Raiford L. Holmes

Preparation of petroselinic acid

Petroselinic acid of a grade which is suitable for most laboratory applications has been prepared by a single crystallization of the mixed fatty acids of parsley seed oil from 90% ethanol. A product of higher purity has been prepared from this acid by application of urea segregation techniques for the removal of saturated materials. No evidence of the presence of unsaturated fatty acids other than petroselinic acid was found in either of these samples when their ozonolysis products were examined chromatographically. On the basis of iodine values, assuming the absence of other unsaturated materials, the purities of the two preparations are 96.0 and 99.4%.

Titration of cyclopropene esters with hydrogen bromide

Esters of the naturally occurring cyclopropene acids have heretofore been determined by titration with hydrogen bromide in glacial acetic acid. However, highly purified cyclopropenes had an apparent purity of only 83–86% by this method. The catalyzed addition of acetic acid during the titration has been shown to occur. Substituting toluene for the acetic acid not only gives the correct cyclopropene content, but also sharpens the end point of the titration. The new titration is performed at 70–75 C and 1,3-diphenylguanidine, which is soluble in toluene, should be used as a primary standard. The indicator solution is 0.03% crystal violet in butyric acid. Mono- and diglycerides and oxidized fatty compounds must be removed before titration. Oxirane oxygen can be determined by the new procedure, probably with an accuracy greater than that possible with hydrogen bromide in glacial acetic acid.

The characteristics of domestic tung oils

ConclusionDomestic tung oil is a very uniform product as shown by the determination of the chemical and physical properties of 74 samples taken over three successive milling seasons.The refractive index, refractive dispersion, and heat test are correlated with the total eleostearic acid content, the correlation coefficients being 0.69, 0.73, and −0.62 respectively, which indicates that any one of these values can be taken as a rough measure of the elostearic acid content. The correlation of the eleostearic acid content with the Wijs and hydrogen iodine values was lower, 0.48 and 0.53, respectively. A correlation of −0.81 was found between refractive index and heat test.

Effect of shell content and storage on expelling of tung nuts

Summary and ConclusionsExpeller tests were made on ground tung nuts containing all of the shell (33%) at the time of hulling and after the nuts had been in storage for one and two months. Comparative tests were also made on material containing about 24% shell which had passed through the disc huller in regular mill operation. One test was made on hand-shelled kernels which were entirely free of shell.It was found that meal containing all of the shell not only processed satisfactorily, but the recovery of oil from such material was somewhat higher than from material containing about two-thirds of the shell. The amount of oil expelled per hour was about the same in both cases. The kernels completely cleaned of shell expelled very inefficiently. In general, therefore, it seems that, with the particular type of expeller used, a considerable amount of shell in the meal is essential for efficient expelling.Bags of nuts with hulls removed but with the shells intact showed no deterioration after two months’ storage in a well-ventilated shed.

Materials balance in a tung oil mill

SummaryWeights were determined and analyses made of tung fruit milled and of all products leaving the mill for two runs of about 90 tons each in a commercial mill under normal operating conditions. Dry matter, oil, and nitrogen in the fruit were satisfactorily accounted for in products leaving the mill, 101% of the oil being accounted for in each run. This showed that the methods of analysis and sampling were accurate.Losses occurred principally in particles of kernels occluded with the hulls and in the screw-press cake. Seventy-eight and 82% of the oil in the fruit was recovered as filtered oil.Repressing the filter-press cake by adding it back to the stream of ground nuts just before they entered the screw-presses was not proven to be economical as at the end of the run just as much cake was on hand, and it had as high an oil content as if no filter cake had been fed back through the screw presses. Only about half as much oil could be filtered per filtration cycle, resulting in an increase in cost of labor and a decrease in filtering capacity.The apparent oil content of the screw-press cake decreases by about 2% after four to eight days as compared to its apparent oil content at the time of pressing because of polymerization. Thus, screw-press cake samples should be analyzed for oil as soon as possible after extrusion.

