CHEMISTRY. 631 



which of the numbers represents, or more nearly approaches, the true 

 atomic weight, and to ascertain whether pure didymium is a homoge- 

 neous body, or whether it can be split up into heterogeneous constit- 

 uents, as has been proved to be the case with several metals of the 

 rare earths. Brauner found by his new experiments Di = 145.42. This 

 number differs much from that previously obtained by Brauner, who 

 believes the discrepancy due to the elimination of an element of a 

 higher atomic weight and of a less basic nature than didymium. This 

 proved to be samarium, q. v. (J. Ghem. Soc, 1883, 278.) 



P. T. Cleve has also examined this question, and having eliminated 

 foreign bodies by fractional precipitation he obtained the value Di = 

 142.33, when O = 16. He had previously obtained (in 1874) Di = 147.2, 

 but he attributes the discrepancy to the presence of the then unknown 

 element samarium. (Bull. soc. chem., xxxix, 289.) 



/Samarium. — Brauner, in the course of his researches into the atomic 

 weight of didymium, investigated the atomic weight of samarium, and 

 assigns to it the value 150.7. (J. Ghem. Soc, 1883, 278.) 



P. T. Cleve has also determined the atomic weight of samarium by 

 converting the pure oxide Sm 2 3 into the sulphate, and obtained from 

 six closely agreeing experiments the value 150.021, or, in round numbers, 

 150. Cleve thinks samarium entitled to fill the eighth line, eighth 

 group of MendelejefPs Periodic System. (J. Ghem. Soc, 1883, 362.) 



Lanthanum. — In 1874 P. T. Cleve found the atomic weight of La=139., 

 figures which agreed well with determinations by Marignac and Brau- 

 ner. More recent investigations by Brauner led to the value 138.28, and 

 his researches seemed to denote the existence of a foreign oxide accom- 

 panying the lanthanum. Cleve himself was at one time inclined to ad- 

 mit the existence of such a substance by the observation of a blue ray 

 (X = 4333.5) in the spectrum of the fractions intermediate between lan- 

 thanum and didymium; but this ray proved to belong to lanthanum. 

 To decide the question of the existence of this hypothetical body between 

 La and Dd, Cleve submitted mixtures to several series of partial precipi- 

 tations by dilute ammonia. His results give for La 138.019 (O = 15.9633). 

 They also show that La is not split up, but is a homogeneous body. 

 (Bull, soc chem., xxxix, 151.) 



Yttrium has again been examined by P. T. Cleve, who effected a more 

 complete separation from terbium by precipitating the acid solution of 

 the nitrate by means of oxalic acid. In the successive fractions thus 

 obtained Cleve determined the atomic weight, which he places at 89.02 

 for Y IU , when 0=16. Determinations by the same author in 1872 gave 

 him 89.485. (Comptcs rendus, December 11, 1882.) 



" Thorium has been re-examined by L. F. Nilson, who determined its 

 specific heat, and thence estimates the atomic weight at 232.4 for Th lv . 

 (Comptes rendus, xcvi, p. 346.) 



