DiDYMIUM. 27 



Crystalline form of II asymmetric: 



a : b : c = 1.91305 : 1 : 2.21946 



a = 90" 19' 40"; ß = 104" 33' 50"; y = 90° 19' 20". 



Planes: ooPoo; oP; P, oo; P'; 'P; P,; ,P. (C.Morton). 



Propionate of didymium 



Di3C3H5 02 + 3H2 0. 



Dilute propionic acid dissolves the oxide of didymium, and the 

 solution deposits on evaporation at the ordinary temperature violet prisms, 

 which are tolerably soluble in water. They lose their water of crystal- 

 lisation slowly in the air. 



0.3300 gram of the crystallised salt lost at 100" 0.0430 gram and 

 left on ignition 0.1322 gram DigOg. 



0.7070 gram lost at 100" 0.0925 gram and left 0.2844 gram DigOg. 



0.3327 gram gave on combustion 0.1554 gram H^O and 0.3196 

 gram CO2. 



In percent: 



^ Ca^^ 



Di^O^ 40.06 40.23 — 166 40.00 



C — — 26.20 108 26.02 



H — . — 5.19 21 5.06 



O — — — 120 — 



415 

 Ha O 13.03 13.03 — 54 13.01 



Spec; Grav. of the crystallised salt: 



0.6218 gram, t" 12''.5, sp. Gr. 1.741 

 0.6465 » » 13" » » 1.742 



Molecular volume: 238.4. 



Spec. Grav. of the anhydrous salt. 



0.5351 gram, t" 12".5, sp. Gr. 1.861. 



Molecular volume: 194. 



