ERBIUM SALTS. 



63 



Erbium Chloride in Glycerol. 



Several photographs (Plate 29, A and B) were made of the absorption 

 spectra of erbium chloride dissolved in glycerol. The absorption is very- 

 similar to that of an aqueous solution; the bands, however, in general being 

 shifted towards the red. The bands shown by a solution 30 mm. in depth 

 are located as follows: X 3250; X 3370; A 3510. These three bands are quite 

 strong, being some 30 or 40 Angstrom units wide; X 3600 is weak and narrow; 

 X 3650 is quite strong; X 3785 is quite strong; X 3885 is considerably weaker 

 than the five other ultra-violet bands described above; X 4165; X 4490 and 

 X 4520 are of about equal intensity and quite strong (in the region near these 

 bands there are numerous weak bands and these would come out better if 

 a greater depth of cell could have been used, but on account of the slight 

 solubility of erbium chloride in glycerol the use of a greater cell-depth was 

 not practicable); X 4910 weak; X 5190; X 5210; X 5225 rather strong; X 5240 

 weak; X 5260 weak; X 5380; X 5420; X 5440; X 6450; and X 6530. The meas- 

 urements were from a spark-line at X 3995 and hence are more accurate 

 in this region. On the whole, most of the erbium chloride bands are of 

 greater wave-length for the glycerol solution than for the aqueous solution. 



The relative intensities of the water and glycerol bands differ consider- 

 ably, but the wave-lengths do not appear to be very greatly changed. The 

 photographic films appear to have contracted differently on drying, so that 

 no very accurate comparisons of the wave-lengths of the water and glycerol 

 bands could be made. 



Rise in temperature from 15 to 200 produces no noticeable change 

 in wave-length. At the higher temperature the bands are very much less 

 distinct and apparently considerably weaker. For instance, the group of 

 bands at 15 at X 5200 practically becomes a single hazy band at 200. 



Erbium Chloride in Water, Effect of Temperature. 



A spectrogram (Plate 30, B) was made to show the effect of rise in 

 temperature on the absorption spectrum of an aqueous solution of erbium 

 chloride. For this purpose a 0.94 normal solution was used and the depth 

 of layer was 48 mm. The solution probably contained a considerable 

 number of impurities, so that the amount of erbium was in fact quite small. 

 The absorption spectrum was found to change but little with rise in tem- 

 perature, thus indicating a dilute solution. Exposures were made for 30 

 seconds to the Nernst glower and 4 minutes to the spark. The current 

 through the glower was 0.8 ampere and the slit-width 0.20 mm. Starting 

 with the spectrum nearest the comparison scale, the temperatures were 

 7, 17, 29, 46, 60, 70, and 80. 



At 70 the ultra-violet is absorbed to X 3950. As the temperature is 

 raised the ultra-violet absorption increases, and at 80 it reaches X 3150. 



