LECTURE X. 



INFLUENCE OF THE SCHOOL OF GMELIN THEORY OF RESIDUES 

 COUPLED COMPOUNDS GERHARDT'S DETERMINATION OF EQUIVA- 

 LENTS DISTINCTION OF ATOM, MOLECULE, AND EQUIVALENT 

 BY LAURENT NEW CHARACTERISTICS OF POLYBASIC ACIDS 

 MOLECULES OF THE ELEMENTS. 



THE battle was over, and the victory won. It had been shown 

 that, starting from the decompositions which substances undergo 

 under the influence of the \fllyanic current, we are not in a 

 position to explain the manifoTd reactions of organic chemistry, 

 and in particular, the phenomena of substitution. The founda- 

 tions had been shaken by the fact that positive hydrogen was 

 replaceable by negative chlorine, and the whole edifice the 

 electro-chemical theory collapsed. Organic chemistry had 

 shown that laws which had been advanced without reference 

 to the facts that it presented, did not harmonise with the teach- 

 ings of these facts. It was now a question, however, as to 

 whether organic chemistry could also render any positive ser- 

 vice whether it would be possible, starting from the facts 

 which it had already furnished, or which it would furnish in 

 the future, to establish new principles that might serve as the 

 basis of a chemical system. 



The way of looking at substances from the electro-chemical 

 point of view, and dualism also, were maintained in the case of 

 inorganic compounds. In order to do this, a sharp distinction 

 between the latter and organic compounds became necessary, 

 so that it might be possible to apply a doctrine to inorganic 

 compounds which had proved inapplicable to organic com- 

 pounds. If this doctrine was to be completely supplanted, 

 however, and if organic chemistry was to enjoy the fruits of its 

 victory, it was necessary that this younger branch of the science 



