2 BULLETIN" 781, U. S. DEPARTMENT OF AGRICULTURE. 
butter: kid, hard-palate, and horse fats; oleo oil and oleo stearin; 
ox-marrow, ox-tail, and turtle fats. Other papers have reported the 
digestibility of a large number of vegetable fats, 1 including olive, 
cottonseed, peanut, coconut, and sesame oils; cocoa butter; and al- 
mond, black-walnut, Brazil-nut, butternut, English-walnut, hickory- 
nut, pecan, corn, soy-bean, sunflower-seed, Japanese mustard-seed, 
rapeseed, and charlock-seed oils. The oils of such nuts as almond, 
black and English walnuts, Brazil nuts, and pecan are ordinarily 
consumed as constituents of the nuts in which they naturally occur, 
but with these exceptions practically all of the oils studied are com- 
monly separated from the materials in which they naturally occur 
before being used for table or culinary purposes. 
POSSIBLE RECOVERY AND USE OF BY-PRODUCT OILS. 
As a result of the enormously increased demand for fats and oils 
for both technical and edible purposes it has seemed desirable to 
make a study of the nature and value of fixed oils present in seeds 
and nuts not hitherto grown or utilized for the production of oil. 
For some time studies have been carried on by the Department of 
Agriculture to ascertain the commercial possibilities of recovering 
the fixed oils contained in many of the pits and seeds occurring as by- 
products of the fruit canning and drying industries. In 1908 Rabak 2 
reported studies on the chemical and physical characteristics and the 
commercial uses and value of the fixed and volatile oils which may be 
obtained from the peach, apricot, and prune kernels. He estimates 
that from 210 to 420 tons of peach-kernel oil (fixed oil) and from 350 
to 400 tons of apricot oil may be obtained from the by-product peach 
and apricot kernels produced in California alone. He also estimates 
that the amount of raisin-seed oil capable of being manufactured 
from waste raisin seed would be from 348 to 464 tons yearly. 3 He 
states 4 that the possible commercial utilization of the waste cherry 
pits of a normal year's output should yield 134 tons of fixed oil. In 
a recent paper the same author 5 states that the quantity of oil capa- 
ble of being extracted from tomato seeds occurring as a by-product of 
tomatoes used for pulping purposes (catsups, etc.) would be about 
343 tons annually. 
From these findings it is apparent that the quantity of oil obtain- 
able from the pits and seeds occurring as by-products is not small. 
In order to make the recovery of these oils a practical proposition 
even in those localities where the pits and seeds are to be had in suffi- 
l XJ. S. Dept. Agr. Buls. 505 (1917), 630 (1918), 687 (1918). 
2 U. S. Dept. Agr. Bur. Plant Indus. Bui. 133 (1908), pp. 34. 
3 U. S. Dept. Agr. Bur. Plant Indus. Bui. 276 (1913), p. 30. 
*TJ. S. Dept. Agr. Bui. 350 (1916), p. 16. 
e U. S. Dept. Agr. Bui. 632 (1917), p. 9. 
