THE ATOMIC VIEW OF NATURE. 



411 



Type 



20. 



Whilst the "Eadicle" theory of Berzelius and Liebig 

 sought to simplify the study of chemical compounds by 

 reducing them to a definite number of complex atoms, the 

 "Type" theory of Laurent and Gerhardt sought to attain 

 the same object by establishing a small number of simple theory. 

 formulae, corresponding to well-known simple substances, 

 under which the vast number of organic compounds could 

 be grouped. 1 The conception of a "type" exhibiting 



1 The type theory was slowly and 

 hesitatingly developed. Dumas, 

 whose researches about 1835 pre- 

 pared the way, did not himself 

 draw the immediate consequences ; 

 this was done by Laurent, "who 

 maintained that the structure and 

 chemical character of organic com- 

 pounds are not materially altered 

 by the entrance of chlorine and the 

 separation of hydrogen" (E. v. 

 Meyer, 'History of Chemistry,' p. 

 261). Laurent then elaborated his 

 theory of " Nuclei. " They remind 

 one of Berzelius's and Liebig's radi- 

 cles. The nuclei were the ground- 

 work of organic compounds ; they 

 were not unalterable as the radicles 

 had been considered to be. Dumas, 

 who at first repudiated Laurent's 

 ideas, was later on, through his 

 own experimental discoveries, led to 

 adopt similar views. The " radicle," 

 as the permanent constituent in or- 

 ganic compounds corresponding to 

 the elements in inorganic chemistry 

 had given way to the changeable 

 nucleus, which only preserved its 

 form ; the unchangeable principle 

 was found in the form, the structure 

 or type, instead of in the substance 

 of the simple or composite consti- 

 tuents. This led to an extensive 

 study of the forms of chemical 

 compounds as expressed by their 

 formulae, and apart from the study 

 of the properties of the original 

 constituents. Types were invented, 



frequently in a somewhat arbitrary 

 manner. " The ultimate result was 

 that an empty scheme of formula- 

 tion carried the day over what was 

 really good in this doctrine" (ibid., 

 p. 264). "The unitary conception 

 was to step into the place of the 

 dualistic. . . . Every chemical com- 

 pound forms a complete whole, and 

 cannot therefore consist of two 

 parts. The chemical character is 

 dependent primarily upon the ar- 

 rangement and number of the 

 atoms, and in a lesser degree upon 

 their chemical nature " (p. 265). 

 This is the beginning of the second 

 great step which was taken in the 

 elaboration of the atomic view of 

 matter and nature. The atomic view 

 first became a scientific instrument, 

 when arithmetical relations of a 

 definite and unalterable kind were 

 suggested and proved to exist ; it 

 became a yet more useful instru- 

 ment, when to the arithmetical 

 there were added geometrical con- 

 ceptions. Position, arrangement, 

 and structure are conceptions 

 which involve ideas of distance and 

 space. It is true that for a long 

 time these terms were used merely 

 symbolically ; the ultimate conse- 

 quences of such conceptions can 

 however not be avoided. The his- 

 tory of chemical theory in the 

 second half of the nineteenth cen- 

 tury is a proof of this. 



