3863·52 3951·32 4061·27 4156·30 4247·54 4282·67 4303·78 4325·87 4375·11 4385·81 4400·96 4446·51 4451·71 4463·09 4920·84 5923·35 5319·98 5594·58 5620·75 6310·69 6314·69 6385·32 ~Samarium~, Sa = 150·4 The samarium of the earlier chemists (see p. 168) contained a large proportion of the terbium elements, from which a fairly complete separation was first effected by Demarçay in 1900.[291] By the fractional crystallisation of the double magnesium nitrate in presence of bismuth magnesium nitrate, Urbain and Lacombe[292] succeeded in preparing samarium compounds, which were shown by spectroscopic examination[293] to be free from other earths. The element is intermediate in electropositive character and in the solubility relations of its salts between neodymium and the terbium earths; its salts are topaz-yellow in colour, and in concentrated solutions show absorption in the blue and violet regions. The oxide is almost white in colour, with only a faint yellow tinge. A systematic investigation of samarium compounds was carried out by Cleve,[294] but his work was vitiated by the fact that his material was very impure. More recently, the pure salts have been examined by Matignon and his pupils. [291] _Compt. rend._ 1900, ~130~, 1185. [292] _Ibid._ 1904, ~138~, 84 _and_ 1166. [293] Eberhard, _Zeitsch. anorg. Chem._ 1905, ~45~, 374. [294] _Trans. Chem. Soc._ 1883, ~43~, 362; _Bull. Soc. Chim._ 1885, [ii.], ~43~, 53; _Chem. News_, 1886, ~53~, 30, 45, 67, 80, 91, 100. The melting-point of the _metal_ lies between 1300° and 1400°C., so that its preparation by the electrolytic method is a matter of great difficulty. A mixture of the chloride with one-third of its weight of barium chloride is electrolysed by means of a current of 100 ampères, using a cathode of only 2·5 mm. thickness; the metal so obtained is greyish white in colour, and is the hardest of the cerium elements. The _chloride_ separates from aqueous solution as the hexahydrate, SaCl₃,H₂O, in large tabular yellow crystals. The anhydrous chloride is white, but fuses to a chocolate-brown liquid; it forms a large number of additive compounds with ammonia. When heated in an atmosphere of dry hydrogen or ammonia, air and moisture being carefully excluded, it yields the _subchloride_,[295] SaCl₂, as a dark brown crystalline solid, insoluble in alcohol and all organic solvents. Samarous chloride dissolves in water, forming a deep brownish-red solution, which rapidly becomes colourless, with evolution of hydrogen, and precipitation of the oxide and oxychloride. _Samarous iodide_, SaI₂, may be obtained by a similar process, and closely resembles the chloride. [295] Matignon and Cazes, _Compt. rend._ 1906, ~142~, 83.