DECOMPOSITION OF ORGANIC COMPOUNDS. 251 



//. A molecule may split up into two or more molecules. 

 For instance : 



C 6 H 12 6 = 2C 2 H 6 + 2C0 2 . 



Grape-sugar. Alcohol. Carbon 



dioxide. 



c. Two molecules, either of the same kind, or of different 

 substances, may unite together directly : 



+ 2Br = C 2 H 4 Br 2 . 



Ethylene. Bromine. Ethylene 



bromide. 



d. Atoms may be removed from a compound without re- 

 placing them by other atoms : 



C 2 H 6 O + O == C 2 H 4 O + H 2 O. 



Alcohol. Oxygen. Aldehyde. Water. 



e. Atoms may be removed and replaced by others at the same 

 time (substitution): 



C 2 H 4 O 2 + 2C1 = C 2 H 3 C10 2 + HC1. 



Acetic acid. Chlorine. Monochlor- Hydrochloric 



acetic acid. acid. 



Action of heat upon organic substances. As a general rule, 

 organic bodies are distinguished by the facility with which they 

 decompose under the influence of heat or chemical agents ; the 

 more complex the body is, the more easily does it undergo de- 

 composition or transformation. 



Heat acts differently upon organic substances, some of which 

 may be volatilized without decomposition, whilst others are de- 

 composed by heat with generation of volatile products. This 

 process of heating non-volatile organic substances in such a 

 manner that the oxygen of the atmospheric air has no access, 

 and to such an extent that decomposition takes place, is called 

 dry or destructive distillation. 



The nature of the products formed during this process varies 

 not only with the nature of the substance heated, but also with 

 the temperature applied during the operation. The products 

 formed by destructive distillation are invariably less complex in 

 composition, that is, have a smaller number of atoms in the 

 molecule, than the substance which suffered decomposition ; in 



