90 PHILIPPINE RESINS, GUMS, AND OILS 
€ 
are changed considerably. This is especially true of the iodine 
value, which is decreased greatly, and of the specific gravity, 
which is increased. 
The question of the edibility of hydrogenated oils has been 
discussed to some extent in chemical literature.* 
It seems to be generally accepted by those who have investigated the 
matter carefully that the hydrogenated oils have as desirable a degree 
of edibility as the oils from which they are derived. It is even claimed 
that by destroying traces of certain unsaturated bodies thought to be slightly 
toxic in nature, hydrogenation renders the oil better adapted for human 
consumption. 
Concerning the hydrogenation of oils, Thompson 7 states: 
The combined capacity of the hydrogenating plants of Europe is esti- 
mated for 1914 at 250,000 tons (1,375,000 barrels), which is two or three 
times as much as has ever been treated. These plants are in England, 
Norway, Germany, and France, and are engaged at present chiefly on 
fats for soap and candles. They are hardening linseed, whale, soya-bean, 
and cottonseed oils. 
The great increase in the demand for margarin in Europe, for com- 
pound lard in the United States, and for hard soap all over the civilized 
world has resulted in closely crowding the supply of natural hard fats, 
while liquid oils are relatively abundant. A few years ago strictly edible 
liquid oils seemed to be growing scarcer, but the new scheme of deodoriza- 
tion began to relieve this shortage by lifting the so-called soap oils into 
the edible class. The same process was applied to copra and palm-kernel 
oils, and finally caused a scarcity of soap greases. Hydrogenation now 
promises a further readjustment of conditions by permitting the transfer 
at will of any oil from the liquid to the solid class, and it will bring into 
use some relatively rare oils, and encourage the production of still others. 
In producing oils intended for edible purposes, it is obvious 
that the highest grade of purity is desirable, to obtain which, 
the raw materials, such as seeds or fruits, should be selected 
carefully, and worked up rapidly, in as fresh a condition as : 
possible. Special care should be observed to avoid the presence 
of considerable quantities of free fatty acids, since these sub- 
stances tend to decompose the oils and cause rancidity. 
Seed oils which contain toxic substances are naturally unsuited 
for edible purposes. Such oils frequently have properties which 
make them especially valuable for various other purposes, such 
as the manufacture of medicinal preparations, paints, varnishes, 
etc. Certain seed oils, for instance, have unusual drying prop-. 
erties which make them useful as paint oils. Linseed oil, which 


* Ellis, C. The hydrogenation of oils (1919), page 323. 
+ Thompson, E. W. Cottonseed products and their competitors in 
northern Europe. Department of Commerce, Special Agents Series No. 
89. Part II, Edible oils, 1914, page 26. 
