DIDYMIUM. 51 



recovered and determined as sulphide. For S = 16.037 and 

 = 8, these experiments gave Cu = 31.6577 and 31.66. 

 The vahie taken is the mean of the two series. All weigh- 

 ings were reduced to vacuum. [Zeitschr. fiir Berg Hutten- 

 unci Sal.-Wesen im Freus. St., 21, 1873, 260.) 



DIDYMIUM. 



W. F. Hillebrand found the specific heat of this metal 

 0.04563, which corresponds to an atomic heat of 6.60 for 

 an atomic weight of 144.78. [Foggend. AnnaL, 158, 1876, 78.) 



C. Marignac: U8.8 (0 = 16); 930 (O = 100). 



Determined by decomposing disulphate with barium chlo- 

 ride. Assuming the lower oxide as a prot-oxide, he calcu- 

 lated the atomic weight at 620. As Marignac was not 

 confident of the purity of his salt, and subsequently became 

 certain that the method was untrustworthy, details are 

 unnecessary. [Liebig^s AnnaL, 71, 1849, 313.) 



C. Marignac : 143.81 (0 = 16) ; 898.8 (0 = 100). 



Five experiments were made on the sulphate by decom- 

 position with ammonium oxalate. The didymium oxalate 

 was heated to redness, and the resulting oxide weighed. 

 On the assumption that the oxide was protoxide, these 

 determinations gave a mean of 598.2 for Di, with an ex- 

 treme difference of 2.5. Three experiments were made on 

 the chloride, the insoluble oxychloride, which is unavoida- 

 ble in drying the salt, being separated. The chlorine was 

 determined with silver, and the Di as in the previous experi- 

 ments. These determinations gave Di at 600.2, with an 

 extreme diflerence of 5.2 for CI = 443.2 and S = 200. The 

 salts were prepared from cerite. The cerium was extracted 

 by treatment at first with dilute and afterwards with con- 

 centrated nitric acid. The sulphates of Di and La were 

 separated by partial precipitation with oxalic acid and by 

 partial recrystallization. {ArniaJ. de Chimie et de Fhys., (3,) 

 38, 1853, 148.) 



R. Hermann : U^.U (0 = 16) ; 890.25 (O = 100). 



In one experiment sulphate which had been heated to a 

 low red heat, was dissolved, decomposed with ammonium 



