46 THE ABSORPTION SPECTRA OF SOLUTIONS. 



bombardment by /3 rays, if they do not show any effect by a rays. Recent 

 studies of phosphorescent screens subjected to a-ray bombardment has led to 

 the belief that these substances are composed of aggregates. 



THE ABSORPTION SPECTRUM OF GADOLINIUM. 



Very little has been done on the absorption spectrum of gadolinium. A 

 dilute nitrate solution in a 10 mm. layer showed several weak bands at X 3500 

 to X 3390, with a maximum at X 3470. A weak band appeared at X 3300 to 

 X 2890 and continuous absorption commenced at about X 2200. According to 

 Soret there is a band from X 2800 to X 2450. 



Gadolinium Chloride in Water. 



B, plate 28, shows the absorption of a solution of gadolinium chloride, 

 1.407 normal; the depths of cell starting from the lowest strip being 2, 10, 15, 

 22, 22, and 100 mm. The spectrogram shows that there is quite a strong, 

 general absorption in the ultra-violet, amounting to several hundred Ang- 

 strom units in the case of the 2 mm. length of layer, transmission beginning 

 at about X 2700. For the 100 mm. length of layer this absorption extends 

 to about X 3700, the edge of the transmission being very broad. 



The plate shows, besides this general absorption, two very sharp bands at 

 X 2925 and X 2980. These appear dearly for the 10 mm. layer. For the 100 

 mm. layer a weak band, about 25 Angstrom units in width, appears at X 3910. 

 A very weak band appears at X 3970. This band is so weak that it can hardly 

 be seen in the original film. 



Gadolinium Chloride in Ethyl Alcohol. 



Plate 28, A, gives the absorption of a 0.8 normal solution of gadolinium 

 chloride in ethyl alcohol; the depths of cell, starting from the lowest strip, 

 being 2, 4, 9, 18, 27, and 27 mm. 



One of the most pronounced characteristics of the absorption of this 

 alcoholic solution is the enormous absorption in the ultra-violet, compared 

 Avith the aqueous solution. The edge of this absorption is very diffuse. It 

 extends to about X 3000 for the 2 mm. solution, and to about X 4400 for the 

 27 mm. solution. 



The only characteristic part of the absorption spectrum is a very diffuse 

 band at X 4360. This band is gradually included in the region of general 

 absorption, as the depth of cell is increased. 



It will be noticed that the absorption spectra of the alcohol and aqueous 

 solutions are very different indeed. 



THE ABSORPTION SPECTRUM OF DYSPROSIUM. 



Very little work has been published on the absorption spectrum of dyspro- 

 sium. Lecoq de Boisbaudran 1 has described the following bands arranged 

 according to the intensity of the bands: Dya, X = 4515; Dy(3, X = 4750; Dyy, 

 X=7565; Dy8, X=4275. 



Urbain 2 has observed only X 4740 and a weak band at X 4530 to X 4500. 



1 Compt. Rend., 102, 1005 (1886). 2 Ann. Chini. Phys., 19, 2-44 (1900). 



