and the absorption spectra of various permanganates. 253 



. III. 



In order to test the accelerative effect of light, solutions of 

 permanganate of zinc were made ; one series in the light, and 

 allowed to stand in the full glare of the light of the laboratory, 

 and another series of solutions made in the dark and allowed to 

 stand well covered up with black cloth and placed in a cupboard 

 to which no light could penetrate. The solutions standing in the 

 light were examined by the eye from time to time. After six 

 hours a very slight change in the usual permanganate tint of the 

 310 solution was noticeable ; but none in the 154 solution. 

 After 10 hours standing the 154 solution was still pink and the 

 310 solution was rose coloured. On standing 24 hours, the 

 310 solution was light yellow brown in colour, and the 154 

 solution was rose red. The solutions appeared to retain this 

 colour during another 24 hours. 



After two days standing, the solutions which had been made 

 in the dark, and which had stood in the dark during this period 

 of time, were then examined and compared with those kept in the 

 light, and there appeared to be exactly the same changes in colour 

 in them. 



L. Zinc perraanaranate in dark } ^ ^a i i.- 



1 ^ J® • r 1 J. r 154 solutions, 



do. do. m hght J 



do. do. in dark 5 solution. 



Band 1 was not quite so wide in the 154 dark and light 

 solutions as in the 5 solution ; band 2 was also narrower in the 

 154 solutions; band 3 was also narrower but not so well marked ; 

 whilst bands 4 and 5 appeared to be slightly wider in the 154 

 dark and light solutions. The general absorption in the solutions 

 kept in the dark and in the light was about the same in each, 

 and greater than that of the 5 solution. Also there was a 

 slight shift of the bands in the 5 solution towards the red 

 end more than in the 154 solutions, but the difference was not 

 well marked. 



M. Zinc permanganate in dark 1 o-irv i j.- 

 do. do. in light J 



do. do. in dark 5 solution. 



Band 1 was again not so wide in the dark and light 310 

 solutions as the corresponding one of the 5 solution ; bands 

 2 and 3 were also much narrower in the dark and light solutions ; 

 whilst bands 4 and 5 appeared to be slightly wider in the dark and 

 light 810 solutions than in the dark 5 solution. 



The general absorption of light in the solution kept in the 

 light was a shade more marked than that kept in the dark ; 



