and, a t coiwntrations above that required for monolayer completion, the plate numbw will be inversely related t o sample size. (For cholesterol acetate, this concentration is below 1 mg. per nil.) The colunin a m i includes the considerations of pore diameter (and should eventually be extended to pore-size distribution) but i. also likely to include the surface energy and composition. The sample area depends primarily on the molecular area and sample size, but in addition is affected (in the case of t’he planar sterol niolecule) by the nsis of orientation. From surface film and x-ray data (1, I d ) , three alternative areas, 40,90, or 140 sq. A, appear reasonable for the cholesterol acetate molecule, depending on whether it is oriented across the ester end, along the bottom edge of the ring structure, or lying flat in the plane of the ring structure. I t seems unlikely that differences in ring structure could be detected as they have been if the sterol adsorbed on the surface only a t the ester grouping: thus a n area of 40 sq. -4.would appear to be too low. The molecular areas of cholesterol acetate in Figure 2 have, as indicated, limiting values of 210 and 105 sq. A., which are within the upper range of the estimates. Further studies are being carried out to map the apparent molecular area as a function of sample size, surface composition, and degree of activation. These studies should permit a more in-
formed estimate of the probable axis of orientation under these conditions. It appears possible to establish several guide lines for the planning of adsorption chromatographic separations from the information presented here. I n separations of a series of compounds differing in adsorptive energy, selection of the appropriate silica gel will be determined by the molecular areas of the substances: if these are low, the fine-pore gel offers a larger surface area per gram and a higher degree of resolution than a large-pore gel. If, on the other hand, the molecular areas are large, better fractionation per square meter of column area is achieved by using a large-pore gel where the apparent molecular areas are closest to the actual values. The possibility of retardation or “sievingJJ effects in small-pore gels should not be overlooked, since these may produce changes in separation factors which outweigh considerations of column efficiency. ACKNOWLEDGMENT
The author is indebted to Robert Waters and the American Oil Co. for their generous provision of the analyses of surface areas, and thanks Herman E. Ries, Jr., American Oil Co., and S. A. Greenberg and D. L. Kantro, Portland Cement Association, for their many helpful and informative discussions.
LITERATURE CITED
( 1 ) Adam, X. K., Danielli, J. F., Haslewood, G. A., Marrian, G. F., Biochem. J . 26, 1233 (1932). ( 2 ) Brunauer, 8., Emmett, P. H., Teller, E., J . Am. Chem. SOC.60, 309 (19?8). (3) Brunauer, S., Kantro, D. L., I$eelse, C. H., Can. J . Chem. 34,1483 (1956). (4) Dzis’ko, V. A . , Vishnevskaya, A. A., Chesalova, V. S., Zhiir. Fiz. Khim. 24, 1416 (1950). ( 5 ) Iler, R. K., “Colloid Chemistry of Silica and Silicates,” p. 127, Cornell University Press,(?thaca, X . Y., 1955. ( 6 ) . Kiselev, A. V., Structure and Proper-
ties of Porous Materials. Prcceedings of Tenth Symposium of Colston Research Society,” D. H. Everett and F. s. Stone, eds., p. 195, Academic Press, New York, 1958. ( 7 ) Klein, P. D., Jansaen, E. T., J. Bid. Chem. 234, 1417 (1959). (8) Lovern, J . A,, Biochem. J . 63, 373 (1956). (9) Lovern, J. A,, Olley, J., Hartree, E. F., Mann, T., Ibid., 67,630 (1957). (10) Morrison, M., Stotz, E., J. Bioi. Chem. 213, 373 (1955). (11) Resnik, F. E., Lee, L. A., Powell, P. A., ASAL. CHEW27, 928 (1955). (12) Schulze, G. E. R., Z. physik. Chem. A171,436 (1934). (13) Shull, C. G., J. A m . Chem. SOC.70, 1405 (1948). (14) Stokes, R. H., Robinson, R. A., Ind. Eng. Chem. 41, 2013 (1949). (15) Wren. J. J.. J . Chromatoa. 4 , 173 (i960). ’ (16) Zhdanov, S. P., Doklady Akad. h’auk S.S.S.R. 68,99 (1949).
RECEIVEDfor review June 5, 1961. Accepted August 31, 1961. Division of
Analytical Chemistry, Symposium Honoring H. H. Strain, 139th Meeting, ACS, St. Louis, Mo., March 1961. Work performed under the auspices of the U. S. Atomic Commission.
