OCTOBEE 14, 1904.] 



SCIENCE. 



491 



ters which interest us most are concerned, 

 there was practically no knowledge of or- 

 ganic chemistry before the nineteenth cen- 

 tury. The first steps were, of course, the 

 preparation of pure substances and the de- 

 velopment of accurate methods of analysis. 

 In both of these fields Liebig was the 

 great master. The formulse which were 

 calculated were, at first, of little value ex- 

 cept to cheek the accuracy of the analyses 

 and as a simple expression for empirical 

 composition. I need not dwell on the con- 

 fusion which existed throughout the first 

 half of the century because there was no 

 agreement as to the basis for molecular 

 weights or atomic weights nor upon the 

 large part played by the study of organic 

 compounds in finally clarifying the view 

 of chemists upon these matters. Yet, in 

 spite of this confusion, two discoveries of 

 fundamental importance date from this 

 period: (1) That the empirical composition 

 alone does not fix the nature of a compound, 

 i. e., the fact of isomerism; (2) that cer- 

 tain groups of atoms may remain together 

 in passing from one compound to another 

 through a whole series. The first fact fur- 

 nishes one of the strongest reasons why an 

 empirical formula for an organic compound 

 is not enough, and the second fact furnishes 

 the most important experimental basis at 

 the foundation of our structural formulae. 

 The studies of this period furnished a 

 knowledge of the empirical composition of 

 many natural products and of the products 

 obtained from these by oxidation, reduction 

 and the action of various agents. But 

 while some might, perhaps, be inclined to 

 look upon this mass of empirical knowledge 

 as the most valuable acquisition of that 

 time and to think that the theories in vogue 

 were so imperfect or erroneous as to be of 

 no value, such a view is certainly super- 

 ficial. There were plenty of chemists in 

 that day, too, who were ready to decry 

 theories which seemed to them worthless. 



and it is interesting to read to-day what the 

 great Laurent said upon this matter. He 

 wrote in 1837 :* "If I could believe that 

 the purpose of my work was only to find a 

 few new compounds or that it would end 

 in my being able to say that there is an 

 atom more or less in this compound or that, 

 I would give it up on the spot. Only the 

 desire of finding an explanation for some 

 phenomena and of proposing some more 

 or less general theories can give me the 

 courage to follow a course in which I have 

 found so little encouragement and where 

 I have met with so many obstacles to over- 

 come." Any one who has followed the 

 story of how the older theories of radicals 

 paved the way for the theory of types and 

 of how the typical formulae were so easily 

 transformed into structural formulae when 

 the fact of valence was once grasped, can 

 not fail to see that the larger and fuller 

 view is an outgrowth from the earlier 

 theories. And we must acknowledge that 

 Laurent was right and that the theories 

 upon which he was working were of vastly 

 more importance than the mass of empirical 

 facts which furnished him with their scaf- 

 folding. 



Do not misunderstand me. There were 

 two theories of radicals at that time— one 

 which devised radicals in the study which 

 should accord with the electrochemical 

 theories held at the time and which did not 

 attempt to secure evidence of their exist- 

 ence from the conduct of the compounds 

 containing them, another which kept in 

 much closer touch with the facts discov- 

 ered in the laboratory. It was only the 

 latter theory which contributed much to 

 the growth of our knowledge. A theory 

 which can not secure for itself a sound ex- 

 perimental basis is, of course, of only 

 ephemeral value. 



These^ then, are the steps which have led 

 to our present standpoint in organic chem- 



* Ann. d. Chem. (Liebig), 22, 143. 



