[ 15 } 



II. On Scandium. 



By Sir WILLIAM CROOKKS, D.Sc., F.R.S. 



Received March 4, Read April 30, 1908.* 



[PLATE 1.] 



SOANDIA is one of the rarest and least known of the recognised rare earths. It was 

 discovered in 1879 by NlLSON, who separated it, with ytterbia, from erbia extracted 

 from euxenite and gadolinite. NILSON made an incomplete chemical examination 

 of some of its compounds, but owing to the inadequate amount of material at his 

 disposal he did not at first entirely separate it from ytterbia. Later in the same 

 year CLEVE extracted scandia from gadolinite, yttrotitanite, and keilhauite, and 

 described the scandium sulphate, double sulphates, nitrate, oxalate, double oxalates, 

 selenate, acetate, formate, oxide, and hydrate, and gave some of the chief reactions of 

 the new body. 



CLEVE, working on gadolinite, found that it contained only from 0'002 to O'OOB per 

 cent. of scandium, while keilhauite yielded only about O'OOo per cent. He 

 gave results from which he deduced an atomic weight of about 45. CLEVE noticed 

 that scandium almost exactly corresponded to the description given by MENDELEEFF 

 of his hypothetical element " ekaboron," of atomic weight 44. More recently, in 

 1880, NILSOX, working on somewhat larger quantities of scandia, described and 

 analysed the nitrate, sulphate, selenate, oxalate, and the potassium double sulphate. 

 He found the atomic weight to be 44 '03, the mean of four separate and closely 

 concordant determinations. Taking NILSON'S data, and re-calculating from them the 

 atomic weight of scandium, using the most recent figures for oxygen and sulphur, 1 

 find his atomic weight to be almost exactly 44'1 a figure I have used in the 



cj ./ O 



following paper. 



In the course of my 20 years' work on the fractionation of the rare earths I have 

 repeatedly tested my products by examining their photographed spectra, using the 

 dominant lines of the various elements as tests for their presence. Scandium has an 

 extremely characteristic group of lines in its spectrum, situated between wave-length 

 3535-864 and wave-length 365T983, the strongest being at 3613'984, midway 

 between two strong iron lines. By using a part of the spectrum in which this 

 line occupies the centre of the photograph, it is easy to recognise scandium. 

 Detecting the dominant line, the presence of scandium can be verified by reference to 

 the other lines of the group. (See the plate at the end of this paper.) 



* The descriptions and analyses of the Fluoride, Succinate, Benzoate, the Toluates, Phenyl-acetate, 

 Pyromellitate, and Camphorate were received June 25, 1908. 



VOL. CCIX. A 442. 4.11.08 



