No. of 

 Exp. 



1. k =. 



Metal : 

 3-75 



Nickel, 

 375 



2. ib = 



3-82 



(lost) 



3. k = 



3-86 



3-54 



4. k = 



3-24 



3-19 



5. * * - 



171 



1-69 







K 



3-33 



2-98 



341 



3-18 



3-15 



336 



3-22 



311 



342 



306 Fan Name and Hill — Solution of Metals 



Nickel. — Table III contains the results of the experiments 

 with metallic nickel. Two samples of "pure nickel" were 

 used, one furnished by Kablbaum, the other of unknown ori- 

 gin, both of which seemed to give practically the same results. 

 The former was used in Experiments 1 and 2, the latter in 

 Nos. 3, 4, and 5, and also in the experiments with chromic 

 acid, to be described later. 



In no case was the action of the solution on the metal per- 



Table III. 



R'Fe(SO.,) 2 , 005 molar. > 



H 2 SOi, 0-01 molar. 



3-53 3-29 327 

 H 2 S0 4 , 025 molar. 



3-53 336 3-15 



3-49 3-42 3-31 

 H a S04, 1-25 molar. 



3-07 2'93 2-89 2'82 278 299 



H2SO4 , 5 molar. 



156 152 1-49 1-45 T45 1'55 



Initial velocities by extrapolation : Exp. 1, 3*80 ; Exp. 2, 375; Exp. 3, 375; 

 Exp. 4, 3-27; Exp. 5, 171. 



fectly normal and uniform. In the presence of # 01 and 0*25 

 molar sulphuric acid distinct black coatings formed on the 

 disk, while even at the highest acidity, 5 molar, the disk 

 acquired a brownish discoloration and, ultimately, a minutely 

 spotted appearance. Examined under low magnification these 

 spots were seen to consist of irregular rounded hollows, each 

 containing traces of a brown deposit. 



As the probable result of these irregularities in the action, 

 we find in all cases that the velocity constants decrease as the 

 experiment progresses, though less rapidly in the more strongly 

 acid solutions. However, the constants for each single experi- 

 ment, when plotted with time as the other coordinate, lie fairly 

 close to a straight line, so that by extrapolating this line back 

 to time zero we obtain a corrected value for the reaction veloc- 

 ity which represents, at least approximately, the rate at which 

 the reaction would proceed under the given conditions if the 

 sources of disturbance were absent. The initial reaction veloc- 

 ity for each experiment, as obtained by such extrapolation, is 

 recorded at the foot of the table. Although, owing to irregu- 

 larity in the constants, this procedure sometimes fails to give 

 sharp results, these extrapolated values are certainly more accu- 

 rately and fairly representative of the single experiments, in 



