1 86 HISTORY OF CHEMISTRY. [LECTURE X. 



replace the amid- by the imid- group. 34 Gerhardt was able to 

 associate himself with this conception without involving himself 

 in any further consequences, since his formulae did not attempt 

 to express the arrangement of the atoms but were only contracted 

 equations. They were not intended to represent what the com- 

 pounds are, but merely what their nature is and what becomes 

 of them : 35 they were meant to indicate the modes of formation 

 and of decomposition of substances. Gerhardt was the first to 

 advance the view that we should not conclude from the decom- 

 position products as to the arrangement of the atoms, because 

 the latter are set in motion by the reaction. 36 According to 

 him, several formulae were therefore possible for the same sub- 

 stance, and different residues (radicals) might be assumed in it 

 according to the decompositions which it was desired to 

 emphasise. In this way the point of the controversy, which 

 had been carried on so fiercely and so long, as to the nature of 

 the radicals, was demolished. Afterwards, Gerhardt comes to 

 employ empirical formulae, which had been recommended by 

 Liebig on account of the constantly growing divergences of 

 opinion as to rational constitution. 37 Conjointly with Chancel, 

 he introduces, in 1851,- the synoptic formulae, 38 which never 

 met with any general acceptance because they were incon- 

 venient and not easily understood. If the form was new, still 

 the idea was simply the old one. This mode of writing formulae 

 was likewise intended only to represent the formation and de- 

 composition of substances, and it too consisted of contracted 

 equations. The great advantage of this way of regarding the 

 matter lay in the possibility of advancing several rational for- 

 mulae for one substance, whereby new analogies and differences 

 made their appearance and gave rise to a large number of 

 investigations. 39 



34 Comptes Rendus. I, 39. 35 Gerhardt, Introduction a 1'etude de 



la Chimie, 1848. x Compare Baudrimont, Comptes Rendus. 1845. 



37 Annalen. 31, 36. 38 J. pr. Chem. 53, 257. 39 It may be remarked 

 here, in passing, that Gerhardt, a few years later, again replaces imid, NH, 

 by amid, NH 2 , after Laurent (J. pr. Chem. 36, 13), in 1844, had adopted 

 and sought to establish Hofmann's conception of aniline as phenamid. 