Continuous Separation of Gaseous Mixtures by Thermal Gravitational Diffusion HARLAN D. FRAME, Jr., JAMES R. KUSZEWSKI, JOHN F. BINDER, and HAROLD H. STRAIN Chemisfry Division, Argonne National Laborafory, Argonne, 111.
b For the continuous separation of gases by thermal gravitational diffusion, a rectangular diffusion cell (internal dimensions, 51 X 51 X 1 cm.) has been constructed and tested. For the thermal gradient, one large wall was provided with a water jacket and cooled with tap water. The opposite large wall was heated against a specially wound, vertical electric furnace. Gas flow through the vertical diffusion chamber was horizontal. This arrangement provided three mutually transverse driving forces-therma I gradient, gravity, and gas flow. Separations were made in diffusion cells with a structure-free diffusion chamber, with a chamber containing loosely packed silica fibers (vertically aligned), and with a chamber contain-
ing porous stainless steel barriers (also vertically aligned). The structure-free cell produced the best heliumnitrogen separation, the cell with silica fibers the best nitrogen-argon separation, and the barrier cell the best neon isotope enrichment. No significant dependence of the separations upon flow was found in any of the cells with flow rates from no flow to about 9% of the total internal volume per minute (IS0 ml. per minute at room temperature).
G
thermal diffusion-the differential migration or transport of molecules in a mixture in a thermal gradient-was predicted b y Enskog (6) and Chapman (2) and confirmed by Chapman and Dootson (3) in the second ASEOUS
decade of this century. When a thermal gradient is imposed upon a mixture of neutral molecules, the concentration of the light gas increases toward the hot wall and the concentration of the heavy gas increases toward the cold wall. The separatory power of the thermal gradient is enhanced by convection in a two-force (thermal gradient plus gravity) system as in the hot wire column of Clusius and Dickel (4). This arrangement made possible a practical analytical application of the phenomenon. Brewer and Bramley (1) used two concentric tubes for a thermal gradient column. The two-force system has also been extended by utilization of a third force, gas flow, in these columns, but withdrawal rates have been low or the process has been discontinuous. ExVOL. 33, NO. 12, NOVEMBER 1961
* 1741
tenaive studies of the theory (6-8) and practice ( I O ) of thermal diffusion columns hsve been reported. The development of a n effective] continuous, thermal diffusion procedure was thought to be possible through use of a third force, gas flow, perpendicular to temperature gradient and gravity (9). Two flat parallel vertical walls with a thermal difference should provide the two perpendicular forces, thermal gradient plus gravity. With this arrangement] the small, light molecules migrate toward the hot wall and upward; the large, heavy molecules toward the cold wall and downward, as shown schematically in Figure 1. Because the flow vector is dependent only upon the cell geometry] a thermal diffusion cell was designed so t h a t the flow vector would be perpendicular to the two other force vectors. EXPERIMENTAL EQUIPMENT
The thermal gravitational diffusion apparatus consisted of the thermal diffusion cell (with three modifications of the diffusion chamber), a large electrically heated surface or furnace, and a hydrodynamic system for the uniform, metered circulation (and sampling) of the gases. The assembled apparatus is shown diagrammatically in Figure 2. The thermal diffusion cells were rectangular (external dimensions] 55.9 X 55.9 X 3.1 em.). They were constructed of welded stainless steel. Each cell had one double wall through which tap water was circulated to provide the cold wall. The construction of the cells is indicated in Figure 3. The vertical cross section indicates a 3,/8-in~h plate, P , for the hot wall, which in operation lies flush with the vertical furnace surface;
vertically centered l / 2 inch from the left boundary of the chamber, I , and three effluent ports, E, 1/1 inch from the right edge, one vertically centered, the other two I / 2 inch from the top and bottom of the chamber. FOUI ports at the bottom, served as inlets for the t a p water to the uater jacket, and nine ports a t the top, TV0, served as outlets. The only significant differences among the niodifications of the three diffusion cells lay in the internal structure of their diffusion chambers. One cell had no internal structure save nine quartz spacing rods to perniit evacuation without wall collapse and possible ensuing seam rupture. The second was the same as the first, except that 219 grams of quartz fibers (diameter ca. 0.001 inch) were placed in the chamber with the fibers aligned vertically. These fibers occupied only 3.2% of the total internal volume. The third cell incorporated 21 sintered porous stainless steel (mean pore opening 165 microns) barriers inch thick, spaced 2 em. apart and aligned vertically. These were held in place by channel grooves milled into the thick, hot wall and by two right-angle braces around the remainder of the perimeter of the barrier, including the top and bottom walls. The braces were tack-welded to these walls. The positions of these porous barriers, U, are shown in the horizontal cross section of Figure 3. The porous barriers offered negligible resistance to the gas flow under the experimental conditions. Calculated a? solid material, these
Force Vectors:
Migrotion Paths:
$'
-
'.
