Iodine Number and Refractive Index of Perilla Oil C . A. LATHRAP,Curtis & Tompkins, Ltd., San Francisco, Calif.
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LTHOUGH perilla oil has only comparatively recently come into prominence, considerable and increasing quantities are now being imported into this country from the Orient. It is used chiefly in the paint and varnish and allied trades where its properties make it of particular value. The study of the constants of perilla oil as criteria of purity has not been carried as far as with some of the other oils, although its comparatively high price makes it a profitable field for adulteration. The more or less arbitrary standards now existing are perhaps somewhat open to argument.
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FIGURE1. REFRACTIVEINDEXA N D IODINE NUMBEROF PERILLAOIL Manchurian greenish gray sample Manchurian brown sample Manchurian pale brown mixed sample Korean No. 1 sample Korean No. 2 sample 6. Korean No. 3 sample 1. 2. 3. 4. 5.
The American Society for Testing Materials in its specification for raw or refined perilla oil (1) gives the iodine number (Hanus) minimum as 191.0 and does not mention the refractive index. Pickard (a), in a very interesting
review of the analytical results of perilla oil furnished by several laboratories, states in a summary concerning the iodine number, in substance as follows: A survey of all the figures before us warrants the conclusion that very little, if any, pure perilla oil will have a Hanus iodine number lower than 195. Assuming this to be correct, we find that our extremes are about ten points, that is, from 195 t o 205.
Referring to refractive index, he says: There are very few determinations which are below 1.480 at 25" C. The highest figure listed is 1.4819, while the lowest one is 1.4794. We are inclined t o believe, however, that no pure erilla oil would have a refractive index below 1.480 and, thereFore, would set that as the minimum figure at 25" C. So far as our results go, we have but one which is above 1.4815. Therefore, it would seem that, if this figure were set as a maximum, no pure perilla oil would be excluded thereby.
TESTSON ORIENTALPERILLA SEED An old importer of perilla oil on this coast, while recently traveling in the Orient, arranged to have some six grades of perilla seeds sent to this laboratory for experimentation. These seeds were hand-picked here, and all foreign seeds, chaff, dirt, or damaged seeds eliminated, the material pressed all being sound perilla seed of the grades designated. These were cold-pressed, though the modern practice is hot-pressing, which, however, should not appreciably affect the constants though it does the color. It is to be noted in Table I that there is quite a wide range between the minimum and maximum iodine numbers for these seeds of known purity (roughly 15 points). The accepted published minimum for the Hanus value would, on this basis, appear somewhat too high. Based on the limited number of seed samples represented in this experiment, it would not be possible to prophesy what limitations of index of refraction or iodine value should be placed on a pure perilla oil, but it is evident that present accepted standards do not fully cover the practical facts in the case. As the refractive index and iodine value, more then anything else, tend to portray the purity of perilla oil, the subject should be given more thorough consideration, based on a greater variety of seeds of known purity and extended over a number of seasons. Such an investigation should establish a more definite knowledge of actual limitations of pure perilla oil. I n the course of regular routine work, this laboratory has been called upon to pass on the purity of a large number of shipments of perilla oil arriving a t Pacific Coast ports. The shipments have arrived both in bulk and in drum lots, and
OIL FROM HAND-CLEANED SEEDS TABLE I. ANALYSISOF COLD-PRESSED (Clear settled oil used for analysis) MANCHURIAN MANCHURIAN GREENISH MANCHURIAS PALE BROWN BROWN MIXED GRAY 0.9355 0.9342 1.4820 1.4816 0.54 0.88 191.1 191.6 20s.6 204.7 200.4 198.4 6.3 8.2 nus".. . . . . . 5.5
..................... .....................
30.0 1.8 8 Average difference between Wijs and Hanus iodine numbers of the nix samples
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30.0 1.8 5.9.
KOREAN No. 1 0.9324 1.4800 1.53 191.8 192.0 185.7 6.3 40.0 2.0
KOREAN No. 2 0.9326 1.4801 1.01 191.1 194.5 190.1 4.4 40.0 2.1
KOREAN No. 3 0.9326 1.4802 0.76 191.1 194.5 189.6 4.9
40.0 2.1
July, 1932
ISDUSTRIAL AND ENGINEERING CHEMISTRY
a large majority of them have been passed as pure. A detailed tabulation of all these results would require too much space, and therefore only a condensed summary of the iodine number (Wijs) and refractive index on approximately one hundred samples, passed as pure during the past few seasons, is included: >I %XIMUM MINIMUM AVERAQE Iodine number (Wijs) Refractive index a t 25’ C.
