218
lNDUSTRIAL AND ENGINEERING CHEMISTRY
for which pure steam was generated, show much less variation. The above correlation would indicate, in the light of Kirkbride's discussion, that the condensate film was always in viscous flow. This is probably true for the upper portion of the tube, where the amount of condensate was small. But for tubes of such lengths as were used in these three investigations, the accumulation of condensate should result in turbulent flow on the lower portion of the tube, even with small values of At,. This offers an explanation for a smaller negative slope of the curve than would be predicted theoretically for viscous flow. Apparently the rate of heat transfer from condensing steam is affected, but not controlled, by turbulence in the condensate film. With sufficiently high values of At,, it is probable that the turbulence in the film would become of increasing importance. However, the data used here are within the range of most commercial operations. From the correlation here developed it would appear advisable to use shorter rather than longer tubes in vertical condensers and evaporators, in so far as heat transfer on the steam side is concerned.
VOL. 31, NO. 2
Nomenclature D
= diameter of tube, ft.
L
length of tube, ft. steam-film temperature difference, O F. weight of condensate per tube, lb./hr. viscosity, lb./(ft.)(hr.). = density, Ib./cu. ft. = latent heat of condensation, B. t. u./lb.
acceleration of gravity, ft./(hr.) (hr.) 8,k 1 steam-film coefficient, B. t. u./(hr.)(sq. ft.)(" F.) = thermal conductivity, B. t. u./(hr.)(sq. F./ft.). ft.)(O
= At, = W = fi = p
X
Literature Cited ( 1 ) Badger, Monrad, and Diamond, IND.ENG.CREM.,22,700 (1930). (2) Fragen, doctorate thesis, Univ. Mich., Feb., 1936. (3) Hebbard and Badger, IND.ENG.CHEM.,Anal. Ed., 5, 359 (1933). (4) Hebbard and Badger, Trans. Am. Inst. Chem. Eng~a.,30, 194
(1933).
Kirkbride, Ibid., 30, 170 (1933). (6) McCormick, Ibid., 30, 216 (1933). (7) Stroebe, Baker, and Badger, IND. ENG.CHEM.,31, 200 (1939). (5)
November 3, 1938. Preaentad before the meeting of the Amenoan Institute of Chemioal Engineers, Philadelphia, Pa., November 9 to l l v 1938. RmCmIWD
Composition and Drying Rates
of Soybean Oils H. R. ICRAYBILL, A. W. BLEINSMITH, M. H. THORNTON
AND
Purdue University Agricultural Experiment Station, Lafayette, Ind.
Analyses of Soybean Oils and Drying Rates When Mixed with 10 Per Cent of Tung Oil and Driers v
HEN domestic soybean oil was first offered on the American market, much of it was inferior to that imported from the Orient (3, 11). Several explanations were offered to account for this difference. Junker (7) stated that modern methods of expressingremove more of the nonfatty constituents along with the oil than the crude WIanchurian presses. Fickard (11) and Eastman (3) attributed the poorer quality of the domestic oils to inefficient filtering. Gardner (4) found larger amounts of foots in some of the domestic oils, indicating that the oils had not been permitted to settle long enough. The statement has been made frequently that there is a large variation in the drying rates of domestic crude soybean oils. The Detroit Paint and Varnish Club (a) in 1934 concluded that the variations in induction period of crude soybean oils is due to the presence of antioxidants. Treatment of the crude oils with various oxidizing agents reduced the induction period and increased the drying rate of the oils. I n connection with analyses and drying rate determinations made on samples of soybean oil for the Finished Materials Standards Committee of The American Soybean Manufacturers Association in 1935, the drying rates of the oil samples*
W
Eighty-seven samples of commercial soybean oil were collected at intervals of two or three weeks from thirteen different soybean processing plants during the first six months of 1936. These plants represent three processes-expeller, hydraulic, and solvent. Analyses of the oils were made as follows: per cent of foots, per cent of break (Gardner method), per cent of phosphatides, acid number, iodine number, refractive index, and drying time before and after removal of the phosphatides and associated compounds. There was a close correlation between the Gardner break and the percentage of phosphatides of the crude oils a&calculated from the phosphorus content of the oils. There was a correlation between the average phosphatide contents of the samples of oil from the different plants and the drying rates. No correlation was found between the phosphatide content of the crude oils and the drying rates of the oils from which the phosphatides had been removed. The results show that the presence of phosphatides retards the drying rate of the crude oils but that other factors are also involved.
FEBRUARY, 1939
INDUSTRIAL AND ENGIhEERING CHEMISTRY
219
were increased and showed much less variation following removal of the crude phosphatides. Scofield (12, 13) found that the addition of tung, oiticica, p.erilla, or fish oil to soybean oil with lead and manganese driers increased the drying rate. During the first six months of 1936, eighty-seven samples of crude soybean oils were obtained from twelve soybean mills. This paper gives the results of the analyses and the drying rates of these samples when mixed with 10 per cent of tung oil and lead and manganese driers before and after removal of the crude phosphatides.
