Mr. J. J. Hood on the Laics of Chemical Change. 379 



determined by making a solution of iron containing *4923 

 grm. Fe in 295 cubic centims. water and titrating 10 cubic 

 centims. with the permanganate used in the experiment; its 

 value was found to be 10*36 cubic centims., the values of?/ 

 being, as before, the number of cubic centims. of permanga- 

 nate required for 10 cubic centims. of the experimental solu- 

 tion. 



The first observation, at £ = 0, gave y= 9*45 cubic centims. ; 

 and when £ = 30'5 units, y=7*30 cubic centims. Taking 

 equation (8), 



1 \( (n-l)k + a \\ 



^ + ( n _i)AA a Jy 



and inserting those values, using the second observation to 

 find C, we get 



The values of t are calculated from this equation (in 

 minutes), using the observed values of ?/, and are compared 

 with those observed. The close agreement between theory 

 and experiment is very striking. 



Temperature 18° C. n = 2. 



-<= C MC-T(^X ! 



Permanganate, in 

 cubic centims. 



Time, in minutes. 



Found. 



Found. 



Calculated. 



9-45 

 7-30 

 5-98 

 4-74 

 4-06 

 3-30 

 2-63 

 2-30 

 1-93 

 1-58 

 1 14 

 •98 







30-5 



55 



89 



112-2 

 143-2 

 180-5 

 206-8 

 237-5 

 272 

 336-3 

 360 



56-4 

 89- i 

 112-6 

 144-8 

 182-5 

 205 5 

 236-5 

 273 

 334-4 

 3637 



Experiment (j3). — Every thing the same as before, except the 

 ratio of the iron to the potassic chlorate, viz. 1 : 3, or n = 3, and 

 total volume 300 cubic centims. The value for A was found 

 to be 10*18 cubic centims. ; and taking the first two observa- 

 tions for a and C, we get 



— -"'-•{UmXSS)}- 



The results are given below. 



