482 UNIVERSITY OF VIRGINIA PUBLICATIONS 



The fact that the reaction velocity increases so markedly with increas- 

 ing concentration of potassium iodide at once aroused interest, for it was 

 not to be expected, and it did not accord with the diffusion theory of 

 reaction velocity in so far as known facts went. (This point gives us the 

 starting point for our present work.) 



When we remember how far apart the metals in question are in the 

 potential series it becomes impossible to ascribe the foregoing results to 

 purely local cell effects, as has been done by Wildermann and other critics 

 of this theory. We should bear in mind that the close duplication of 

 results constantly shown by the data of Van Name and Edgar remove the 

 possibility of mere accidental coincidence, which has been claimed to be 

 the explanation of some data given by previous investigators to prove the 

 same theory. Van Name and Edgar thus summarize their work: 



1. "The rates of solution of the metals Hg, Cd, Zn, Cu, and Ag, in 

 aqueous iodine solutions containing a large excess of potassium iodide 

 have been measured at 25° and shown to be practically equal, a sUght 

 difference observed with copper and silver being in all probability due to 

 accumulation of the solid iodide at the contact surface." 



2. "The temperature coefficient for 10° (between 25° and 35°) is about 

 1.3." 



3. "An increase in the concentration of the potassium iodide produces a 

 marked acceleration of the reaction." 



4. "Mercury dissolves in bromine in the presence of potassium bromide 

 slightly faster than in iodine, but in cupric bromide much more slowly. . . " 



5. "The reaction was found to be proportional, on the average, to the 

 I power of the rate of stirring." 



6. "So far as can be decided from the data at present available, the 

 diffusion theory of Noyes, Whitney, and Nernst, gives a satisfactory 

 explanation of the results obtained." 



It will be noted that the fact hardest to reduce to terms of the diffusion 

 theory is that an increase in the concentration of the potassium iodide 

 causes marked acceleration in the rate of the reaction. 



Work of Van Name and Bosworth (13). Later Van Name and Bos- 

 worth worked with iron, nickel, and cobalt, in addition to those metals 

 used by Van Name and Edgar. The fact that these metals also react 

 with iodine at very nearly the same rate as those previously discussed 

 adds greatly to the probability of the diffusion theory. The following 

 quotation from the work of Van Name and Bosworth is of interest here. 



The agreement between the metals Cd, Fe, Ni, and Co, is very striking, and 

 clearly proves that under like conditions these metals dissolve in iodine at the same 



