•_'-Jii Van Name and Bos worth — Rates of Solution of 



reduce the available surface of the disk, and second, the break- 

 ing off of the bubbles would stir the diffusion layer, thus 

 bringing the strong outside solution into direct contact with 

 the metal. These two effects would act in opposite directions, 

 but apparently the second predominates, for the constants 

 obtained are high. 



An experiment in the presence of 0*1 normal sulphuric acid, 

 giving a brisk hydrogen evolution, resulted as follows ; 



A. 8-72 9-28 8-50 8-43 Average 8-73 



In neutral solutions the disk remains free from hydroxide 

 if a little ammonium chloride is present, but even under. these 

 conditions there is a very marked evolution of hydrogen. 

 The two following experiments were performed in neutral 

 solutions whicli were about 0*025 . normal with respect 1 to 

 ammonium chloride : 



B. 9-31 



10-71 



11-85 



12-75 



9-50 





Av. 



10-82 



C. 9-19 



9-76 



10-06 



13-12 



7-50 



8-90 



Av. 



9-76 



The conspicuous irregularity of the constants is only what 

 would be expected when we consider the large effect which 

 would be produced by variations in the rate of formation or 

 in the size of the gas bubbles, factors which it is very difficult 

 to control. 



A number of experiments were carried out with aluminum 

 disks, but in every case the metal was so irregularly attacked 

 by the iodine that, no confidence can be placed in the results. 

 The disk after use was always found to be pitted with small 

 holes, witli intervening spaces which appeared to have been 

 attacked but little if at all by the iodine. The single experi- 

 ments gave fairly regular constants but duplicate experiments 

 did not agree at all closely. The values of the constants were 

 low in eveiw case except one, this being an experiment in the 

 presence of normal hydrochloric acid which gave an evolution 

 of hydrogen and a high constant, no doubt on account of the 

 hydrogen. In the other cases the acidity was - 25 normal or 

 less. All of the results, however, were entirely compatible 

 with the conclusion drawn from the inspection of the disks ; 

 namely, that a part of the surface of the metal was not attacked. 



Cadmium in the Presence of Varidus Iodides. 



It has been shown by Jakowkin* that iodine dissolved in a 

 large excess of an iodide of an alkali or alkali earth metal in 

 water solution is almost completely combined in the form of 

 triiodide. We should expect, therefore, that the diffusion of 

 iodine in such a solution would be determined chiefly by the 



*Zeitschr. phys. Chein., xx, 19. 



