dryness. 

 These somewhat complicated operations are to insure the removal of sulphuric and 

 metallic acids, the presence of which interferes with subsequent fractionation. 



The earthy nitrates rich in scandium are mixed with an equal bulk of potassium 

 nitrate and fused in large porcelain crucibles with constant stirring until the mass has 

 the appearance of cream fluid when hot, solidifying on cooling to a white enamel-like 

 mass. On boiling this mass in water, a dense white basic nitrate separates and 

 undecomposed nitrates are left in solution. Scandium and ytterbium, forming easily 

 decomposed nitrates, concentrate in the insoluble end the " heads," while the 

 yttrium and cerium earths, whose nitrates are less easily decomposed by heat, are left 

 in the soluble end the "tails." Fractionation on these lines must now be continued 

 until spectrum photographs show the scandium to be pure. It is not difficult to obtain 

 scandia free from all earths present except ytterbia and yttria ; but the final elimination 

 of pure scandia from these earths is a matter demanding much time and patience. 



This easy decomposition of the nitrate by heat makes it possible by a systematic series 

 of fractionations to separate scandium from most of the other associated elements. 

 The worst impurity is ytterbium, the nitrate of which is almost as easily decomposed. 

 Fortunately a strong dominant line of the ytterbium spectrum, wave-length 3694'344, 

 occurs at a vacant part of the scandium spectrum, and near the characteristic group 





