[56] ‘Elem. Mat. Med.,’ &c., 3rd edit., iii, 2339.
Among the tests of purity, that generally relied on is known as the ‘sulphuric acid test.’ See Oils (Fixed): Purity.
Dorse oil, and other FISH OIL, sold as ‘LIGHT-BROWN COD-LIVER OIL,’ exhibit with this test much lighter reactions, which closely resemble those of LIVER-TRAIN and WHALE-TRAIN OIL.
To detect the presence of combined iodine, upon which, by some, the therapeutic value of cod-liver oil is thought to depend, the sample is saponified by trituration with a little caustic potassa and hot water, the resulting soap cautiously incinerated, the ashes digested with water, and the whole thrown on a filter. The
usual tests for iodine may be then applied to the filtered liquid.
The presence of iodine artificially added is best detected by agitating the oil with a little rectified spirit, and then testing this last for iodine. Or, a little solution of starch and a few drops of sulphuric or nitric acid may be at once added to the oil, when a blue colour will be developed if iodine, or an iodide, has been mixed with the sample.
The sp. gr. of the pale oil is ·9230 to ·9238; of the light-brown oil, ·9240 to ·9245; of the dark-brown oil, ·9290 to ·9315. The density is, however, apt to vary a little with the quantity of moisture present.
Uses, &c. Cod-liver oil is a most valuable medicine in a great variety of diseases, more especially in glandular indurations and enlargements, scrofula, phthisis, rheumatism, gout, certain cutaneous diseases, amenorrhœa, chlorosis, caries, rickets, &c. To be of service, however, its use must be continued for several weeks, and the oil must be recent.—Dose, 1 to 2 table-spoonfuls, 3 or 4 times daily, or oftener.
Oil, Col′za. From the seeds of Brassica campestris, var. oleifera, or colza de printemps, a variety of Brassica campestris (Linn.). It may be regarded as a superior sort of rape oil. Burns well in lamps, especially after being refined. Sp. gr. ·9136. Prod. 39%. The term ‘colza oil’ is commonly applied to ordinary refined rape.
Oil, Cottonseed. Syn. Oleum gossipii seminum, L. From the seeds of Gossypium Barbadense. Drying.