050 
COD-LIVER OIL. 
from the pale oil gave the formula 2 (C s H 6 O s ), Ba O, 6 HO ; 
that procured from the pale brown sort gave the formula C 8 H 0 0„ 
Ba O, HO. 
Rancid cod-liver oil emits an odour like common fish or train- 
oil, and we might, therefore, expect that phocenic acid would be a 
constituent of cod-liver oil. De Jongh did not detect it; but thinks 
that phocenic acid may perhaps be resolvable into acetic and butyric 
acids—a supposition somewhat improbable, seeing that phocenic 
acid contains considerably more carbon than either butyric or acetic 
acid. Berzelius observes, that the presence of acetic acid in cod- 
liver oil in a form which is not extractable by water is remark¬ 
able, because it leads to the supposition that it is contained in the 
form of a peculiar fat, which would be the acetate of lipule. 
It will be unnecessary to enter into any details with respect to 
the other constituents of the oil. 
The characters by which we judge of the genuineness, purity, 
and goodness of the oil are partly physical, partly chemical. 
The physical characters which are usually employed are, prin¬ 
cipally, colour, odour, and flavour. The finest oil is that which is 
most devoid of colour, odour, and flavour. The oil as contained in 
the cells of the fresh liver is nearly colourless, and the brownish 
colour possessed by the ordinary cod-oil used by curriers is due 
to colouring matters derived from the decomposing hepatic tissues 
and fluids, or from the action of air on the oil. Chemical analysis 
lends no support to the opinion, at one time entertained, that the 
brown oil was superior, as a therapeutical agent, to the pale oil. 
Chemistry has not discovered any substances in the brown oil 
which could confer on it superior activity as a medicine. On the 
other hand, the disgusting odour and flavour, and nauseating qua¬ 
lities of the brown oil, preclude its repeated use. Moreover, there 
is reason to suspect that, if patients could conquer their aversion 
to it, its free use, like that of other rancid and empyreumatic fats, 
would disturb the digestive functions, and be attended with inju¬ 
rious effects. 
Of the chemical characters w r hich have been used to determine 
the genuineness of cod-liver oil, some have reference to the iodine, 
others to the gaduin or to the bile constituents. I have already 
stated that some fraudulent persons are said to have admixed iodine 
(either free iodine or iodide of potassium) with train oil to imitate 
cod-liver oil. The presence of this substance may be readily detected 
by adding a solution of starch and a few drops of sulphuric acid, by 
which the blue iodide of starch is produced; or the suspected oil 
may be shaken with alcohol, which abstracts the iodine. 
But though we may thus readily prove that the suspected oil 
