286 ORGANIC CHEMISTRY 



little value except to check the accuracy of the analyses and as a sim- 

 ple expression for empirical composition. I need not dwell on the 

 confusion which existed throughout the first half of the century be- 

 cause there was no agreement as to the basis for molecular weights 

 or atomic weights, nor upon the large part played by the study of or- 

 ganic compounds in finally clarifying the view of chemists upon these 

 matters. Yet, in spite of this confusion, two discoveries of funda- 

 mental 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 certain groups of atoms may remain 

 together in passing from one compound to another through a whole 

 series. The first fact furnishes 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 superficial. 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 : x "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 typi- 

 cal formula? were so easily transformed into structural formulae when 

 the fact of valence was once grasped, cannot 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 scaffold- 

 ing. 



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 electro-chemical theories held at the time and which 

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



