Mr. J. J. Hood on the Laws of Chemical Change. 373 



the initial values of the bodies, a and j3 the amounts of A and 

 B that have already undergone change up to time' t, and let 

 Set be the amount of A acted on in time Bt ; then, by the above 

 hypothesis, 



S« = *(A-a)(B-£)8* (1) 



Suppose, further, that the amounts of A and B are chemi- 

 cally equivalent (that is to say, they are just sufficient to 

 render each other inactive), then the ratio 



A_a 

 B~£' 



call this -, and equation (1) becomes 



8u=fcv(A-u) 2 St (2) 



Replacing A— a by y, the amount of A that remains un- 

 acted on at the time t, 



I—"* < 3) 



which, on integrating, gives 



-=(C + KVt), 



or, writing it in the more convenient form, 



b=y(a + t), (4) 



being the equation to an equilateral hyperbola with axis t for 

 asymptote. 



The influence of temperature and the non-equivalence of A 

 and B I will consider further on, after I show how far expe- 

 riment agrees with this theory. 



Experiments. — In the first experiments made, not knowing 

 how the rate of change was influenced by heat, I took every 

 care to keep the temperature of the water-bath perfectly 

 constant ; but in spite of every attention, the fluctuations 

 were about ±*1° C. This, I afterwards found, could not in- 

 troduce any considerable error. The flasks containing the 

 experimental solutions were submerged in the bath, and were 

 never removed during the experiment. The solutions were 

 freely exposed to the air, as it was found, after repeated trials, 

 that atmospheric oxygen had not any perceptible influence on 

 them during the time the experiments lasted. 



The active bodies used were (1) a solution of ferrous sul- 

 phate containing an indefinite amount of hydric sulphate, 

 and (2) a solution of potassic chlorate, the strengths of which 

 were accurately known. 



