Reaction before Complete Kquilibrium. 487 



In conclusion, those few experiments which have been 

 undertaken at different times by different investigators with 

 the object of finding out the laws of the velocity of chemical 

 reaction in heterogeneous systems may be mentioned. De la 

 Rive (1830), Boguski (1876), Kajander (1881), have investi- 

 gated the velocity of solution of metals in acids, but could 

 not arrive at any simple relations. Boguski attempted then 

 to solve the same problem by an investigation of the velocity 

 of reaction of acids (HC1, HBr, N0 3 H) upon Carrara marble 

 (1877), and he found that the equation 



^ = KO(a-*) 



ar v ' 



holds tolerably well (where is the surface of the solid 

 m-irble, a — x is the concentration of the acid). His formula 

 cannot be true, not only for reasons given above, but it con- 

 tradicts the laws of action of mass. Our system in this 

 case is : — 



Zn in sol. + 2HCl^ZnCl 2 in sol. + H 2 in sol. (saturated) 



jorf _ \ 



Zn solid. H 2 gas (escapes). 



CaC0 3 in sol. + 2HCl^CaCl 2 in sol. + CO, in sol. (saturated). 



\ or \ I 



CaC0 3 solid. C0 2 gas (escapes). 



For solid CaC0 3 (solid Zn)-H>r<-CaC0 3 in solution (or zinc in 

 solution) we have : — 



dt 



(£)=C$r(po~Pr). 



For CaC0 3 in solution + 2HC1 in solution^ CaCl 2 in solution 

 + C0 2 in solution, as well as for Zn in solution +2HC1 in 

 solution "*" ZnCl 2 in solution +H 2 in solution, we have : — 



dt 



(^y^c^.yCcV.K, 



or if the opposite reaction be neglected : — 

 (dt 



£} 



C'pr ./ 2 . 



Now just as many molecules Zn in solution (or CaC0 3 in 

 solution) must in the unit of time transform into ZnCl 2 

 (or CaCl 2 )and H 2 (C0 2 ) as molecules of the solid Zn (CaC0 3 ) 



