454 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



of different families of elements, e.g. the fluorine and nitro- 

 gen families, and the magnesium and oxygen families, thus : 



These differences were precisely similar to those observed 

 in homologous series of organic radicals, e.g. 



Ammonium 18 Methyl 15 



mmonum 1 ety 15 



Methylammonium 32 Ethyl 29 ] 



Ethylammonium 46 Propyl 43 



Propylammonium 60 etc. Butyl 57 etc. J 3 



Dumas concluded that 



" Since the radicals of mineral chemistry show amongst 

 themselves the same general relations as the radicals of 

 organic chemistry, there is certainly room to bring the two 

 chemistries more closely together than is the case at the 

 present day" (Ann. Chim. Phys., 1859, 55, 202). 



Newlands's "relations between equivalents" (1864), 



Dumas was much restricted by using the old equivalents in 

 place of the newer atomic weights which were adopted im- 

 mediately afterwards in consequence of the work of Deville 

 and of Cannizzaro (pp. 514 and 343). If he had doubled 

 the equivalents of the oxygen and magnesium families, he 

 would have recognised that his scheme of " common differ- 

 ences " could be applied generally to all the elements. Thus 

 the four families which he considered specially would have 

 come together as in columns IV, V, VI and VIII of Table A. 



1 The equivalents of the oxygen and magnesium families require to 

 be doubled in order to give the modern atomic weights. 



