272 Dr. Meyer Wilderman on the Velocity of 



reactions before complete equilibrium follows the same general 

 law 



^=U(* P -0(*-*a*4-K), 



we are now entitled to regard all those reactions as being of one 

 and the same nature. If it be further considered that in the 

 establishing of all the different hinds of equilibrium there is 

 always a cooling or warming of the system by the surrounding 

 medium, it becomes evident that not only have we to deal with 

 real and apparent freezing-points, but also with real and 

 apparent vapour-pressures, sublimation-pressures, boiling-points, 

 solubilities, fyc. In all these cases one of the two opposite 

 reactions (evaporation, sublimation, solution, or condensation 

 to liquid or solid, separation of the solid from supersaturated 

 solutions, &c.) comes into consideration according as the 

 convergence temperature is above or below the point of 

 equilibrium. This equation must necessarily be connected 

 with that of cooling or warming of the system by the sur- 

 rounding medium. Ihe general equation is in all cases 



<^=:C'(t o -t)(t-t ov + K) +C(t g -t), 



when during the reaction the surface of contact of the solid 

 with the liquid or the gas varies (in the case of freezing- 

 points, solubility, &c); or 



|=c"(to-*j+c(«,-o, 



when the surface of contact remains constant (vapour-pres- 

 sures, boiling-points, &c). When ~r becomes = 0, we get 



az 



not the reed, but an apparent point of equilibrium. The apparent 

 point of equilibrium is always obtained between the real point 

 of equilibrium and the convergence temperature. It is above 

 or below the real point of equilibrium, according as the con- 

 vergence temperature is, at the given arrangements of the 

 experiment, above or below the real point of equilibrium. 

 The difference between the real and apparent equilibrium, or the 

 error of the observed results, depends upon how far we suc- 

 ceed by the given arrangements of the experiment in keeping 

 the latter fraction as small and as constant as possible in the 

 equation T' (observed apparent point of equilibrium) = T (the 

 real point of equilibrium) 



+ : cfc-o 01 . , m,- t ) 



C'(t c -t m .+K) + C" 



