Samarium, atomic weight of, 182 detection of, 183 history of, ~168~ metallic, ~115~, 181 salts of, ~182~ separation of, ~171~ Samarskite, 24, 38, ~60~, 91 Scandium, atomic weight of, ~217~ chemical relations of, ~214~ compounds of, ~215~ detection of, ~218~ history of, 194, ~213~ occurrence of, ~3~ separation of, ~186~ Schorlomite, 24, 55 Scovillite, 23, 88 Selenates of rare earth group, ~128~ Selenites of rare earth group, ~128~ Semelene, 54 Senaite, 24, 59 Silicofluorides of rare earth group, ~121~ Sipylite, 24, 39, ~63~ Spark spectra, ~150~ Sphene, 26, ~52~, 90, 107 Steenstrupine, 25, 51 Strüverite, 25, 71 Sulphates of rare earth group, ~124~ Sulphides of rare earth group, ~119~ Sulphites of rare earth group, ~127~ Synchisite, ~81~ Tachyaphaltite, 25, 49 Tautolite, 42 Tengerite, 25, 81 Terbium, atomic weight of, ~192~ detection of, 193 group, chemical relations of, ~185~ history of, ~184~ separation of, ~186~ history of, ~184~, 191 salts of, 192 Thalénite, 25, ~43~, 102 Thiosulphates of rare earth group, ~127~ Thorianite, 25, ~73~, 107, 251 Thorite, 25, ~45~, 108, 251 Thorium, atomic weight of, ~262~ chemical relations of, ~251~ compounds of, ~254~ detection of, ~263~ estimation of, ~285~ extraction of, 251, ~275~, 283 group relations of, ~220~ metallic, ~253~ radiochemistry of, ~252~ separation of, ~277~ sulphate purification of, ~279~ Thorogummite, 26, 49 Thortveitite, 26, ~44~ Thulium, history of, ~194~, 203 individuality of, ~204~ salts of, ~204~ separation of, 196 Titanates, ~234~ Titaniferous ironstone, ~57~ Titanite, 26, ~52~, 90 Titanium, atomic weight of, ~236~ compounds for fixation of nitrogen, ~337~ compounds of, in dyeing, ~333~ compounds of divalent, ~225~ compounds of trivalent, ~226~ compounds of tetravalent, ~230~ cyanonitride, ~224~ detection of, ~236~ electrodes, ~331~ estimation of, ~338~ group relations of, ~219~ metallic, ~223~ occurrence and extraction of, ~222~ olivine, 26, 55 steels, ~329~ uses of, in metallurgy, ~327~, ~330~ Tritomite, 26, 51 Tscheffkinite, 26, 55 Tungsten, 1, 31 Turnerite, 83 Tyrite, 63 Tysonite, 26, 89 Uhligite, 27, 59 Uraninite, 29, ~52~ Uranosphærite, 73 Urano-tantalite, 60 Vasite, 42 Vietenghfiote, 27, 64 Viscose process, ~304~ Warwickite, 27, 59 Weibyite, 27, 81 Wiikite, 27, ~70~ Wöhlerite, 28, 70 Wolframite, 2, ~214~ Xenotime, 28, 45, ~86~, 90, 207 Ytterbia, 1, 206 Ytterbite, 1, 33 Ytterbium, atomic weight of, 206 detection of, 207 history of, ~194~, 205 salts of, ~206~ separation of, 196, ~205~ Yttria, 1, 35, ~111~, 209 Yttrialite, 28, ~34~, 45