LECTURE VIII.] HISTORY OF CHEMISTRY. 145 



other elements. But this is not the only kind of change that 

 the nucleus can undergo, and here Laurent differs from Dumas. 

 Thus an indefinite number of atoms may attach themselves to 

 the radical, and be removed from it again without being 

 replaced ; whereas, as already stated, an atom cannot be 

 removed from the nucleus without the entry of its equivalent, 

 since the destruction of the whole group would otherwise 

 ensue. Such destruction infallibly occurs as soon as carbon, 

 in the form of carbonic anhydride, carbonic oxide, etc., is 

 removed from the compound ; in which case either a complete 

 decomposition takes place, or a fresh nucleus is formed. The 

 relation of this nucleus to the first one is not further defined, 

 however. According to Laurent, the subsidiary nuclei show a 

 great resemblance to the fundamental radicals in their physical 

 and chemical characters ; the derived nuclei, obtained by 

 attachment of new atoms, have, on the other hand, acquired a 

 different character. Thus a union with hydrogen and oxygen 

 (water) usually brings about the formation of alcohol ; a neutral 

 oxide is formed by the taking up of two atoms of oxygen, a 

 monobasic acid by the taking up of four atoms, and a dibasic 

 acid by the taking up of six atoms of oxygen. 



Laurent further adopts a geometrical conception respecting 

 organic compounds. In accordance with this conception the 

 nuclei are prisms in whose angles the carbon atoms are located, 

 whilst the edges are formed by the hydrogen atoms. These 

 edges can be taken away and replaced by others, without the 

 figure undergoing any considerable changes. But should the 

 place be left unoccupied, the internal connection would come 

 to an end and the whole would fall to pieces. Atoms can still 

 be added to the prisms so as to form pyramids ; and the whole 

 figure may be surrounded in this way, by which means its form 

 is, of course, altered. These pyramids can be removed, where- 

 upon the original prism makes its appearance again. 



In our matter-of-fact science we are not accustomed to such 

 imaginative views, and so it may appear as if nothing of any 

 value for chemistry lies hidden behind them. In order to 

 disprove this, however, I shall translate the hypotheses of 



K 



