-------------------------------------------------------------------- Acid. | Formula. | Found in -------------------------------------------------------------------- Linolenic | C_{17}H_{29}COOH | Linseed oil. -------------------------------------------------------------------- Isolinolenic | C_{17}H_{29}COOH | Linseed oil. -------------------------------------------------------------------- Jecoric | C_{17}H_{29}COOH | Cod-liver and marine animal oils. -------------------------------------------------------------------- These acids are similar in properties to those of Class III., but combine with six atoms of bromine or iodine, whereas the latter combine with only four atoms. V. _Ricinoleic Series:_-- ----------------------------------------------------------- | | | | | | Acid. | Formula. | Melting | Found in | | | | Point, | | | | | deg.C. | | |------------|----------------------|---------|-------------| | | | | | | Ricinoleic | C_{17}H_{22}(OH)COOH | 4-5 | Castor oil. | ----------------------------------------------------------- This acid combines with two atoms of bromine or iodine, and is converted by nitrous acid into the isomeric ricinelaidic acid, which melts at 52 deg.-53 deg. C. Pure ricinoleic acid, obtained from castor oil, is optically active, its rotation being [alpha]_{d} +6 deg. 25'. _Hydrolysis or Saponification of Oils and Fats._--The decomposition of a triglyceride, brought about by caustic alkalies in the formation of soap, though generally represented by the equation already given (pp. 6 and 7)-- C_{3}H_{5}(OR) + 3NaOH = C_{3}H_{5}(OH)_{3} + 3RONa, is not by any means such a simple reaction. In the first place, though in this equation no water appears, the presence of the latter is found to be indispensable for saponification to take place; in fact, the water must be regarded as actually decomposing the oil or fat, caustic soda or potash merely acting as a catalytic agent. Further, since in the glycerides there are three acid radicles to be separated from glycerol, their saponification can be supposed to take place in three successive stages, which are the converse of the formation of mono- and diglycerides in the synthesis of triglycerides from fatty acids and glycerine. Thus, the above equation may be regarded as a summary of the following three:--