Chem. [f. THOR, the Norse deity + -IUM in other names of metals.
So named by its discoverer Berzelius 1828–9: see Kongl. Vetenskaps-Acad. Handlingar 1829, p. 1. The French having called the earth thorine (see THORINA) named the metal THORINUM, which prevailed also in England for many years.]
A rare metallic element discovered by Berzelius in the mineral thorite, and subsequently found in small quantities in some other rare minerals. Symbol Th. Also attrib.
Now noted as one of the radioactive elements.
1832. Encycl. Brit. (ed. 7), VI. 401/2. Thorina, which constitutes an oxide of thorium, has been hitherto found only in a black mineral…, thoritc. Ibid., 402/1. The only known compound of thorium and oxygen is thorina.
1868. Watts, Dict. Chem., V. 785. Thorinum, or Thorium. Atomic Weight, 115.72; Symbol, Th. Ibid. (1881), VIII. 1967. Thorium … is not isomorphous with any other known element. Ibid. Thorium Oxide [ThO2] … Chloride [ThCl4] … Nitrate … Sulphate [etc.].
1898. Sir W. Crookes, Addr. Brit. Assoc., 24. Rays … emitted by thorium and its compounds. The thorium rays affect photographic plates through screens of paper or aluminium, and are absorbed by metals and other dense bodies.
1903. Daily Chron., 27 Nov., 8/3. He [Sir W. Ramsay] pointed out that the thorium emanations were an ephemeral gas which in two minutes ceased to exist.
1907. Athenæum, 31 Aug., 244/2. Thorium … gives no fewer than seven radio-active products, in the following order: mesothorium, radiothorium, thorium X, thorium emanation, and thorium A, B, and C.
