Atomic Weights of Scandium History

The analogy, though imperfect, between scandium compounds and the compounds of the rare earth elements, points to the tervalency of scandium, and hence, since the combining weight of scandium is 14.7, to the value 44.1 for the atomic weight. The specific heats of the oxide and sulphate may be cited in favour of this view, as the following comparison of molecular heats will show: -

Al₂O₃ – 19.0; Ga₂O₃ – 19.5; In₂O₃ – 22.2; Sc₂O₃ – 20.8; Y₂O₃ – 23.3; Al₂(SO₄)₃ - 63 6; Ga₂(SO₄)₃ – 61.9; In₂(SO₄)₃ – 66.4; Sc₂(SO₄)₃ – 62.4; Y₂(SO₄)₃ – 61.6

If the formula ScO be assumed for the oxide, then the specific heat of scandium works out to the abnormally low value of 3.95 between 0° and 100°, if that of oxygen be taken as 3.0 (which is certainly not too great). The molecular weight of scandium acetylacetonate argues strongly for the tervalency of scandium, as also does the isomorphism of scandium ethyl-sulphate and acetylacetonate with the corresponding indium salts. Of the multiples of the combining weight (14.7, 29.4, 44.1, 58.8, etc.) which might be taken for the atomic weight, only the value 44.1 gives scandium a position in the periodic table, and it then occupies the place of Mendeleeffs " ekaboron."

The value Sc = 44.1 is due to Nilson; the value 45.1 obtained by Cleve is undoubtedly too high. Preliminary experiments by R. J. Meyer and Goldenberg gave the values 44.11, 44.11, 44.20, and 43.90 for the atomic weight of scandium.