The effect of extended storage on the properties of tung oil

SummaryTung oil has been stored in clean, well-filled gallon containers for more than three years and at the end of that time still met A.S.T.M. specifications.Storage locale (indoor, outdoor, sheltered, or unsheltered containers) and the exterior coating on the containers in exposed locations were found to be of less importance than protection of the stored oil from atmospheric oxygen.The most pronounced effect of prolonged storage on tung oil is a shortening of the heat test (gel time at 282°C.).Uncontaminated tung oil does not spontaneously isomerize during storage.

Loss of oil in hulling tung fruit in the field and at the mill

SummaryMethods for analyzing commercial tung hulls for oil have been developed. Samples of tung hulls from mill and field hulling operations have been collected and analyzed. The loss of oil when the fruit are hulled was found to vary from 0.6% to 7.3% with an average loss of 2.7% based on the total amount of oil in the fruit. The difference in the loss of oil between grove and mill hulling was not significant. With a loss of 2.7% of the oil in hulling, a recovery of 87.9% oil on the hulled nuts would be equivalent to a recovery of 85.5% oil on the whole fruit.

Studies on the refractive index and dispersion of American tung oil

Conclusions1.Tung oil has a refractive index and a dispersion so far above those of any other common oil that both are valuable criteria for identification purposes. With proper equipment the dispersion, in addition to the refractive index, can be determined with little extra effort and would confirm the conclusions drawn from the refractive index.2.Mixtures of tung oil with another vegetable oil (except oiticica and other rare conjugated oils) can be analyzed to within 0.5% from the refractive index for either the sodium or the mercury line if the refractive indices of the separate oils are known. The mixtures can be analyzed from the dispersion to within about 1% of the correct composition if the dispersions of the separate oils are known. If the adulterating oil is not known the adulteration can be more closely estimated from the depression of the dispersion than from the depression of the refractive index.3.When tung oil is bodied by heat the refractive indices for the sodium and mercury lines and the dispersion fall rapidly and continuously to the point of gelation, but the changes are so similar that no worth-while additional information is obtained by determining more than one refractive index. The fact that refractive index decreases as viscosity increases suggests the use of the refractive index in controlling the bodying of tung oil.4.Other things being equal, the refractive index for the mercury line should give more accurate information on tung oil than that for the sodium line because of the greater changes in the refractive index for the mercury line upon adulteration or heating.5.A correlation coefficient of 0.83 was found for refractive index with the diene number of tung oil. A lower correlation coefficient was found for refractive index with the iodine number, but the latter would probably be higher if a more accurate method for the determination of the iodine number of tung oil were available.

The Determination of Moisture in Tung Fruit

Summary and ConclusionsSix methods for determining moisture in tung fruit and seeds were compared.The highest moisture values, and probably those most reliable, were obtained by drying the ground tung fruit in the vaccuum oven at 101°C. for 2.5 hours under 12-mm. pressure, and by the Karl Fischer titration method. In using the Karl Fischer method on tung products, the sample must be digested in methanol at 60°C. Of these two methods the vacuum oven method is simpler and generally preferable.Somewhat lower moisture values were obtained by the forced draft oven and toluene-distillation methods. The results obtained in the forced draft oven method were low because of oxidation of the oil in the samples. One hour at 101°C. in the forced draft oven seems to be the optimum time for moisture determination, and no appreciable error in the oil content results from using the percentages of moisture so determined to calculate the oil content to basis of sample as received.For routine analysis, heating the ground tung fruit sample in a hot air blower for 15 minutes at 126.7°C. (260°F.) and adding a correction of 1.35% to the percentage of moisture obtained gives sufficiently accurate values for factory control purposes.The radio frequency meter gave values close to those obtained in the vaccum oven method against which it was standardized. It was necessary to standardize the meter separately for fruit, seeds, and kernels. In practice many samples of wet fruit would be encountered which would exceed the range of the particular instrument used.

The equilibrium moisture content of tung fruit and its components at different relative humidities

SummaryThe equilibrium moisture contents at 25°C. were determined for the whole tung fruit, the outer hull, the inner hull, shell, kernels, and seed of the fruit, and on the cake from continuous screw presses at nine different relative humidities. The relative humidities were maintained by enclosing saturated solutions of different salts in desiccators in a room maintained at constant temperature.