BETWEEN THE CONDITIONS OP A CHEMICAL CHANGE AND ITS AMOUNT. 209 



that the relation indicated by theory did, under some circumstances, actually hold good. 

 The numerical results of this experiment are compared below with the values o£y calcu- 

 lated from the equation y=94'8(*974)', and are represented by a curve on Plate XVII. 

 fig. 5. 



Table IX. 



K2 Mn2 08+14Mn S O4+IO8H2 C^ O4. 



Volume of solution 200 cub. centims. Temperature 16° C. Time x mins. 



Generally the reaction appeared to proceed more slowly in its later as compared with 

 its earlier stages than on this hypothesis it ought. It seemed possible that this might 

 arise from the excess of the various reagents employed not having been sufficient to 

 prevent the action producing a sensible alteration in the nature of the solution, and 

 thus affecting the rate ; for unless the amount of each of the other substances be so 

 great as compared with that whose rate of diminution is measured that the quantity 

 subtracted from or added to them is relatively insignificant, the simplicity of the case 

 under examination is no longer ensured. Accordingly a second set of experiments was 

 made, in which, the amount of permanganate employed being the same, a still larger 

 proportion was used of the other reagents; and by making two preliminary series of 

 experiments, in one of which the same quantity was taken at the beginning of the 

 reaction as had been present in the othet- at the end, namely, 99 proportional parts 

 of sulphuric acid and oxalic acid, instead of 100 of each, and 11 parts of manganous 

 sulphate, instead of 10, it was proved absolutely that these changes did not afiect the 

 rate, for the numbers of the two series were nearly identical. 



The numerical results of this set are contained in the following Table, and are 

 expressed by the curves (Plate XVIII. fig. 2). 



MDCCCLXVI. 



2g 



