ERBIUM OXIDE. 



117 



yttrium oxide, of unknown purity, all of which were a beautiful yellow 

 color, as compared with the sample given in fig. 83, which was a yellowish- 

 white. These samples were obtained by fractional precipitation from the 

 sulphate of yttrium by means of oxalic acid. The precipitation, however, 

 was not carried out to the extent of obtaining yttrium, erbium, and ytter- 

 bium oxides separately. In these curves the prominent bands of fig. 83, 

 with maxima at 2 and 2.75 fi, are suppressed, and the small bands of the 

 latter at 3 and 6.8 li are the most prominent. These three samples were 

 heated so that the surface appeared a dull red, the sample for curve b 

 being the hottest. The emission bands occur in two groups, at 3 and 

 6.8 li, respectively, just as was found in the oxides of zirconium and mag- 

 nesium. There are sharp maxima at 2.8, 3.15, and 6.75 ju, and smaller 

 bands at 2, 3.9, and 5.2 li, respectively. 



3 4 5 6 



Fig. 85. Erbium oxide. 



Erbium Oxide (Er 2 3 ). 

 (Curves a and b, fig. 85.) 



Curve a shows the emission of a layer of the oxide formed by decom- 

 posing a solution of the nitrate on a strip of platinum, heated electrically. 

 Curve b gives the distribution of energy of a layer of the oxide on a heater- 



