35 2 HISTORY OF CHEMISTRY. [LECTURE XVI. 



aromatic compounds, and, in particular, upon the hydro- 

 phthalic acids. 109 



While Baeyer's intention in these investigations was to 

 discover weaknesses in the theory, and even to modify it, his 

 labours led instead to a further confirmation of it. Besides 

 this, the credit is due to him of having advanced the so-called 

 tension theory, 110 which has already proved of service in some 

 cases. 



Emphasis must be laid upon the fact that the important 

 consequences which the theory of the asymmetric carbon atom 

 brought forth, gave a spur to the more and more complete 

 application of stereo-chemical considerations. In this con- 

 nection the numerous researches may be mentioned which 

 deal with the non-occurrence of certain reactions, and explain 

 this on stereo-chemical grounds. 111 Amongst these investi- 

 gations the best known are those of Victor Meyer on the 

 formation of esters. 112 The asymmetry of the nitrogen atom 

 may also be mentioned in this connection. 



The researches of Hantzsch and Werner 113 were of funda- 

 mental significance with respect to the last-named subject, and 

 they were capable of explaining the isomerism amongst oximes, 

 which was already familiar at that time. Hantzsch afterwards 

 extended the views respecting this matter, and turned them to 

 account in explaining the isomeric hydrazones 114 and diazo- 

 compounds. 115 It is true that it was only geometrical isomerism 



109 Annalen. 245, 103 ; 251, 257 ; 156, I ; 258, I and 145 ; 266, 169 ; 

 269, 145 ; 276, 255. no Berichte. 18, 2278. m Hofmann, Ibid. 17, 

 1915; and 18, 1825; Jacobson, Ibid. 22, 1219; 2$, 992; 26, 681 and 

 699; etc. ; Pinner, Ibid. 23, 2917; Kuster and Stallberg, Annaien. 278, 

 207. 113 Berichte. 27,^510, 1580, 3143; 28 Kef. 301 and 916; 29, 

 830 ; etc. 113 Ibid. 23, 1 1 ; Werner, Raumliche Anordnung der Atome 

 in stickstoffhaltigen Molekiilen, 1890. Compare further, the previously 

 published researches of Willgerodt, J. pr. Chem. 37, 449 ; Burch and 

 Marsh, Journ. Chem. Soc. 55, 656 ; and especially van 't Hoff, Ansichten 

 liber die organische Chemie, Braunschweig 1878-81. 114 Fehrlin, 



Berichte. 23, 1574 ; Krause, Ibid. 23, 3617 ; Hantzsch and Kraft, Ibid. 24, 

 3511 ; Marckwald, Ibid. 25, 3100. 115 Ibid. 27, 1702, 1726, 1857, 2099, 

 2968, 3527 ; 28, 741, "24, 1734; etc. 



