OXIDE OF SELENIUM. 515 



colored flakes. When the solution was strong, the precipitation was 

 immediate ; if dilute, it was more tardy, and the color varied from 

 bright red to dark gray. The selenium was washed with 5 or 6 

 parts of cold distilled water, till muriate of baryta gave no precipitate, 

 and lastly, it was dried in the shade. 



The selenium still contained in the liquor is obtained by concen- 

 tration, by evaporating to two thirds the bulk, and the addition of 

 more sulphite of ammonia, and finally by immersing bars of zinc, 

 taking care that these do not remain in too long, and thus mix their 

 own substance with the selenium.* 



4. PROPERTIES. 



(a.) Color various ; if rapidly cooled, dark brown, or gray, or of 

 a leaden color, and metallic lustre, it often resembles polished he- 

 matite ; when in powder of a deep red, adheres by pounding, and its 

 surface gray and smooth. 



(b.) It is not hard, but it is brittle; fracture conchoidal, of the 

 color of lead, and perfectly metallic; lustre vitreous. 



(c.) Sp. gr. between 4.31, and 4.32. 



(d.) Jit 212 soft and ductile, like Spanish wax, and may be 

 kneaded between the fingers, or drawn into fine translucent threads, 

 wiiich have a metallic aspect ; " red by transmitted, but gray by 

 reflected light." Becomes quite fluid, at a temperature considera- 

 bly above that of boiling water, and near that of boiling mercury, or 

 about 650, it boils, and may be distilled in a retort, condensing like 

 mercury, in metallic drops, or if a retort with a large neck is used, 

 or sufficient space to mix it with cold air, in a light sublimate, of a 

 fine cinnabar color. Its vapor is of a color between that of chlorine, 

 and that of the vapor of sulphur. If cooled slowly, it assumes a 

 granulated fracture, like that of cobalt. 



(e.) At the boiling point its vapor is inodorous ; but under the 

 blowpipe a piece not over j\ of a gr. will Jill a large room with the 

 smell of horse radish : it tinges the blowpipe flame of a fine azure 

 blue. 



(/.) Insoluble in water ; not altered by the air. 



(g.) A non-conductor of heat and electricity, and does not become 

 electric by friction. 



OXIDE OF SELENIUM. 



(a.) The peculiar odor is developed when the exterior flame of 

 the blowpipe is applied, and is caused by the combination of selenium 



* The sulphureous deposit examined by Mr. Lewenau was from ^ sulphuric acid 

 manufactory, in Hungary : it was much richer than that of Sweden, and afforded 

 591.82 grs. to the pound of the crude substance, of which 484.16 was from the first 

 precipitate. Ann. Phil. N. S. Vol. VIII, p. 106. In one instance, the material of 

 Sweden gave Berzelius only 0.0015 of its weight. 