P
0 I'ight 3 molecules
+
0
I
0.
heavy molecules
0
8
iI Figure 1.
Migration mechanism
the gas diffusion chamber proper, D (dimensions] 51 X 51 X 1 em.), and an outer water jacket for the cold wall, J . The hot wall plate had 13 thermocouple wells, T, each 4 inches deep by inch, and a channel groove, G, 1/4 inch deep by inch wide, milled into the external face of the plate near each edge to relieve strain during heating and to retard heat flow to the perimeter. Each of the cells was eqkipped with several gas ports leading through the water jacket into the diffusion chamber. For these ports 1/4-inch stainless steel tubing was welded to the outer wall of the water jacket and flush with the inner cold wall of the diffusion chamber. All welds were vacuum-tight] as tested with helium. Although more ports mere provided] only four ports have been utilized thus far: one influent port
c
I
"
G
P
.
................ .
I
I,,,,_
, i : : . i i .
01 ';t..'-.;;-.;'
Wi
Figure 3. B. C. E. F. G. 1.
25-ml. burets Gas collectors (with manometers) Gas effluent ports Insulated edge of furnace face Gas supply for preparing mixture in RI Gas influent port M . Gas mixture fcr deaeration of water in collectors and reservoirs Q. Dry ice trap RI Mixing reservoir R2 Working reservoir (with manometer) Sg Effluent sampling devices 5 1 Influent sampling device V. Vacuum source X . Variable-bore Teflon stopcocks Arrows show gas flow from Rz through D to C during separation
1742
ANALYTICAL CHEMISTRY
Structure of cells
Righf. Vertical cross section Cenfer. Cold wall face 13 thermocouple wells Upper. Horizontal cross section of porous barrier cell D. Diffusion chamber E. Gas effluent ports G. Stress-relieving groove 1. Gas influent port 1. W a t e r jacket P. Heated plate T. Thermocouple wells U. 2 1 porous barriers WO. 9 water effluent ports Wi. 4 water influent ports
---
barrieis occupied 6.5% of the internal volume of the cell. The electric furnace had Nichrome windings recessed 2 mm. into ceramic refractory, which was insulated behind with firebrick. The windings were in four sections, arranged one above the other. Each section consisted of a single winding, continuous through nine horizontal rous. The current in each of these four sections u a s controlled by an adjustable transformer. A special hydrodynamic system was devised t o ensure uniform, metered gas flow through the diffusion chambers. Gravity water flow from the upper gas collectors, C (Figure 2), into the lower gas reservoir, Rz, forced gas through the diffusion cell. Floaing into the reservoir, the water from each collector passed through a variable-bore Teflon stopcock, X, and through a 25-ml. buret, B. Each buret was equipped with a bypass from its top directly into the reservoir. The gas mixture was forced from the iekervoir through: a n acetone-dry ice trap, Q; one of the influent sample tubes, S I (from bottom to top); the influent poit, I , the diffusion chamber, D; the effluent ports, E , the effluent sample tubes, S E (from bottom to tor, I : and into the gas Collectors, c. The four sampling devices permitted intermittent sampling of the gas stream, with minimal interruption, by means of two parallel sampling tubes and two three-way stopcocks, arranged as shown in Figure 2. All sampling devices were identical. The influent sampling device could be evacuated n-ith the vacuum pump, V . 'l'his prevented the introduction of air into the chamber when new sample tubes were placed in teni. .ill parts of the circulating system through whirh gas passed prior to the effluent snrnplers were made of borosilicate glass n.ith ground joints. The sample tubes were connected with standard-taper joints at the upper end and rubber stoppers a t the lower ehd. Tjrgon tubing was used for gas flow between the effluent sampling devices and the gas collectors and for water flow from the collectors to the Teflon stopcocks. ;In adjunct to the gas f l o s~j d e n i was the gas mixing reservoir, R1, in which the gas mixture was first prepared prior to its introduction into the working reservoir, Rn. d 2-liter gas pipet (not shon-n in drawing] served to mensure the gases into the mixing reservoir. A sepnrate flowmeter-mixer provided a gas mixture of approximate comliosition for de-aeration and saturation of the water in the collectors and reservoirs. The temperature of the hot wall a t the points indicated in Figure 3 was deterinincti n-ith 13 Chrome1 Alumel thermocouples. I
,
,
-
PROCEDURE
The two reservoirs and three collectors were nearly fiiled with freshly distilled water. The gas misture, from the flowmeter-mixer, n-as bubbled through the water for periods in exccss
