DiDYMIUM. 25 



Crystalline form monosymmetric: 



a : b : c = 1.61389 : 1 : 1.63433 

 /? = 81''18'. 



Planes: ooP; oP; ooPoo ; +Poo; — Poo; +P. (C.Morton). 



Formiate of didymium 



DiSCHOs. 



This compound was obtained by boiling the oxide of didymium 

 with dilute formic acid. The salt is a light violet powder, composed of 

 microscopic needles. Heated it leaves the oxide in finely divided state. 



0.4982 gram, dried at 100°, gave by evaporation with sulphuric 

 acid 0.5119 gram Di23S04. 



In percent: 



Cal( 



Di^Og 59.64 166 59.93 



C2H2O3 (40.36 ) m 40.07 



100.00 277 100.00 



Spec. Grav: 



0.4616 gram, t" 20", spec. Grav. 3.433 

 0.8500 » » » » » 3.427 



Mean of both determinations: 3.430. 

 Molecular volume: 80.8. 



Acetate of didymium 



I. Di3C2H3 02 + HjO. On evaporating on a water-bath a solution 

 of oxide of didymium in acetic acid fine needles of red colour are 

 deposited. 



0.5467 gram gave by ignition 0.2699 gram DigOä. 



0.7621 gram gave 0.3765 gram DisOs. 



Nova Acta Reg. Soc. Sc. Ups. Ser. III. 4 



