280 



and if the reaction, before complete, be stopped at a well-chosen 

 moment, it will turn out that unequal quantities of ABandA'B 

 will be produced during that lapse of time, and thus, if the 

 mixture AB + A 'B be isolated and B removed from it, the sub- 

 stance obtained A A' will be no longer optically wactive, but 

 will show a positive or negative rotation, because there is now 

 some excess of one of the antipodes A or A'. Of course, if the 

 original compound A A' which has not yet combined with B, be 

 examined now, it will also show an optical activity which is 

 opposite to that found with the portion of A A' attacked, because 

 there is now an excess of the other antipode A' or A in the mixture. 



It has been stated in a few cases 1 ) that the chemical affinity 

 of both enantiomorphous molecules of the same compound, is 

 the same, even towards an optically active compound. 



Thus Fischer 2 ) observed that there is no difference in the 

 inversion-velocity of cane-sugar by dextro- or /aewgyratory cam- 

 phoric acid. As the inversion-velocity is directly proportional to 

 the concentration of the .ff-ions, this result cannot astonish us. 

 The same appeared to be the case if saccharose were hydrolysed 

 by d-, and /- camphor- (3-sulphonic acids. 3 ) 



The two antipodes of an active acid will also divide an opti- 

 cally active base equally between them: in the end there will 

 be 50% of the one salt and 50% of the other, if only the quantity 

 of the added base be sufficient to neutralize the acid, and the 

 reaction have time to reach its final equilibrium. 



6. A question of importance is: will there be a difference 

 in the reaction-velocity of two antipodes when the reaction takes 



between A' and B, need not exclude the possibility of unequal reaction-velocities 

 in both cases. In the reactions: 



A + B ~^ AB, and: A' + B ~^ A'B, 



the velocities are characterised by the velocity-constants k and j', and k 2 and 

 k' z . The affinities however are expressed by a relation of the form : RTlnK, 

 in which the equilibrium-constant K is the same for both reactions and equal to 

 k-, ft 



TT r t0 T^- 

 ft 1 2 



Now (k^ k\) and ( 2 - ' 2 ) can be very well different from each other, while 

 the quotients are in both cases the same. 



1) W. Marckwald and A. Chwolles, Ber. d. d. Chem. Ges. 31. 783. (1898). 



2) E. Fischer, Ber. d. d. Chem. Ges. 32. 3617. (1899). Cf. also: W. Marck- 

 wald and A. Me. Kenzie, ibid. 33. 208. (1900). 



3) R. Caldwell, Proceed. Roy. Soc. London, 74. 184. (1904). 



