The chloride, TmCl₃,7H₂O, separates at ordinary temperatures from the concentrated solution of the oxide in hydrochloric acid as greenish crystals, very soluble in alcohol and water. The bromate, Tm(BrO₃)₃,9H₂O, forms pale bluish-green hexagonal prisms, isomorphous with the analogous salts of the group. The sulphate and nitrate separate as the octohydrates. The precipitated oxalate has the formula Tm₂(C₂O₄)₃,6H₂O, and is soluble in excess of alkali oxalate. The acetylacetone derivative was prepared by dissolving the precipitated and well-washed hydroxide in alcoholic acetylacetone; it recrystallises from absolute (?) alcohol as the dihydrate, Tm₂(C₅H₇O₂)₆,2H₂O. The phenoxyacetate, Tm₂(C₆H₅·O·CH₂·COO)₆,6H₂O, was obtained in a similar manner by addition of the hydroxide to a solution of phenoxyacetic acid in dilute alcohol.
Atomic Weight.
—Cleve gave the value 170·7 for this constant, but his material was very impure. In a footnote to a paper published in 1907, Urbain[388] pointed out that the value could not be above 168·5. Analyses of the salts prepared by James agree fairly well with the theoretical values calculated on this basis, but a systematic determination with pure material has not yet been made. The International Committee (1912) have adopted the value 168·5.
[388] Compt. rend. 1907, 145, 760.
Detection.
—The element can be detected in solution by its absorption spectrum, the most intense bands being in the neighbourhood of λ = 685, and λ = 464. For provisional arc spectra see Exner and Haschek, and for spark spectra Auer von Welsbach (loc. cit.) and Eder and Valenta.[389]
[389] Sitzungsber. kaiserl. Akad. Wiss. Wien, 1910, 119, IIa, 103.
Ytterbium (Neoytterbium, Aldebaranium), Yb = 172·0.
Lutecium (Cassiopeium), Lu = 174·0.
The first indication of the complexity of Marignac’s Ytterbium was furnished on spectroscopic grounds by Auer von Welsbach in 1905;[390] he showed that a separation could be effected by the fractional crystallisation of the ammonium double oxalates from concentrated ammonium oxalate. Three years later[390] he published a full account of his method, gave atomic weight determinations, and mapped the spectra of the two new elements. In 1907, Urbain[391] independently effected a separation by the fractional crystallisation of the nitrates from nitric acid, and proposed the names Lutecium (from the old name for Paris) and Neoytterbium for the elements.
[390] See Monats. 1908, 29, 204.