30 BULLETIN 1475, tT. S. DEPARTMENT OF AGRICULTURE 
FISH OILS 
Menhaden oil is obtained from menhaden caught off the Atlantic 
coast of the United States from about May until November. The 
fish are delivered by automatic conveyors in a comparatively fresh 
condition from the steamers to the plant, where they are weighed, 
transferred to tanks, and cooked with steam. After cooking the fish 
scrap is allowed to settle and the oil to rise. The oil is separated 
from the water and clarified. The scrap is removed from the settling 
tank, pressed to further extract the oil, and dried. This oil is of a 
lower grade than that first obtained and is kept by itself. Oil from 
fresh fish is light colored. The longer the fish are kept before 
extracting the oil the darker the oil will be. The better grades of 
oil are wintered (p. 7) to separate the stearin, and some is bleached 
with fuller's earth to produce what is known in the trade as bleached 
winter white oil. Menhaden oil is used for currying leather, in the 
preparation of chamois skins, for tempering steel, for making soap, 
and for manufacturing paints, printing inks, and insecticide emul- 
sions. Sulphonated menhaden and other fish oils are employed 
chiefly by the textile and leather industries. The dried scrap is sold 
as a feed or as a fertilizer. 
Salmon oil, a by-product from the north Pacific canning industry, 
is exported in large quantities from British Columbia to England. 
The entire fish contains about 20 per cent of oil. The oil is obtained 
from the parts of the fish not suitable for canning. Like other fish 
oils, it is used principally by the soap and leather industries. 
Herring oil, made in Great Britain, Japan, and Norway, has poor 
drying properties. It is used largely by the leather industry. 
FISH-LIVER OILS 
For centuries cod-liver oil has been prepared from cod livers on 
the coasts of Japan and the Scandinavian Peninsula. A great deal 
is now made in Newfoundland. 
By the old method the livers, collected in barrels or vats, were 
allowed to rot while they were exposed to the air until the oil floated 
to the top. It could then be removed. Another process, which was 
used later, consisted in trying out the oil in pans over open fires. 
The oil made by either process was very unpalatable. About 1850 
the steaming method had come into use in Newfoundland and Nor- 
way. The oil first separated from fresh livers by modern equipment 
in clean establishments is of fine quality, both in color and flavor. 
This oil varies from a very light to a golden-yellow color. 
The electrolytic process recently developed for extracting cod-liver 
and other oils consists in passing the minced fresh livers, suspended 
in brine heated to about 155° F., through a series of cells, composed 
of pipes containing carbon rods. The electric current, passing be- 
tween the carbon electrodes and the pipes, through the brine solution 
Containing the livers, breaks the oil cells and liberates the oil. The 
oil is separated from the brine and solids by centrifuges. Three 
minutes after the livers have entered the cells the oil is obtained from 
the separators. 
For the production of medicinal cod-liver oil, the crude oil is 
clarified by filtration and sometimes bleached. It is then put through 
a wintering process (p. 7) to separate the stearin. 
