SIE WILLIAM CEOOKES ON SCANDIUM. 361 



No. 6, mica, contained 0'63 per cent, of rare earths, which, on spectrographic 

 examination, contained an amount of scandium about equal to that in the rare earths 

 in Nos. 3 and 5. 



I have also to thank Dr. A. HIORTH, of Kristiania, for a typical collection of 

 23 specimens of rare minerals from Norway ; the results of examination of most of 

 these specimens have already been given. 



The scandia used in the preparation of some of the salts here described was not 

 absolutely pure. Chemically, no other earth could be detected in it, but the 

 spectrograph revealed traces of yttria and ytterbia. These traces could have been 

 removed by one or more operations, but I thought it advisable to leave them in, for 

 the following reasons : In each operation of purification some loss is unavoidably 

 incurred, and when chemical reactions are insufficient to find the other earths it is not 

 worth diminishing my lessening stock of scandia for the sake of academic purity. 

 The chief reason, however, for leaving these traces in is that they might afford 

 evidence of a difference of behaviour between one earth and another in the presence 

 of some of the acids used. After each quantitative determination the scandia was 

 dissolved in acid and a spectrogram taken to see if yttria or ytterbia were present. 

 The residual earth was then collected from the mother-liquor and a photograph taken 

 of its spectrum. A comparison of the pair of spectra shows at once if any separation 

 has been effected between the earths present. When separation is apparent further 

 experimentation on a larger scale is reserved to a future occasion. 



SCANDIUM IODATE, 

 Sc(I0 3 ) 8 +18H a O. 



Scandium iodate is best prepared by the metathesis of a soluble scandium salt with 

 ammonium iodate. It forms a white crystalline powder almost insoluble in water. 

 After being well washed and dried in the air it contains 18 molecules of water. The 

 water is held loosely ; long drying in a desiccator, or exposure to a temperature of 

 100 and slightly higher, drives some of it off; only by repeated trials with slight 

 alterations of temperature have I obtained certain definite hydrates. There are ' 

 indications of other hydrates, but I have not attempted to prepare them. 



Analysis. 



(1) 15'483 gr. of 18-hydrate scandium iodate, dried in the air at the temperature 

 of about 15, were dissolved in hydrochloric acid and heated until chlorine 

 ceased to be evolved. It was then evaporated to dryness with excess of acid 

 and dissolved in water. Ammonia in excess was added, and the whole boiled. 

 The precipitated scandia was filtered, washed, and ignited. It weighed 

 1-229 gr., = 07959 gr. of scandium. 



VOL. OCX. A. 3 A 



