XVI.
SOME CHEMICAL PROBLEMS OF THE FLORIDA TUNGOIL INDUSTRY W. H. BEIsLEn, UN~~BRSITT OB FLORIDA, GAINE~VILLZ, FLORIDA
The importance of producing tung oil in the U. S. is evident when it is realized that our paint and varnish industry uses about 100,000,000 pounds of the oil annually, all of which is imported from China. Furthermore, the Chinese oil is not of the highest quality and purity, and the supply is sometimes interrupted by the civil disturbances that have been rather common in that country for the past several years. Tung-oil trees have been grown to a very limited extent in Florida for a generation or more. Large-scale planting of the trees began in 1923, when 14,000 trees were set out. Expansion of the industry bas been steady and rapid, which can be seen from the fact that in 1929 tung-oil groves covered 5500 acres and contained 560,000 trees. One of the f i s t problems in any industry is that of economical production of a high-quality commodity. The first consideration in the case of tung oil is to raise healthy, prolific trees that will produce a large yield of fruit with a high oil content. This is an agricultural problem in which the chemist must take part on account of the necessity of establishing the relationship of soil and fertilizer composition with tree growth and fruit and oil production. The next problem is to remove the oil from the fruit as cheaply and completely as possible. According to Mr. B. F. Williamson of Gainesville, Florida, this problem has already been studied to a considerable extent, using equipment and methods that are common to other vegetable oils. Hydraulic pressing has been found unsatisfactory because the cake retains about 15% oil and the oil seals the cloths rather rapidly. Extraction with volatile solvents was abandoned when it was found that the oil assumed the consistency of lard, due, apparently, to the extraction of foreign substances with the oil. The method now in use a t the only tungoil extraction plant in this country (located a t Gainesville, Florida) is by use of the Anderson Expeller. This is a continuous process which crushes the previously dried and hulled nuts, producing a light-colored, practically neutral oil. The cake from the Anderson Expeller carries about 5 per cent oil. It is valued at $35 to $40 per ton as a fertilizer on account of the 6 to 6.5 per cent ammonia and the potash ana phosphorus it contains. Recently the cake bas been found to be of greater value as a source of carbon for case-hardening steel. 2344
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I t is quite possible that further improvements might be made in the extraction of tung oil from the fruit and that additional uses for the press cake and hulls might be found which would further increase their value. Tung oil is an unusual oil because of its high refractive index and its polymerization at high temperature, I t would seem well worthwhile to make a careful physical and chemical study of this oil and its fatty acids (1). Additional knowledge of the physical and chemical properties of the fatty acids should be of considerable value in understanding the behavior of the oil. Tung oil is used for a large variety of purposes in China, and its uses in this country are multiplying rapidly. It is the opinion of the writer that the introduction of American tung oil on the market will encourage research that will open up new uses for the oil, both raw and heat-treated, that are not dreamed of a t the present time. The polymerization of tung oil, when heated well over 280°C., is a very interesting phenomenon. The polymerized oil is a dry, gummy mass having about the consistency of art gum. It is practically insoluble in all of the common solvents, and no uses for it are known to the writer. Here is a real problem awaiting solution by scientific research. It is fairly well known that tung oil, taken internally, is a powerful cathartic. Some insist that the oil is poisonous, whiie others deny it. A biochemical search of the fruit and oil for the presence of substances having medicinal value should be of considerable interest and such a study might lead to important discoveries.
Reference (1) Scientific Section. American Paint and Varnish Association, Circular No. 358.
