126 HISTORY OF CHEMISTRY. [LECTURE VII. 



impression which it produced at the time can be well under- 

 stood. It was the first instance where, starting from one 

 compound, an extensive series of well-defined substances had 

 been obtained, the relations of which could easily be explained 

 if the suggested mode of regarding them was adopted. We 

 thus find Berzelius, then at the zenith of his fame and only 

 seldom in accord with the views of others, bestowing abundant 

 praise upon the investigation. 52 He hopes that, as a conse- 

 quence of it, a new day will dawn in chemistry, and he proposes 

 to Liebig and Wohler to call the new radical Proin or Orthrin 

 (break of day) because he believes that a clearer light will 

 be cast upon our science by the assumption of ternary 

 radicals. 



And Berzelius was right ! For even although the chief 

 importance of the investigation does not rest with the radical 

 composed of three elements, still the special part which had 

 been universally attributed to oxygen since Lavoisier's time, 

 even in this branch of chemistry, was taken away from it. 

 Further, that the true signification of the word radical was to 

 be sought for elsewhere, was demonstrated by the fact that, in 

 the choice of a radical, the composition was left entirely out 

 of consideration ; and the justification of this proceeding was 

 found in the experimental results. Benzoyl was a radical be- 

 cause, like an element, it combined with other elements, and 

 because it could be transferred, without decomposition, from 

 the compounds so formed, into others. It was the key to the 

 interesting reactions of Liebig and Wohler, and it formed the 

 foundation of the benzoic acid series just as cyanogen was the 

 .basis of a large number of substances. 



Cyanogen and benzoyl are the pillars of the radical theory, 

 which received confirmation by the discovery of cacodyl. I 

 cannot enter into the details of this extremely difficult and 

 brilliantly executed investigation of Bunsen's, but it is my duty 

 to state the general results of his work. 



In 1760, Cadet had obtained a fuming liquid, possessing a 



82 Annalen. 3, 282. 



