242 HISTORY OF CHEMISTRY. [LECTURE XII. 



mode of representing them, but it is a real fact that an atom of 

 water contains two atoms of hydrogen, and only one of oxygen ; 

 also that the quantity of chlorine equivalent to one indivisible 

 atom of oxygen is divisible by two, whereas the sulphur, like 

 oxygen, is dibasic, so that one atom is equivalent to two atoms 

 of chlorine. 59 



The investigations by Frankland, of the radicals containing 

 metals, and his views as to saturating capacity (compare p. 231) 

 had an important influence upon the development of the theory 

 of polyatomic radicals, as also had the interesting paper on 

 salts by Odling, and the important researches of Berthelot on 

 glycerine and of Wurtz on glycols. We shall consider these 

 more minutely. 



Odling 60 makes a distinct advance by applying the idea of 

 polybasicity to the metals also, and by reintroducing molecular 

 formulae for all salts, even for those of the sesqui oxides, for 

 which Gerhardt had written equivalent formulae. He not only 

 refers the polyatomic acids to condensed types, as Williamson 

 had done before him, but he is also acquainted with poly- 

 atomic bases, which can be regarded in a similar way. Thus, 

 for example, he writes ? 



Oxide of Bismuth QsO ; Nitrate of Bismuth 



Those metals which possess, according to Gerhardt, various 

 equivalent weights, now have several atomicities assigned to 

 them. Odling knows, for example, monatomic and triatomic 

 iron, and monatomic and diatomic tin, whence he obtains the 

 following formulae : 



to citric acid C *" 



Ferrous Fe' ) 

 oxide Fe'J 



59 Annalen. 90, 314. Gt> Journ. Chem. Soc. 7, I. 61 Odling indi- 

 cates the atomicity of the elements by means of the dashes to the right of 

 their symbols. 



