200 



of chemical science which now is commonly indicated by the name 

 of stereochemistry 1 ). 



Pasteur 2 ), as a consequence of his work on this "molecular dis- 

 symmetry", soon put the question to himself: are the atoms of the 

 righthanded compound to be considered as grouped on the spirals 

 of a dextrogyratory helix, or as placed at the summits of an irregular 

 tetrahedron? Both views involve arrangements which are non-super- 

 posable with their mirror-images. However the last step necessary 

 to lead to the general conception of the "plurivalent asymmetric 

 atoms", was not made by him. It was Van 't Hof f 3 ) and Le Bel 4 ), 

 who in 1 874 simultaneously and independently of each other formu- 

 lated the important generalisation of the asymmetric carbon-atom, 

 at once making it possible to extend over the whole domain of organic 

 chemistry Pasteur's fundamental views on the special configu- 

 ration of the atoms. As we shall see, Pasteur's statement of the 

 case is, however, more general than that of the theory of Van 

 't Hoff and Le Bel. 



It is to Pasteur's genius moreover, that we are indebted for 

 the general methods now in use for the fission of racemoids into 

 their optically active components 5 ). They were the result of his 

 splendid and continual investigations during more than a full decade. 

 Before we go further into the conclusions of general significance, 

 to which the various facts gathered in this way have gradually led, 

 it seems better to deal more in detail with these various methods 

 of fission, and to consider at the same time the most important 



1 ) The innumerable investigations on the rotatory power of organic molecules, 

 its dependence on concentration, temperature, wave-length, chemical constitution, 

 etc. are not considered in detail in this chapter, although some data are occasionally 

 given for the purpose of illustrating other facts. For a full treatment of these 

 phenomena the author must refer the reader to the original papers of Th. S. 

 Patterson, P. Frankland, Ph. A. Guye, P. Walden, H. Rupe, and many 

 others; the results are dealt with e. g. in: H. Landolt's "Das Drehungsvermogen 

 organischer Verbindungen", in C. A. Bischoff und P. Walden's: "Handbuch 

 der Stereochemie", in A. Werner's "Lehrbuch der Stereochemie" etc., and in 

 many fuller or more restricted textbooks on stereochemistry. 



2 ) L. Pasteur, Deux Lemons sur la Dissymetrie Moleculaire, professees devant 

 la Societe Chimique de Paris, (1860). 



3 ) J. H. van 't Hof f. Voorstel tot Uitbreiding der tegenwoordig in de Schei- 

 kunde gebruikte Struktuurformules in de Ruimte, (1874). 



4) J. A. Le Bel, Bull, de la Soc. Chim. de Paris, (2). 22. 337. (1874). 



5) L. Pasteur. Compt. rend. 36. 191. (1852); 51. 298. (1860); Ann. de 

 Chim. et Phys. (3). 38. 437. (1853); Deux Lecons etc. loco cit. 



