CONSTITUTION . 7 



3. Acids of the Linolenic series. 



General formula CnHan.eOa- 

 CigHgoOa Linolenic acid and its isomers. 



4. Acids of the Clupanodonic series. 



General formula CnHan-gOg. 

 C^gH-jgOa Clupanodonic acid. 



5. Acids of the Ricinoleic series. 



General formula CnHgn _ 203- 

 CjgHjjOj Ricinoleic acid and its isomers. 



The relationship between the five series of acids, which 

 differ from each other successively by two atoms of hydrogen, 

 as shown by the formulae, 



CnHgijOg, CnHgn _ 2^)2, Cnrljn _ 402> ^"-211 — 6^2' ^■iid CnH^n — f\^2' 



is similar to that subsisting between the three series of hydro- 

 carbons having the general formulae, 



^-Ti"^2n + 2) Curi2ni ^n"^2ii — ?• 



The hydrocarbons of the first or Paraffin series arc said to 

 be saturated, by which is meant that each of the four valencies 

 of their carbon atoms are fully satisfied, as shown by the follow- 

 ing graphic formulae : — 



H H H H H 



H— C— C— H H— C— C— C»-H 



Ethane C2HJ Propane CgHg 



When, however, the graphic formulae of the corresponding 

 members of the second or define series are written, it is found 

 that if the tetravalency of carbon is maintained, there are not 

 enough hydrogen atoms to satisfy all these valencies, and, in 

 order not to leave any unsatisfied, the remaining valencies 

 must be united to each other, thereby joining two carbon 

 atoms to each other by more than one bond : — 



H H H H H 



I I I 



u—o-c=c—u 



u 



H H H 



Ethylene CjH^ Propylene C^Ug 



