of Chemical Change. 447 



such an experiment and of one where no such substance is 

 present excepting what is formed during the reaction. 



If the initial quantities A 1? A 2 , . . . A n are in equivalent 

 proportions, they may be expressed in terms of A K , thus 

 A 1 = e 1 A /c . . . A n =e w A K . But suppose for the most general 

 case that they are multiples of these quantities, or A x = v^ k K . . . 

 A n = v n e n A K ; a u a 2 , • • • a n> however, are always in equivalent 

 proportions, or u ] = e^* . . . a n = e n c*. K . Substituting these values, 

 \l) becomes 



d"< = ^(vi€iA K — e x ci K ) . . . (A K — a K ) . . . (v n e n K - e n cL K ) 



dt B + Ct K (X^i + X 2 € 2 . . . + X n € n ) 



Writing A K — <x K =y, the amount of A K that remains active at 

 time t, and -~ = — -~. This equation may be written in the 

 form 



di__ gy{(vi-l)A+y} |(r a -l)A+y} ...{(yn-\)K+y\ m 



dt ' b+y ' K } 



The reaction under consideration (the oxidation of ferrous 

 chloride by potassic chlorate) is represented by the equation 



6FeCl 2 + KC10 3 + 6HCl=3Fe 2 Cl 6 + KCl+3H 2 0; 



and consists of a system of three active members, in which the 

 iron, or y, was made the subject of measurement. In the 

 preliminary experiments that were made, the ratios of the 

 chlorate and acid to the iron were varied, in order to find the 

 quantities, and consequently the rate, of the oxidation most 

 suitable for bringing out the retardation-effects of the chlorides. 

 Some experiments were made w 7 ith all three materials in equi- 

 valent quantities which would be represented by the equation 



d y = . a y z . 



dt " b+y 



But such conditions were unsuitable ; for the experiments 

 show r ed, as is evident from this equation, that, as the rate 

 varies as the third power of y, at the start the reaction pro- 

 ceeds very rapidly, and quickly becomes very slow, a state of 

 matters most inconvenient for the purpose in view. It was 

 ultimately found best to employ different multiples of equiva- 

 lents of acid and chlorate for the different purposes of studying 

 retardation of sulphates, of chlorides, and influence of tempe- 

 rature, as given below. 



The preliminary experiments with the chlorides showed 