of 18 hours. The two reservoirs and the three burets were then filled completely with water. Equal volumes of the gases (total volume of 14 liters) were measured into the mixing reservoir, R1, After 30 minutes, allowed for mixing the components, the mixture was introduced into R2, The system, from a post-reservoir stopcock to the effluent samplers, was evacuated to 10 to 20 microns. The gas mixture was introduced into the evacuated system, and the influent stopcock a t SI closed. The current was turned on in the heating coils; the coolant water was turned on; and one or more effluent stopcocks were opened to allow an escape for the expanding gas. This "bleeding" of the cell was acconiplished through the center effluent port alone, the upper and bottom effluent ports together, or all three effluent ports. When the cell had reached constant, nearly uniform temperature, the remaining effluent ports were opened and the influent system was opened. During this operation, care mas taken t o ensure a higher pressure in the influent system to prevent introduction of contaminating gases and water vapor into the cell via the effluent ports. Again, a careful balance was maintained in effluent flow, just as in the bleeding operation. r a t e r flow was started simultnneou~lv in the two or three effluents used and the flow rate equalization begun. Flow rates were measured using the 25-ml. burets and a stopwatch. The variablebore stopcocks permitted flow equalization within 2% in 10 to 20 minutes. Uniform gas flow was maintained for periods of 2 t o 12 hours. During this time a volume of gas about 1.5 to 5 times the volume of the chamber (2600 cc.) flowed through the cell. Three sets of samples were taken, u ~ u a l l yafter one third, two thirds, and all of the elapsed time. With no gas flow (total reflux), samples were taken after the chamber had been closed off a t the conqtant, operational temperature for 18 to 7 2 hours. These samples a e r e collected by evacuating one tube of the effluent sampling apparatup. A vacuum line with a stopcock and a standard-taper joint was coupled to the upper attachment for the other sample tube. The evacuated section included the volume from the effluent stopcock, through one side of the sampling device, to the calosed stopcock on the vacuum linp. The effluent stopcock was then opened, filling the sample tube. Since the evacuated voluiiv was less than the volume of the effluent tube from the furnace to the samplcr, an esperinimt was run in which a series of samples was taken as above. A sequence of four samples exhibited R regular change which totaled 0.5% in 66%-pn amount approximating the reliability of the analytical method. At the beginning of the experiment, pressure in the system was set a t 75 to 150 mm. of water (above atmospheric pressure) as observed on the manometers on each of the collectors and on the reservoir. In no case was there an appreciable change in pressure (more
than 10 mm. of water) during the experiment. Occasionally a pressure change was observed during a total reflux waiting period. This was ascribed to a change in barometric pressure or slight changes in chamber temperature All gases and gas mixtures were analyzed with a mass spectromater, a Consolidated Engineering Corp. Model 21620. I
RESULTS AND DISCUSSION
Each of the three diffusion cells was tested wibh four gas mixtures-He-Nz (1 : 1), an extreme difference in molecular weight; N2-Ar (1: l ) , a smaller difference in molecular weight; He-NzAr (1:1:1), to test the effect of a threecomponent system; and natural Ne (90.8% Nez0, 0.26% NeZ1,8.9% NeZZ), to test for isotope separation efficiency. Each of the effluent streams as well as the influent stream was analyzed a t three intervals, as noted above. The variance in the three analyses for a given sampling position rarely exceeded 1 part in 50. Occasionally, a leak in the system permitted air to leak int,o the snmplcs. Results with nitrogen readings in excess of 1% or, alternatively, oxygen readings in excess of 0.33% were discarded. Several hot-wall temperatures were used in the more than 60 experiments carried out to date. The temperature gradients re1:orted in Table I are based on the highest value of the 13 thermocouple readings (Figure 3) and the cold wall temperature of 15" i 3" C. Comparative data from typical esperiment,s with the three modifications of the cells are summarized in Table I. Comparison of the separation fnctor, q, determined under similar conditions, shows that the resolving power varies rvith temperature, the gas misture, and the internal structure of the cells. For the separation of He-N2, the structure-free cell was very much more effective than the porous-barrier cell, which was mole effective than the fiber-filled cell. For KZ-Ar,the fiber-filled cell was slightly more effective t,hanthe structurefree and porous-barrier cells. For Ne2oNe22, the porous-barrier cell was significantly better t'han the structurefree and the fiber-filled cells. For the He-N:-Ar system the resolving power of the cells was similar to that observed in the He-K2 sj,stem. The gases behaved largely as a binary system, the N: and il.r migrating together. Some NC-Ar wparation was present, however, as indicated by their 4 values. There was a small i,elative enrichment of r\;2 a t the center effluent port. The sequence of resolving rowers for the three cells was consistent in each of the temperature ranges indicated in Table I . I n a given esperiment, temperature at the 13 points shown in Figure 3 was VOL. 33, NO. 12, NOVEMBER 1961
