Solutions of Iodides under the Influence of Actinism, 91 



Effect of Starch on the Bate of Change {March 18, 1879). 

 Brilliant Sun, 





1.30 



-2.30 p.m. 



2.30-3.30. 



3.30-4.30 



Eeagents. 



5 cub. centiins. 

 starch-water. 



30 cub. centims. 

 starch. 



No starch. 



H 2 S0 4 + KI 



, 



0-48 



0-51 



1-65 



HC1 + „ 



. 



1-18 



1-46 



3-50 



HN0 3 + „ . 



, 



3-10 



2-57 



3-50 



H 2 S0 4 + CdI 2 



, 



0-49 



0-82 



1-65 



HC1 + „ 



, 



1-90 



1*11 



3-55 



HN0 3 + „ 



, 



2-80 



2-83 



3-40 



H 2 S0 4 + LiI 



, 



0-34 



0-40 



0-30 



HOI + „ . 



t 



0-59 



0-72 



1-75 



HNO3 + „ 



, 



2-7 



3-86 



2-75 



H 2 SO, + KI 



• • 



0-48 







March 19. 



12 



(noon)-l 3 



?.M. Feeble Sunlight. 



H 2 S0 4 + KI 



, 



0-26 



... 



1-8 



HOI + „ 



, , 



0-40 



... 



2-4 



H 2 S0 4 + CdI 2 



, . 



0"22 



... 



1-6 



HC1 + „ 



. 



0-40 



. . . 



2-2 



H 2 S0 4 + LiI 



. 



0'20 



... 



1-2 



The experiments of March 18, performed as they were with 

 a sun approaching the horizon, having been less decisive than 

 could have been desired, they were repeated on the following 

 day, but with the disadvantage of a feeble sunlight, with the 

 result of showing that six times more iodine was set free in 

 the absence than in the presence of starch. The suspended 

 precipitate of starch iodide cut off the light, except upon the 

 superficies of the solution. Henceforth the employment of 

 starch was abandoned. 



The next set of trials was instituted in order to observe the 

 influence, upon the rate of change, of larger access of oxygen 

 than that derivable from the air already dissolved, or in con- 

 tact with the solution at its upper surface. To this end tests 

 were prepared in duplicate ; and through one pair of these 

 duplicate solutions, the comparison-tubes being connected 

 together in the manner of wash-bottles, a slow current of 

 oxygen was passed. 



H2 



