26 



Studies on Solution. 



The A c curves for wave-lengths 605^ju to 764/>(/z, inclusive, lying 

 on the edge of the yellow-green band, show that A decreases in a 

 marked manner with dilution and reaches a minimum value at about 

 c = 1 .0. Below c = 1 .0, A shows a slight increase. 



The A c curves for those wave-lengths in the region of transparency, 

 from 842/i^t to 979/z/i, are straight lines parallel to the abscissse, show- 

 ing that A in this region is constant for all concentrations. For wave- 

 lengths greater than 979,u/i, which lie on the edge of the infra-red band, 

 A is a constant within the error of experiment. The two band-edges in 

 question are thus seen to behave quite differently as dilution proceeds. 



Houstoun 1 has drawn the absorption curves for two solutions of cobalt 

 chloride in water, and table 5 shows the comparison between his values 

 and the values interpolated from table 4. 



TABLE 5. .4 for Cobalt Chloride in Water. 



The agreement between Houstoun's values and the values of A found 

 in the present investigation is far from satisfactory. However, both 

 sets indicate similar changes in A with c. 



COBALT CHLORIDE IN METHYL ALCOHOL. 



Seven solutions were prepared varying in concentration from 

 c = 0.7 to c = 0.1. The solutions appeared to keep very well, and no 

 such precipitate was formed as was noticed in the aqueous solutions. 

 The absorption curves show that the character of the absorption of 

 the alcohol solutions was quite different from that of the aqueous 

 solutions, the absorption curve for the alcohol solution being shifted 

 towards the red, so that the minimum of absorption was now at 842ju/z, 

 the shift thus amounting to about SOjuju. The shift towards the red of 

 the edge of the band in the green was sufficient to make this band 

 absorb nearly all of the visible red light. (Instead of speaking of the 

 "shift of a band," some have preferred to speak of the bands in the 



. Roy. Soc. Edinburgh, 31, 521 (1910-11). 



