221 



during warm w.-.it hT, but not the laevogyratory salt. It happens 

 in ni.uiy . ases, that if a substance can be fermented both by cmulsine 

 ami by inrcrtuse, the behaviour of both enzymes towards the antipodes 

 is just opposite. Whether this may b<- <-<>ii>i<lnv<l to be a general 

 rulr, is not sure. Fischer stated that all enzymes fermenting maltose, 

 m the same way on ot-glucosides l ). 



Of course the disadvantage of this method of fission is that half 

 of the material is destroyed, only one of the optically active com- 

 ponents being preserved. Moreover the substances must be such 

 that living organisms can grow in their solutions, while just because 

 of the exclusively selective action, it is often a difficult matter to 

 find the right organism to effect the desired separation. 



11. Although in the next chapter we shall return to the details 

 of the method, a few words must again be said on a fission-method, 

 as used by some investigators, which is founded on the differences 

 in the velocity of formation or decomposition of compounds of the 

 types Af and A'f. 



Marckwald and Mac Kenzie 2 ) succeeded, after a number of 

 unsuccessful experiments of other investigators 3 ), in demonstrating 

 that if a,-ethoxy-propionic acid, racemic mandelic acid, etc., be com- 

 bined with l-menthol to form an ether, and if the reaction be stopped 

 after a certain lapse of time insufficient to finish the change com- 

 pletely, the acid set free from the ether by saponification was 

 endowed with rotatory power. 



The same appeared to be the case if racemic mandelic acid were 

 heated with l-menthyl-amine, so as to form the corresponding amide. 

 In the portion which was not changed into amide, an excess of 

 the laevogyratory acid was found to be present. It should be noted 

 that the compound which was formed more rapidly by etherification, 

 appeared also to be more rapidly decomposed by saponification, 

 which is in accordance with the fact that we have to deal here with 

 a reversible action, leading to a state of final equilibrium. 



This fission of the racemoid is of course only a partial one. We 

 shall return to this subject in the next chapter, when we are 



1) E. Fischer, Zeits. f. physiol. Chemie 26. 69, 79. (1898). 



2) W. Marckwald and Mackenzie, Ber. d.d. Chem. Ges. 82, 2130. (1899); 

 84. 469. (1901); W. Marckwald and R. Meth, Ber. d.d. Chem. Ges. 88. 

 801. (1905). 



) L.Simon, Bull, de la Soc. Chim. (3). 11. 760. (1894); P. Frankland and 

 Th. S. Price, Journ. Chem. Soc. London, 71. 253. (1897); etc. 



