252 Van Name and Edgar — Velocities of Certain Reactions: 



Table XI. 

 Influence of Eate of Stirring. 



Metal 



Table 



Experiments 



, 



rr 









n 



Hg 



I 



1 



& 



2 



6-43, 



8-81 



0-91 





I 



3 



& 



5 



7-21, 



9-55 



0-82 





I 



4 



& 



6 



8-54, 



11-12 



0-74 





I 



7 



& 



8 



8-14, 



10-48 



0-73 



Ou 



II 



1 



& 



2 



7-95, 



9-98 



0-66 



Ag 



III 



1 



& 



2 



8-23, 



9-93 



0-65 



Cd 



IV 



1 



& 



2 



6-36, 



8-69 



0-90 



Zn 



V 



1 



& 



2 



7-03, 



8-64 



0-75 



Hg in CuBr 2 



IX 



1 



'& 



2 



4-93, 



6-30 



0-83 



The values of n for copper and for silver are the lowest in 

 the table. Except for these the agreement is about as. good 

 as could be expected ; first because n is in all probability not 

 a constant but variable with the conditions of concentration, 

 etc., and second because n, for mathematical reasons, is rather 

 sensitive to variations in K. 



The effect upon the reaction velocity of doubling the con- 

 centration of the potassium iodide is shown in Table XII, 

 where the ratios of the constants are given for such pairs of 

 experiments as differed only in this respect. Here again 

 copper shows a distinct difference in behavior from the other 

 metals, silver not being represented in the table. The differ- 

 ence is unexpectedly large, but in the absence of other data 

 to confirm it, nothing more than a qualitative significance can 

 be attached to this single result. 



Table XII. 

 Influence of Concentration of Potassium Iodide. 



Metal 



Table 



Experiments 



, 



■K , 



Eatio 



Hg 





3 & 1 



7-21, 



8-43 



1-12 







5 & 2 



9-55, 



8-81 



1-08 







7 & 3 



8-14, 



7-21 



1-33 







8 & 5 



10-48, 



9-55 



1-10 



Cu 



II 



3 & 2 



10-27, 



9-98 



1-03 



Cd 



IV 



3 & 2 



9-56, 



8-69 



1-10 



Zn 



V 



3 & 2 



9-64, 



8-64 



1-12 



These comparisons serve to emphasize both the close agree- 

 ment in the reaction velocities of mercury, cadmium and zinc, 

 and the consistent though usually small deviations shown by 

 copper and silver. The latter, however, are all explainable 

 upon the assumption that the reaction is retarded to a slight 

 extent by the presence of traces of the solid iodide at the 

 contact surface. This explanation is a probable one and in 

 the opinion of the writers may reasonably be accepted. ¥e 

 may conclude, in other words, that not mercury, cadmium, 



