Atomic Weight.
—The mean values obtained by Cleve[431] in 1879 were 44·96 and 45·20 by the analytical and synthetic sulphate methods respectively. In the following year Nilson,[432] using purer material, obtained the value 44·13 by the synthetic method. Meyer and others (loc. cit.) have criticised Nilson’s estimation on the ground of his empirical method of obtaining the neutral anhydrous sulphate. Determinations made with material purified from thorium by the iodic acid method gave the values 44·11, 44·11, 44·20; material purified by the double ammonium tartrate method gave the atomic weight 43·90. Meyer has shown that small quantities of thoria in the oxide cannot be detected spectroscopically; the value of the magnetisation coefficient, however, showed the oxide obtained by the last method to be free from thoria, and he considers another determination of the atomic weight to be necessary.
[431] Loc. cit.
[432] Loc. cit.
The value accepted by the International Committee is 44·1.
Detection.
—Scandium gives no absorption spectrum in the visible region. The spark spectrum has been examined by Thalèn (loc. cit.) and Nilson;[433] see also Exner and Haschek, Lockyer and Baxendall,[434] and Crookes (loc. cit.). The arc spectrum has been examined by Fowler,[435] Eder and Valenta,[436] and Exner and Haschek.
[433] Compt. rend. 1880, 91, 56, 118.
[434] Proc. Roy. Soc. 1905, 74, 538.
[435] Phil. Trans. 1908, A, 209, 47.