8 BULLETIN" 769, U. S. DEPARTMENT OE AGRICULTURE. 
annual importation increased about 2,000,000 pounds. "While our 
importation of animal fats has not increased greatly during the last 
six years, the amount of some of the vegetable oils being imported 
has shown a remarkable increase. For instance, the importation of 
soy bean oil in 1917 was over ten times as great as in 1912, and now 
exceeds 265,000,000 pounds, more than twice as much as our cotton- 
seed oil exports. Similarly, in spite of the enormous increase in 
domestic production, the importation of peanut oil rose from 
7,626.000 pounds, in 1912, to 27,405,000, in 1917. 
TERMINOLOGY AND TECHNOLOGY OF THE OIL TRADE. 
Before discussing the raw materials from which our fats and oils 
are derived and the methods used in extracting and refining them, 
it may be weU to define a few of the terms peculiar to the oil industry. 
In the first place, there is, strictly speaking, no distinct difference 
between a fat and an oil. Both are mixtures of various fatty acids 
combined with glycerin to form what the chemist calls glycerids. 
Those combinations of glycerids which happen to be liquid at ordi- 
nary temperatures we term "oils," while those which are solid are 
popularly known as "fats." Although most of the so-called oils are 
obtained from the fruit or seeds of plants, as, for example, olive, pea- 
nut, and cottonseed oil, not all the vegetable glycerids are oils. Some 
are solid fats, or "butters," as cacao butter, the fat contained in 
chocolate, nutmeg butter, obtained from the nutmeg, and palm kernel 
and coconut oils, which, although liquid in the tropical countries 
whence they come, are fairly solid in the temperate zones. On the 
other hand, animals, as a rule, produce fats Yvhich are hard at ordi- 
nary temperatures, for example, lard and suet. There are, however, 
a few exceptions to this generalization, for lard oil, bone oil, and the 
fish and whale oils are not solid. 
Nearly all iats and oils contain some glycerids which solidify more 
readily than the rest of the product. These are called stearin, while 
the more liquid portion is known as olein. WTien a fat cools slowly, 
the stearin part of it separates as a fine, whitish precipitate, and settles 
out. This phenomenon may be observed when a kettle of lard which 
has been used for deep frying is allowed to stand in a warm place for 
several days. The fat does not regain its original smooth consist- 
ency, but separates into a solid (stearin) and a liquid (olein) layer. 
In the same way, many oils if chilled become cloudy, and show the 
presence of a sediment in the bottom of the receptacles containing 
them. As many housewives consider this sediment to be an impurity, 
it is customary in this country to cool salad oils until part of the 
stearin crystallizes out, and then filter them before they are placed 
on the market. This is called wintering the oil. To secure a fat 
