DiDYMIUM. 19 



Borate of didymium 



DiBOa. 



Ou adding oxide of didymium to fused borax an amethj^st-colou- 

 red glass is obtained, which heated for some time over a Bunsen burner 

 becomes an enamel. Unter the microscope it appeared as a transparent 

 glass full of minute prisms. The mass was powdered and carefully 

 treated with cold water containing hydrochloric acid. The borax was 

 thus dissolved and a mixture of boracic acid and borate of didymium 

 was left. The boracic acid was dissolved out with boiling water after 

 which the borate was washed with alcohol and dried. The salt was te- 

 sted for sodium, but was free from it. It is easily soluble in hydro- 

 chloric acid. 



0.6648 gram was dissolved in HCl and gave with oxalic acid 

 0.5490 gram DijOg. 



0.5410 gram gave 0.4465 gram DisOg. 



Spec. Grav: 



0.9074 gram, t" 15, sp. Gr. 5.680 

 0.9024 » » » » » 5.721 



Mean of both determinations : 5.700. 

 Molecular volume: 35.3. 



Anhydrometaphosphate of didymium 



Anhydrous sulphate of didymium was added to melting metaphos- 

 phoric acid and heated to redness. The resultant mass, treated with 

 water, left a heavy violet powder, consisting of well formed microscopi- 

 cal, tabular crystals of the same form as the corresponding salt of sa- 

 marium. The salt is insoluble in acids. 



