These are fatty acids which contain double bonds. Iodine values vary according to the degree of unsaturation. They are generally liquid at room temperature; the general formula is CnH2n-1 COOH. Unsaturated fatty acids are further divided according to the degree of unsaturation.

1. One double bond:Palmitoleic acid C16: 1; 9Oleic acid C18: 1; 9
2. Two double bonds:Linoleic acid C18: 2; 9; 12
3. Three double bonds:Linolenic acid C18: 3; 9; 12; 15
4. Four double bonds:Arachidonic acid C20: 4; 5; 8; 11; 14

Table 4.2 Unsaturated Fatty Acids