^P. T. C LEVE, 



HISTORY. 



The first indications of the existence of samarium date back to 

 the year 1,878 when Delafontaine') in examining impure did3rmia, extra- 

 ted from samarskite*, observed some new absorption-bands which he ascri- 

 bed to a new metal, having an atomic weight of 106, assuming the oxide 

 to have the formula RO, or 159 if R^Og be the correct formula. He 

 named the new metal decipium. 



Some time later Lecoq de Boisbaudran^) found also in samarskite 

 an oxide the solutions of which were characterised by a peculiar ab- 

 sorption and emission spectrum. He succeeded in separating this oxide 

 from didymia by means of repeated fractional precipitations of the mixed 

 nitrates by dilute ammonia. He called the metallic radical samarium. 

 In 1880 Delafontaine^) published some researches on the compounds 

 of decipium the atomic weight of which he now found to be 114 or 171 

 according. as the formula of the oxide be taken as DpO or Dp^Og. He 

 found the sulphate to be much less soluble than the sulphate of didy- 

 mium. The salts wçre colourless. Shortly after this Marignac*) published 

 a paper on the samarskite earths. By taking advantage of the different 

 solubilities of the sulphates in a saturated solution of potassium sul- 

 phate, he succeeded in separating two oxides which he designated pro- 

 visionally as Yf/. and Yß. The atomic weight of the metallic radical of 

 Yß was 99.6 of 149,4 according to the formula assumed for the oxide. 

 The salts were yellow and gave the absorption-spectrum first observed 

 by Delafontaine and more accurately described bj^ Lecoq de Boisbau- 

 DRAN. The other oxide, Ya, obtained by Marignac was white and gave 

 colourless salts having no absorption-spectrum. The sulphate formed 

 with potassium sulphate a double salt soluble in a saturated solution of 

 potassium 'sulphate, a quantity of this double salt corresponding to 1 

 gram of the oxide dissolving in 100 — ISOcc of the potassium sulphate 

 solution. The corresponding double sulphate of Y/? was much less soluble, 

 while that of the terbia was more soluble. The atomic weight of the 

 metallic radical of Y a was estimated to be as a minimum 104.5 

 (or 156.75). 



1) Comptes rendus LXXXVII, 632. 



2) „ „ LXXXVIJI, 322 and LXXXIX, 212. 



^) Arch, des sc. phys. et nat. [3] III, 250. 



') „ „ . m III, 413. 



