408 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



account for the fact that hydrogen was sometimes removed 

 (wholly or in part) without replacement. Thus, in the con- 

 version of alcohol into chloral by the action of bleaching 

 powder it was seen that "the ten volumes of hydrogen, 

 removed from the alcohol, have been replaced by only six 

 volumes of chlorine," or, in terms of modern formulae, five 

 atoms of hydrogen have been replaced by only three atoms 

 of chlorine. 



C 2 H 6 + 4 C1 2 = C 2 HC1 3 + 5HC1. 



Dumas explained this on the view that alcohol was com- 

 posed of ethylene and water; the ethylene obeyed the 

 ordinary law of substitution, whilst the water (as Berthollet 

 had observed in 1785) gave oxygen and hydrogen chloride, 

 thus : 



24 2 = C 2 HC1 3 + 3 HC1 

 H 2 O +C1 2 = O +2HC1 



= C 2 HC1 3 + 5HC1 



This removal of hydrogen without replacement was regarded 

 as a test for the presence of water, as distinct from other 

 forms of hydrogen, in the molecule. Thus, oxalic acid, 

 which loses hydrogen on oxidation to carbonic acid, 



H 2 C 2 4 - H 2= 2 0) 2 , 



was regarded as containing the whole of its hydrogen in the 

 form of water, and was written as a hydrate, CgO^HgO. 1 

 Berzelius (1838-1843) objects to the presence of 

 oxygen and chlorine in organic radicals and to the whole 

 theory of the substitution of oxygen and chlorine for 

 hydrogen, Berzelius, who had welcomed Wohler and 

 Liebig's discovery of the benzoyl radical as the dawn of a 

 new day in organic chemistry, soon repented of his rashness 

 in admitting oxygen as a constituent of an electro-positive 

 organic radical. In the particular case of oil of bitter 



1 C 4 O 3 ,H 2 O in the original (C-6). 



