![Thumbnail: [Volume 56, 1926 page 647]](/journals/rsnz/images/rsnz_56/thumbnails/rsnz_56_00_0804_0647_ac_02.gif)
Methods.
Except in the case of the livers, the minced and weighed material was first extracted twice in succession with double its bulk of alcohol (approximately 90 per cent.) at room-temperature, and the residue was dried in the
![Thumbnail: [Volume 56, 1926 page 648]](/journals/rsnz/images/rsnz_56/thumbnails/rsnz_56_00_0805_0648_ac_02.gif)
sun, extracted with ether (Soxhlet), and the fat so obtained was weighed separately. The alcohol of the alcoholic extract was distilled off, and the residue, after drying, was also extracted with ether, and so we obtained the fat that was soluble in both alcohol and ether, as well as the fat soluble in ether only. In all the operations we avoided exposure of the fats to heat and oxidation as far as was practicable in our circumstances.
The fish-livers were so fatty that we found it best to extract some of the fat with ether by shaking up and drawing off the ethereal layer before attempting to dry completely. The usual extraction method then followed, and all ether-soluble material was combined and weighed.
The fatty acids and “unsaponifiable” material were obtained from 8 to 10 grammes of fat thoroughly saponified with alcoholic potash. After diluting the soaps and driving off the alcohol, ether was used in separating funnels to remove the “unsaponifiable” part. The fatty acids were then obtained by acidifying the residue.
The iodine values of the fatty acids and oils were estimated by Wijs's method, and the mean molecular weight by titration with one-fiftieth normal alkali.
The results are given in the table.
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| — | Whale-feed. | Red Cod (A) feeding on Whale-feed. | Red Cod (B) feeding in Deep Water. | ||
|---|---|---|---|---|---|
| Flesh. | Liver. | Flesh. | Liver. | ||
| Water percentage | 79.0 | 44.3 | 81.0 | 46.0 | |
| Solids by difference | 21.0 | 55.7 | 19.0 | 54.0 | |
| Fat percentage | 1.3 | 0.8 | 47.3 | 0.9 | 40.4 |
| Nature of the fat * | Brown pasty mass | Brown pasty mass | Dark-red oil | Pasty mass | Red oil. |
| Percentage of the fat soluble in alcohol and in ether | 80.0 | 77.0 | 68.0 | ||
| Percentage of “unsaponifiable” matter | 6.9 | 5 † | 10.8 | 5 ‡ | 9.6 |
| Nature of fatty acid—Solid at | 15° C. | 15° C. | 15° C. | 15° C. | 15° C. |
| Iodine value of the fatty acids (Wijs) | 138.8 | 139.2 | 113.1 | 135.5 | 111.3 |
| Iodine value of the liver-oils | 85.0 | 72.0 | |||
| Mean molecular weight of fatty acids | 309.0 | 334.0 | 282.0 | 335.8 | 283.0 |
[Footnote] * All these fats contained appreciable amounts of lecithin, as shown by the development of trimethylamine during the saponification. The liver-oils gave black resinous pitch-like acids denser than water.
[Footnote] † Approximate.
[Footnote] ‡ Approximate.