92 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 t 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 pi-esent 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. 



t 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. 