1743
l
l
u 3680396
342.388
2 6 7 0 368
247
342
Figure 4. Typical temperature distribution in structure free and porous barrier cell experiments 0 Positions of reading points Porous-barrier cell readings to left of dot; structure-free cell reading to right I, E, Influent and effluent port positions Double lines. Boundaries between heating units
not uniform. The temperature also varied n-ith the internal structure of the cells as shown in Figure 4. This temperature variation was greater in the stainless steel barrier cell than in the structure-free cell, presumably because of the heat conduction by the barriers. K i t h the porous-barrier cell, the temperature a t the upper center thermocouple was always significantly higher than that a t the other thermocouples. The temperature a t a given point in any cell did not vary more than 2" C. in a 6-hour period. Because of the irregular temperature distribution in the barrier cell, the separatory power of the barrier and structure-free cells for the He-Kp and Se20-SeZ2mixtures was tested with the temperature distribution in the structure-free cell made nearly as irregular as that in the barrier cell. The results from the structure-free cell experiments run with the usual temperature distributions are designated by B and D in Table I; with the imposed, irregular temperature distribution, by A' and C'. The corresponding experiments with the barrier cells are labeled A and C. The maximum temperature gradients, At, for these six experiments are given in Table I. The corresponding minimum temperature gradients were: He-Sp, 165" C. (barrier), 180" (imposed irregular, structure-free), 240" (usual, structure-free) ; Ke2~-Sez2.215" (barrier), 240" (imposed irregular, structure-free), 346" (usual, structure-free). The data for the three He-N? experiments (A,-4', and B in Table I) show that the resolving power of the structure-free cell decreased with irregular distribution of temperature (A'). But even with this decrease in the separatory power, the structurefree cell remained more effective than
w-
0
1744
ANALYTICAL CHEMISTRY
the barrier cell. Likewise, the imposed irregular temperature distribution in the structure-free cell decreased the Ne22 enrichment ((2’). Here, by contrast, the difference between the effectiveness of the structure-free cell and of the barrier cell was increased. Early in our investigations, the HeNz separations in the fiber-filled cell were found to be independent of the flow rate. No decrease in separation was observed between 1 and 16 ml. per minute per effluent port. Later, experiments were conducted consecutively (to ensure the same temperature distribution) on the He-Ns and Ne20Nez2 systems, each in the structurefree and porous barrier cells. These four pairs of experiments, in which the principal variable is the flow rate, are indicated by brackets in Table I. In the He-N2 system, a slight decrease in efficiency was effected by increasing the flow rate from 10 to 50 ml. per minute per effluent port. This decrease can scarcely exceed the experimental and analytical errors. With the Ne20Nez2 enrichment, the small changes were in the opposite direction-Le., the faster flow rate was accompanied by a slightly greater enrichment. This
150 ml. per minute flow rate was measured a t room temperature. In the case of a mean gas temperature in the chamber of 200” C., this represents a volume of 236 ml., or 9% of the total internal volume. Total reflux samples were taken in most of the experiments included in Table I. The analyses from these samples did not vary appreciably from the flow samples. The results in Table I show t h a t the separation factor increases with temperature gradient. This increase occurs in all three binary systems and with the three modified cells. The different separation factors for the three cells with the same gas mixture are believed to be due to the differences in the chamber structure. The order of these separation factors changes from one gas mixture to another, however. This phenomenon is thought to be associated with the nature of the gas molecule-wall collision and the ratio of such collisions to intermolecular collisions. The “nondependence” between separation factor and flow rate is probably due to the long flow path versus the small interwall distance of these cells’ geometry.
