Chem. [mod. L. in form, f. Gr. ἀκτῖν- ray + -IUM, as in sodium, potassium, etc.] A supposed chemical element, a metal discovered in 1881 in association with zinc; so called because of the action of light upon its salts.
1881. Nature, XXIV. 428. The existence of a new metallic element, actinium, in the zinc of commerce. Ibid., No. 620, 470, On the New Metal Actinium, by J. L. Phipson. The sulphide of actinium is described as a pale yellow canary-coloured substance.
