THE PRINCIPLES OP ORGANIC CHEMISTRY 39 



We thus reach, a very important fundamental conception, 

 viz., that of the weight of a molecule of a substance in terms 

 of the weight of a molecule of hydrogen. 



The difference between molecules and atoms receives 

 confirmation from the properties of elements in what is called 

 the nascent state, i.e., at the moment of their release from 

 combination. 



Thus if gaseous hydrogen is passed, e.g., through a yellow 

 solution of ferric chloride, no change takes place ; if, however, 

 the hydrogen is evolved actually in the solution by inserting, 

 e.g., a strip of zinc, the ferric chloride is rapidly reduced with 

 formation of a colourless ferrous salt containing less chlorine 

 than the ferric chloride. The hydrogen in the nascent state 

 combines with the chlorine of the latter according to the 

 following equation : — 



FeClj + H = FeCls + HCl 



Tellow ferric Colourless 



ctiloricle ferrous chloride 



This is a typical instance of a process known generally as 

 reduction, when oxygen, or its equivalent, is removed from 

 a compound. 



The oxidising properties of such substances as ozone and 

 hydrogen peroxide are due to the liberation of oxygen from 

 them in the nascent state. Ozone is considered to be a 

 condensed form of oxygen containing three atoms in the 

 molecule ; on coming in contact with oxidisable matter the 

 third atom of oxygen is liberated and ordinary oxygen with 

 two atoms in the molecule is set free, thus : — 



O3 + metal =02 + metallic oxide 



Similarly hydrogen peroxide (H2O2) readily loses one atom 

 of oxygen with liberation of ordinary water, HjO. 



As a matter of fact ozone and hydrogen peroxide are 

 mutually destructive when they are brought together, for the 



