between Metals and Dissolved Halogens. 255 



accounts for the results obtained, and so far as yet shown leads 

 to no inconsistencies, would seem to justify its retention for 

 the present in dealing with reactions of this class. The work 

 will be continued along similar lines. 



Summary. 



1. The rates of solution of the metals mercury, cadmium, 

 zinc, copper, and silver, in aqueous iodine solutions containing 

 a large excess of potassium iodide, have been measured at 25° 

 and shown to be practically equal, a slight difference observed 

 with copper and silver being in all probability due to accumu- 

 lation 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, the ratios of the velocities being about 

 12-3 : 11-0 : 6-9. 



5. The reaction velocity was found to be proportional, on 

 the average, to the 4/5 power of the rate of stirring. 



6. So far as can be decided from the data at present avail- 

 able, the diffusion theory of Noyes, Whitney, and Nernst 

 gives a satisfactory explanation of the results obtained. 



