18 BULLETIN - 1475, U. S. DEPARTMENT OF AGRICULTURE 
in size, in the color of its stems, and in the size and color markings 
of its seed. The oil content of the seeds ranges from 35 to 55 per cent, 
the average being about 45 per cent. 
The seed and oil of commerce come chiefly from India, China, the 
West Indies, and South America. India produces by far the 
largest quantity. During the nineteenth century large quantities of 
castor beans were produced in the United States, chiefly in Okla- 
homa, Kansas, Missouri, and Illinois. In 1900, however, production 
fell off until 1918, when, in response to the demand for aircraft 
lubricants, a crop estimated at 5,750 tons was produced in the South- 
ern States. 
Preparation 
The castor beans, freed from trash and stones, are decorticated in 
machines made for this purpose and are cold pressed, usually in hy- 
draulic presses. The No. 1 oil is pressed from sound seeds only. The 
resulting press cake is ground, heated with steam, and pressed hot 
to give the No. 3 oil. A bushel of castor beans (46 pounds) yields 
about 15 pounds of No. 1 and about 4 pounds of No. 3 castor oil. In 
some mills, after either the first or second pressing, the residual oil 
in the press cake is extracted with a volatile solvent, such as benzine 
or gasoline. 
Expellers, sometimes used to express the castor oil, press at the 
rate of 17 or 18 bushels of castor beans per hour. Expellers used for 
this purpose should have three worm flights on the pressing screw 
or shaft. The expeller with two worm flights has been found unsatis- 
factory. 
Before the No. 1 oil is placed on the market it is customary to heat 
it in a vacuum to remove the moisture and then agitate it with 2 to 4 
per cent of fuller's earth, along with 0.2 to 1 per cent of a bleaching 
carbon. The treatment of the oil is finished when the bleaching 
agents are removed by filtration. No bleaching has been found ef- 
fective for the No. 3 oil. This is attributed in part to the fact that 
with the present practice the color is fixed by overheating. Highly 
colored castor oil can be refined and bleached only when it has re- 
ceived the same care as is given to the preparation of other vege- 
table oils to be bleached. 
Grades 
The trade determines the quality of the oil by its color, clearness, 
and acidity. No. 1, a cold-pressed oil, is low in acidity, brilliantly 
clear, and nearly colorless. No. 3 varies in color from brownish yel- 
low to dark brown or dark green. The trade does not recognize any 
grade as No. 2. 
Uses 
The No. 1 oil is used for medicinal purposes and the No. 3 for 
technical purposes. The oil which has been extracted with a volatile 
solvent is sold for technical purposes after the removal of the sol- 
vent. As the press cake or extracted castor-oil meal is poisonous, it 
is used only as a fertilizer. 
A large quantity of castor oil is converted into the sulphonated 
castor oil of commerce, known for many years as Turkey red oil 
because of its use in dyeing cotton fabrics with alizarine. The pro- 
