514 FIXED OILS, FATS AND WAXES 



also of inferior quality but suitable for many technical purposes, 

 is obtained by keeping the livers until they are partially decomposed, 

 skimming off the oil that has separated and heating and pressing the 

 residue ; such oil is usually of a brownish colour. 



After the livers have been removed and the offal separated the 

 fish are dried, and form an important article of commerce. The 

 chief seats of the cod fishery are the shallow banks off Newfoundland, 

 and the Loffoden Islands near the north-west coast of Norway. 



Description. Cod-liver oil should be of a pale yellow colour, and 

 have a slight, fishy, but not rancid odour. Its specific gravity should 

 vary from 0*920 to 0*930 ; it is readily soluble in ether and chloro- 

 form, but sparingly in alcohol. 



Constituents. Cod-liver oil consists chiefly of jecolein and therapin 

 associated with palmitin and probably other fat-acids combined with 

 glyceryl. Traces of biliary acids, alkaloids (morrhuine, aselline), 

 cholesterol, iodine, &c., are also present. 



Jecolein and therapin consist of jecoleic and therapic acids combined 

 with glyceryl. Jecoleic acid is a very unstable acid belonging to the 

 oleic acid series. 



. Cod-liver oil is employed as a nutritive and is a food rather 

 than a drug. 



Adulterants. Cod-liver oil is liable to adulteration with other 

 fish-liver oils and with seal oil, the detection of which is exceedingly 

 difficult. The following characters have been suggested for a pure 

 cod-liver oil for medicinal use : 



Colour ..... Pale yellow 



Odour Slightly fishy, not rancid 



Taste Bland, not rancid 



Specific gravity . . . 0*925 to 0*931 



Saponification value . . . 179 to 198 



Free fat-acid calculated as oleic Not over 1*5 per cent. 



Melting-point of fat-acids . . 23 to 26 



Iodine value . . . 154 to 170 



Refractive index (20) . . Not under 1*4790 



If three drops of nitric acid (sp. gr. 1*4) are added to 15 drops of 

 cod-liver oil and the mixture vigorously stirred, it should develop a 

 bright, rose-red colour. 



Note. Whale oil (Balcena sp.), seal oil (Phoca sp.), dolphin oil (Delphinus 

 sp.), and shark oil (Carcharias sp.) are used as illuminants, lubricants, 

 for leather dressing and soap making. Large quantities of whale oil are con- 

 verted by hydrogenation into bland edible fats of varying degrees ol hardness. 

 (Compare Allen's ' Commercial Organic Analysis,' Vol. II.) 



