146 ON COD-LIVER OIL. 
a nitrate of iron (whose proportions of oxide was known) 
and ammonia, and the sulphuric acid by means of nitrate 
of baryta. 
In order to determine the presence and quantity of free 
phosphorus or sulphur, a given quantity of oil was decom- 
posed by concentrated nitric acid, and the quantity of phos- 
phoric and sulphuric acids in the oxidized liquid ascertained 
by the above mentioned method. More phosphoric acid 
was procured from the oxidized than from the unoxidized 
liquid, and the proportion of phosphorus was calculated from 
the excess of acid. 
7. Jlcttic and butyric acids. — De Jongh separated these 
volatile acids from cod-liver oil by adding sulphuric acid to 
the soda-soap, and distilling the liquid thus* obtained. The 
distilled product had a peculiar odour. It was saturated 
with barytic water, and evaporated to dryness. One por- 
tion of the residue was insoluble in alcohol, the other was 
soluble. The insoluble salt was acetate of baryta with two 
equivalents of water(=0 H 5 O 5 Ba 0;) the soluble salt was 
butyrate of baryta. The soluble salt obtained from the pale 
oil gave the formula 2 (C s H 6 O 3 ) Ba 0, 6 HO; that pro- 
cured from the pale brown sort gave the formula C 8 H 6 3 , 
BaO, 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 re- 
solvable into acetic and butyric acids — a supposition some- 
what improbable, seeing that phocenic acid contains con- 
siderably 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 
remarkable, because it leads to the supposition that it is con- 
tained in the form of a peculiar fat, which would be the 
acetate of lipule. 
