37 



phase. Now follows i in mediately another qnestion, viz. may in this 

 case an equation of velocity be applied which holds good for a 

 solntion? As Nf.knst ^) has observed an eqnation of velocity iiolding 

 for a homogeneons system leads to an entirely wrong conclnsion in 

 a helerogeneons system, when the velocity of reaction is dependent 

 on the velocities of difTnsion. This will always be the case where 

 the velocity of reaction is great with respect to the velocity of 

 diffnsion. 



When, however, on the contrary in a heterogeneons system the 

 concentration ecpiilibrinm sets in rapidly, and the reaction proceeds 

 comparatively slowly, the influence of the difTnsion velocity is only 

 slight, and can become quite imperceptible. This now is generally 

 the case when both phases are liquid When a substance ^ dissolved 

 in a solvent B is shaken with a solvent C, which does not mix 

 with B, only a very short time is required to establish the equili- 

 brium between the two solutions. 



H. GoLDscHMiüT ') has determined the velocity of saponification 

 of ethyl acetate dissolved in benzine and shaken with about nor- 

 mal hydrochloi'ic acid. Assuming that the reaction takes place in 

 the aqueous solution he represented the velocity of saponification by 

 the equation : 



dx V, . C 

 = K. — ' x. ...... (1) 



(it v^-\- v^ . C 



in which )\ = volume of the a(|neous solntion, v^ = volume of the 

 b(;nzolic solution, C= constant of partition of ethyl acetate between 

 water and benzene. On the whole the reaction velocity appeared to 

 be well represented by this equation. 



Towards the end, the reaction in the opposite sense had to be 

 taken into account. 



It appears from this that when the velocity of reaction is not too 

 great, the ecpiations of velocity which hold in a homogeneons system 

 may be applied in a heterogeneous system, consisting of two licpiid 

 phases. 



Let us now return to the saponification of fat, and let us imagine 

 the case that a triglyceride is saponified with diluted sulphuric 

 acid according to the Twitchfli, process, in which fat and aqueous 

 solution is held in emulsion by blowing in of steam, after addition 

 of about V, 7o TwiTCHKLL reagent. Goldschmidt's formula may cer- 

 tainly not be used in this case for quantitative determinations. For 



1) Z. f. phys. Ghem. 47 55 (1904). 



2) Z. f. phys. Ghem. 31 235 (1899). 



