LECTURE XIII. 



IDEAS REGARDING THE TYPES ELUCIDATION OF THE NATURE OF THE 

 RADICALS BY THE VALENCY OF THE ELEMENTS QUADRIVALENCE 

 OF CARBON SPECIFIC VOLUME CONSTITUTIONAL P'ORMUL/E 

 SEPARATION OF THE IDEAS OF ATOMICITY AND BASICITY Iso- 

 MERISM AMONGST ALCOHOLS AND AdDS PHYSICAL ISOMERISM 

 UNSATURATED SUBSTANCES. 



IN the preceding lecture I showed how the views respecting 

 the different valencies of the radicals and elements attained a 

 great importance through the labours of Williamson, Frank- 

 land, Kekule, Odling, Berthelot, Buff, and Wurtz. I shall 

 begin this lecture by showing how the types can be explained 

 by means of these views. 1 



At the period in question Kolbe had attacked Gerhardt's 

 mode of regarding substances as an arbitrary one/ 2 Wurtz 

 endeavours to show that this is not so, and that Gerhardt's four 

 types, which, in his opinion, can be reduced to three, represent 

 different states of condensation of matter. Besides the hydro- 

 gen type H 2 , Wurtz also assumes the types H 2 H 2 and H 3 H 3 . 

 Water, H 2 O, formed by the replacement of H 2 by O, corre- 

 sponds to the former, while ammonia represents triple condensed 

 hydrogen, in which one half of this element is replaced by 

 trivalent nitrogen. Since all of these formulae correspond to 

 the same volume of the substances in the gaseous state, the 

 view of Wurtz is fully justified. One atom of hydrogen corre- 

 sponds to one volume, to one half of a volume, or to one third 

 of a volume according to whether it is present in compounds 

 which belong to the type H 2 , H 4 , or H (i . Wurtz looks upon 

 the existence of still more highly condensed states of matter 



1 Ann. Chim. [3] 44, 306. 2 Lehrbuch der Chemie. I, 50. 



