VELOCITY OF REACTIONS 



substance transformed at the same time in the 

 mixture of reacting substances, and if, therefore, 

 the concentration of only this substance varies, 

 whilst the other substances remain unchanged, 

 the mathematical law of the process is quite simply 

 found. The velocity of such a reaction must 

 directly depend throughout the reaction on the 

 acting quantity of the substance. Since this 

 acting quantity of the substance is constantly de- 

 creasing, we see that the velocity of the reaction 

 cannot remain the same. It must diminish in a 

 certain ratio. Suppose 20 parts out of 100 are 

 transformed in the first minute, then there remain 

 in the second minute only 80 parts : 

 100100x0-2=80. 



We find for the process in the third minute the 



same : _ 



8080x0-2=64 



In the fourth minute : 



6464x0-2=51-2, etc. 



When we introduce for 100, which is the concentra- 

 tion at the beginning of the reaction, the general 

 symbol C , and for 80, 64, 51-2, etc., subsequently 

 C p C 2 , C 3 , . . : C t , and for the constant factor 

 0-2 the symbol k, the equations are : 



C Q -C Q k=C 1 or C (i-k)=C 1 

 further 



C (i-k)-C Q k (i-k)=C 2 

 or C (i &) 2 =C 2 



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