[391] Compt. rend. 1907, 145, 759.
The two new elements resemble one another so closely in chemical properties that the account given by Astrid Cleve in 1902[392] of the compounds of the old ytterbium applies in practically every detail to the new elements. The oxides are white, and yield colourless salts, showing in solution no absorption bands in the visible region.
[392] Zeitsch. anorg. Chem. 1902, 32, 129.
The oxides, R₂O₃, though perfectly white, are coloured yellow or brown by the faintest traces of thulium. They are attacked by acids only slowly in the cold, but dissolve readily on warming; lutecia is slightly the less strongly basic. The chlorides crystallise with six molecules of water, and are extremely soluble and deliquescent; when heated in a stream of hydrogen chloride, they form oxychlorides of the type ROCl. The platinocyanides crystallise with 18 molecules of water, and have the characteristic appearance of the analogous compounds of the yttrium elements. The sulphates crystallise at all temperatures as the normal octohydrates, and are moderately easily soluble in water; conductivity measurements show that they are partially hydrolysed in solution. The nitrates crystallise from concentrated aqueous or nitric acid solutions as the tetrahydrates; by evaporation of the aqueous solutions over sulphuric acid, the trihydrates are obtained. These compounds are anomalous among the rare earth nitrates, by reason of their low water content. The neutral carbonates are thrown down by ammonium carbonate as the tetrahydrates; if a stream of carbon dioxide be led into aqueous suspension of the hydroxides, basic carbonates of the formula R(OH)CO₃,H₂O, are obtained. The oxalates are precipitated as the decahydrates; they are readily soluble in excess of alkali oxalate.
Many other salts of the old ytterbium have been prepared.
Atomic Weights.
—The values determined by Urbain (loc. cit.) for the fractions obtained by the nitrate method gave the number 170·1 for the least soluble fraction free from terbium, and 173·4 for the most soluble fraction. Auer von Welsbach (loc. cit.) obtained the values 172·9 and 174·2 for the least soluble and most soluble fractions from the double oxalate crystallisation respectively. More recently[393] he has determined these constants with highly purified material, employing a modified method. The weighed anhydrous sulphates are transformed into the oxalates, which are then ignited to the oxides. He obtained the values Yb = 173·00, Lu = 175·00.
[393] Monats. 1913, 34, 1713.
The values adopted by the International Committee are Yb = 172·0 and Lu = 174·0.