DiDYMIUM. 5 



TLe above six experiments give as a mean 8.12 parts oxygen 

 for 100 parts DigOa, approximating to the quantity required by the 

 formuhi DiiOç,, viz. 7.23 parts oxygen for 100 parts DigOj. The formula 

 Dis 0.1 requires 9.64. Some other experiments'), in which the peroxide was 

 precipitated with ammonia, gave as a mean 7.28 parts oxygen for 100 

 parts Di^, 0., . 



Chloride of didymium 



DiCls + eH^O. 

 Large, violet, and easily soluble crystals, deliquescent in moist air. 



0.8049 gram gave 0.641.5 gram DigSSOj. 

 0.5980 » » 0.70.S7 » AgCl. 



In percent: 



Di 39.57 142.0 39.83 



CI 29.11 106.5 29.87 



H2O (31.32) 108.0 30.30 



356.0 100.00 

 Spec. Grav: 



1.3308 gram, large crushed crystals, t" 15*^.8 sp. Gr. 2.287 

 1.4372 » » » » » » 2.286 



Molecular volume: 155.9. 



Crystalline form asymmetric. The crystals are elogated pa- 

 rallel to oP: 



a : b : c = 1,37326 : 1 : 1.87177 



a = 89" 46' 4" . ß = 119" 44' 55" . y = 84° 57' 4". 



Observed planes: 00 P^; 00 ^P; 00 P c»; è,P; oP, . (C. Morton). 



Oxichloride of didymium 



Di O Cl. 



If the oxide of didymium be heated in a current of chlorine, it 

 ignites and gives a grayish powder consisting of the above oxichloride 

 which is very hygroscopic. 



») Bullet. Soc. Chiin. XLIII, p. .56. 