ACKNOWLEDGMENT
The authors thank C. E. Plucinski for the mass spectrometric analyses. LITERATURE CITED
(1) Brewer, A. K., Bramley, A., Phys. Rev. 55,590 (A) (1939). (2) Chapman, S., Phil. Trans. 216A, 279 (1916).
(3) Chapman, S., Dootson, F. W., Phil. Mag. 33,248 (1917). (4) , . Clusius. K.. Dickel, G.. Naturwissenschaften 26. 546 (1938). (5) Eiskog, D., Physik. 2. 12, 56, 533 (1911). (6) Furry, W. H., Am. J. Phys. 16, 63 (1948). (7) Herefeld, K. F., Smallwood, H. M., pp. 166-85, in “Treatise on Physical Chemistry,” Vol. 2, H. S. Taylor, S. Glasstone, eds., Van Nostrand, New York, 1951. (8) Jones, R. C., Furry, W. H., Reus. Modern Phys. 18, 151 (1946). (9) Strain, H. H., Murphy, G. mi., ANAL. CHEM.24,50 (1952). (10) Thomas, W. J., Watkins, S. B., Chem. Eng. Scz. 5,34 (1956).
RECEIVEDfor review July 11, 1961. Accepted September 11, 1961. Division of Analytical Chemistry, 139th Meeting ACS, St. Louis, Mo., March 1961. Based on work performed under the auspices of the U. S. Atomic Energy Commission.
Hydrogenation of Linolenate Comparison of Products from Trilinolenin and Methyl Linolenate by Use of Countercurrent Distribution and Gas-Liquid Chromatography C. R. SCHOLFIELD, E.
P. JONES, and H. J.
DUTTON
Northern Regional Research laboratory, Peoria, 111.
b Countercurrent distribution (CCD) with a hydrocarbon-acetonitrile solvent system and with 650 transfer stages is effective in resolving a mixture of octadecatrienoate, octa deca dienoa te, octadecenoate, and octadecanoate methyl esters obtained when methyl linolenate is reduced with 1 mole of hydrogen. However, this system does not separate the isomeric monoenes and dienes that differ in position and geometric configuration of their double bonds. Gas chromatography (GLC) on a 200-foot capillary column packed with Apiezon L is effective in fractionating the isomers but only after their prior separation into monoene and diene classes by CCD. These two forms of differential migration (CCD and GLC) have been applied to the catalytic hydrogenation of linolenate to learn whether the steric restrictions, imposed by triester struc-
ture of triglyceride oils compared to monoesters, influence the course of the hydrogenation reaction and the number of isomers produced. The great complexity of reactions and products in hydrogenation mixtures is effectively demonstrated by these techniques; however, little difference could be attributed to the tri- or monoester structure of the linolenate.
M
esters of fatty acids are convenient materials for studying the mechanism of catalytic hydrogenation. They are more easily prepared in pure state than are the corresponding triglyceride oils and, without a subsequent alcoholysis step, are immediately amenable to analysis by gas chromatography. Because of the commercial significance of hydrogenation of triglycerides and because of the ETHYL
need for relating work on methyl esters, a comparison was made of the fatty acid composition of methyl linolenate (methyloctadecatrienoate) (6) and of its corresponding triglyceride, trilinolenin, after hydrogenation under similar conditions. It was anticipated that, in addition to differences in rate of hydrogenation, steric restrictions imposed by the triglyceride structure, compared to the mono ester, would affect the adsorption of double bonds close to the carboxyl end of the chain. Further effects on the course of the reaction, the products formed, and the geometric configuration of residual bonds were expected. The experimental approach, in brief, consists of catalytically adding 1 mole of hydrogen per mole of octadecatrienoic triglyceryl ester and of separating the trienoic, dienoic, and monoenoic unsaturated methyl esters by a 650-stage VOL 33, NO. 12, NOVEMBER 1961
1745