207.0 1.4818
193.3 1.4802
200.4 1.4811
About 20 per cent of the oils included in the tabulation had indices higher than 1.4815, the limit suggested by Pickard, while none had indices below the lower limit. During the course of the tabulation, several interesting points were brought to light. The interrelation between the refractive index and iodine number was noted, and the two were plotted against each other. As is shown in the graph, the figures, with very few exceptions, fall within two or three points of a straight line. It will be further noted that the constants on the oils of known purity previously mentioned
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all fall on or near this line and, moreover, have values approaching both maximum and minimum figures. Another interesting and extremely significant point is the fact that some of the highest figures were those obtained during recent months, when oil prices were a t their lowest, and adulteration “to the analvtical limit” was not worthwhile. From the preceding, the rather contradictory conclusions are that, although in general the oils of highest quality have the highest iodine values and refractive indices, the constants of pure perilla oil (particularly the iodine value and refractive index) are subject to considerable variation, and low values do not necessarily mean adulteration.
LITERATURE CITED Materials, 1930 Standard
(1) Am. SOO. Testing
Specification D-125-23. ( 2 ) Pickard, G . H., The Paint Man’s Pocket Library, Am. Paint J. Co., Aug. 14, 1922. RECEIVED February 8, 1932.
Phenol-Acrolein Resins B. V. MAKSOROW AND K. A. ANDRIANOW Laboratory of Organic Chemistry, All-Union Electrotechnical Institute, Moscow-, L. S. S. R. HE purpose of this work is to investigate McIntosh’s reaction for the preparation of the resin “acrolite” ( 2 ) . The latter is prepared by heating for a long time a t 160180” C. a mixture of 100 grams of crystalline phenol and 70 grams of glycerol, 1 cc. of concentrated sulfuric acid being used as catalyst. Acrolites obtained in this way are almost Mack in acid media, purple in basic media, and highly hygroscopic. The authors made attempts to improve the technical properties of acrolite, first by using another catalyst, and second by varying the proportions of glycerol and phenol. Comparative experiments for the condensation of phenol with glycerol were carried out in the presence of various catalysts, such as sulfuric acid, 0-naphthalenesulfuric acid, acid potassium sulfate, and magnesium sulfate. The concentration of each catalyst varied from 0.02 to 0.5 per cent of the total weight of the reaction mixture. The concentration of the reagents varied in the following way: from 1mole of phenol per 1 mole of glycerol, to 3 moles of phenol per 1 mole of glycerol. The resulting products were, however, darkly colored and highly hygroscopic in all cases. I n the process of the formation of acrolite, two main reactions seem to take place simultaneously: (1) Glycerol is converted into acrolein which then condenses with phenol ; ( 2 ) glycerol is converted into polyglycerides which condense with phenol. Both suppositions are possible, since, under the influence of sulfuric acid, the formation of acrolein and the formation of polyglycerides take place simultaneously. Therefore, it is possible that acrolite is an intermediate form between phenol-acrolein resins and polyglyceride-phenol resins. Moureu has employed only basic catalysts in the condensation of phenol with acrolein, consequently the authors determined to study the influence of acid reagents on the condensation of phenol with acrolein. The first experiments with phenol-acrolein resins were carried out by Moureu, together with Dufraisse (,$). The authors used basic catalysts exclusively (3). Owing to their high elasticity, electrical stability, and the ease with which they
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can be worked mechanically, these resins were recommended for the molding of all kinds of electrical and radio parts. Kishi (1) condensed acrolein with phenol under pressure of 30 atmospheres in the presence of salts, such as zinc chloride, aluminum chloride, and other salts which, on being hydrolyzed, might give an acid reaction. Resins prepared by this method possess advantages over phenol-formaldehyde resin, in that they have greater elasticity and viscosity, and that their properties resemble those of synthetic rubber. On being mixed with oils, fats, and natural resins, they yield very viscous mixtures. From the Japanese patent it is not clear whether the condensation of phenol with acrolein may also be carried out in the presence of acid catalysts under atmospheric pressure anti, if so, what the resulting products would be. I n this conneation, i t was decided in these experiments t o compare the irifluence of acid and basic catalysts on the rate of condensation of phenol with acrolein, and to study the kinetics of the condensation process as influenced by time and temperature. PREPAR.4TION O F -kCROLEIS
;Icrolein was prepared in the following manner: Five-tenths kilogram of finely poir dered anhydrous acid potassium sulfate, 0.1 kg. of finely powdered anhydrous sodium sulfate, and 0.2 kg of anhydrous glycerol were thoroughly mixed in a &liter cylindrical vessel made of cop er. The vessel was closed, and the mixture allowed to st,and ?or 24 hours at room temperature. The reaction vessel contained three openings, one for a dropping funnel used for the addition of glycerol, the second for a mechanical stirrer propelled by an electrical motor, and the third for a condenser. The other end of the condenser was connected by means of an adapter to a large two-necked flask, heated on a water bath to 70-80” C. This flask was connected with another condenser, the second end of which was connected with another two-necked flask, used as a receiver for acrolein. The latter flask, through its second neck, was fitted with a reflux condenser, to the upper end of which a calcium chloride tube was attached. In the first condenser the circulating water was heated t o 4050” C.; in the second, colder water (about 17-20’ C.) was used. The mixture in the copper vessel (after standing for 20 to 24
