DiDYMIUM. 23 



IL a. 0.5714 gram gave by ignition 0.2225 gram DiaOg. 



b. 0.7013 gram gave by the same method as I b. 37.1 cub. cent. 

 NO, t^' 18", pressure 762 m.m. 



In percent: 



I. 

 Di,0, 39.14 



aOa 25.38 



NoOs 11.16—11.85 



H^O '24.66 



872 100.00 



There is some doubt as to the number of mois, of H^O, which 

 the salt contains, as I have found too much Di^Oj and too little N2O5, 

 but it seems to me most probable that the formula given above is 

 the right one. 



'fc>' 



Spec. Grav: 



0.6429 gram, small crystals, t" 13°.2 sp. Gr. 2.424 

 0.6587 » » » » » » » 2.425 



Molecular volume: 359.7. 



Vanadates of didymium. 



1. Orthoimnadate. DiV04. If neutral solutions of metavanadate 

 of ammonium and nitrate of didymium be mixed, a grayish, finely divi- 

 ded precipitate is thrown down, which on washing easily passes through 

 the filter. The precipitate was mixed with an excess of chloride of so- 

 dium and heated to bright redness. After cooling and dissolving out 

 the chloride of sodium an amorphous grayish powder was obtained. 



0.8095 gram was dissolved in hydrochloric acid, sulphurous acid 

 was added to reduce the vanadic acid, and then oxalic acid. The preci- 

 pitated oxalate of didymium left on ignition 0.5166 gram DijOg. The 

 filtrate from the oxalate was evaporated to dryness and heated to destroy 

 the oxalic acid. Nitric acid was then added and the whole evaporated. 

 On igniting the residue 0.2910 gram V2O5 was obtained. It contained 

 0.0084 gram DigO.,. The analysis had thus given 0.5250 gram DiaO^ and 

 0.2826 gram V2O5. 



