150 
ON COD-LIVER OIL. 
verted into grape-sugar. No such substance has hitherto 
been detected in cod-liver oil, and, therefore, it may be said 
the necessary ingredient to produce this characteristic re-ac- 
tion of oil of vitriol on cholic acid is wanting. Strecker has 
recently supplied the wanting link. In his valuable paper on 
ox-bile, to which I have already referred, he observes that 
acetic acid may be substituted for sugar. To the liquid 
supposed to contain bile add a few drops of acetic acid, and 
then concentrated sulphuric acid, when a magnificent pur- 
ple-red colour is developed. If the quantity of bile be small, 
it may be necessary to use heat. Now, as cod-liver oil 
contains acetic acid, we have the requisite agent to enable 
the oil of vitriol to act on the cholic acid, and the develop- 
ment of the purple or violet-red colour is then readily ac- 
counted for. 
I have already noticed the red colour produced by the 
action of oil of vitriol on gaduin (supposed by Berzelius to 
be derived from the bile.) Here then is another source for 
the red colour caused by the action of sulphuric acid on 
cod-liver oil. 
It follows, therefore, from what has been now stated, that 
oil of vitriol is a test for liver oils. It does not distinguish 
one liver oil from another, for it re-acts equally with the oil 
of the liver of the ray and with oil of the liver of the com- 
mon cod. Neither does it distinguish good cod-liver oil 
from bad, for it produces its characteristic re-action both 
with common brown cod-oil, and with the finest and palest 
qualities. But it serves to distinguish oil procured from the 
liver, from oil obtained from other parts of the animal. 
Pharmaceutical Journal, Feb. 1849. 