E.
Materials Samples of oil were obtained from eight mills using the expeller process. The samples from all of these mills, with one exception, were the filtered crude oils. In one plant ( A ) the samples were clarified to remove most of the crude phosphatides. The samples from the two mills using the hydraulic process and the samples from one mill using the solvent (L) process were the filtered crude oils. Two sets of samples were submitted by another plant using the solvent process. One set of samples represented the filtered crude oils and the other set, the clarified oils. It was impossible t o determine definitely the varieties of beans and the definite locations where they were grown. In all cases t h e beans r e p r e s e n t e d yellow varieties and consisted largely of Illini, Dunfield, a n d M a n c h u varieties. In most cases the beans were grown in Illinois, Indiana, and Ohio.
FIGURE 1. RELATION OF AVERAGE CONTENT OF PHOSPHATIDES TO AVERAGE DRYINGTIME OF
CRUDEOILS
E , expeller; H,hydraulic; 8, solvent oils
Methods
.
/'
1 *
:
r
-
i
:
.
.3
r 4
6
5
Drying Time - Hours
FIGURE 2. RELATION OF DRYING 'hfE
r
PHOSPHATIDE CONTENT O F CRUDEOILS
TO
8
INDIVIDUAL
SAMPLES OF
T h e acid a n d iodine numbers (Wijs) were determined according to the methods of the Association of Official A g r i c u l t u r a l Chemists (1). The percentages of foots and the percentages of break were determined by the Gardner m e t h o d (6). T h e t o t a l phosphorus contents of the
TABLE I. ACIDNUMBERS, IODINE NUMBERS, AND REFRACTIVE INDICES OF SOYBEAN OILS No. of Plant Samples
Acid No. of Crude Oils A -
Min.
Max.
0.25 0.6 0.7 0.7 0.7 0.6 0.7
0.45 0.9 1.3 0.92 0.9 1.1 1.1 1.85
Refined 134.4 134.8 134.8 133.5 134.3 135.6 134.2 134.2
-
0
1.23
I
J
5 9
Hydraulic
1.1 1.0
1.8 1.5
1.5 1.2
131.4 132.8
132.9 130.0
134.9 135.2
135.9 135.3
132.7 133.9
133.7 133.5
1.4752 1.4747
1.4754 1.4753
1.4753 1.4751
K Ka L
S
Solvent
0.4 0.5 0.88
0.6 1.1 2.68
0.5
b
06
135.0 129,3 133.0
133.2 130.1 132.3
136.7 136.6 135.7
136 2 135.6 135 6
135.8 135.8 134.1
134.9 134.2 133.7
14744 1.4747 1.4739
1.4749 1.4751 1.4752
1.4747 1.4749 1.4744
D E F
H
6
7 4
8
0.7
0.8
1.92
Refined 133.2 134.1 133.6 132.1 133.4 134.1 132.4 131.5
Refractive Index of Crude Oils
-Av.Crude 133.9 134.9 134.9 134.4 134.4 135.4 134.7 134.2
4 5 6 14
B C
7
Av. 0.36 0.7 0.9 0.8 0.8 0.9
Iodine No. --Max.Crude Refined 135.3 135.7 135.3 135.3 136.2 136.4 135.4 134.4 135.5 135.5 136.2 136.6 135.0 135.4 135.4 135.8
Crude 132.3 134.3 134.1 132.2 133.7 134.9 134.5 133.1
A
Process Expeller
.7-Min.-
Min. 1.4745 1.4748 1.4748 1.4747 1.4744 1.4746 1.4750 1.4747
Max. 1.4752 1.4750 1.4751 1.4749 1.4751 1.4753 1.4752 1.4752
Av. 1.4749 1.4749 1.4749 1.4748 1.4747 1.4750 1.4751 1.4749
INDUSTRIAL AND ENGINEERING CHEMISTRY
220
TABLE11. CO~VPOSITIONAND DRYINQRATESOF CRUDE yoFoots in Crude Oils
No. of
r
Plant Samples Process A 7 Expeller E 5 C
D E F a H
7 4 4 5 6 14
I
J
6 9
Hydraulic
K
8
Solvent
Kr L
8
5
% Break of Crude Oils
' Min. Max.
REFINEDSOYBEAN OILS
Lecithin in Crude Oils * Drying Time, Hr. 1 , -Crude Oils-Refined OilsMin. Max. Av. Mia. Max. Av. Min. Max. Av.
70
Min.
Max.
Av.
0.0 1.0 0.3 0.6 1.1 0.4 0.3 2.1
0.2 2.0 1.6 2.1 2.0 1.0 1.0 5.1
0.05 1.4 0.87 1.1 1.7 0.8 0.6 3.5
0.01 0.30 0.24 0.27 0.27 0.33 0.30 0.45
0.02 0.44 0.40 0.31 0.34 0.48 0.70 1.10
0.02 0.37 0.29 0.29 0.30 0.38 0.43 0.57
0.16 1.36 0.96 1.15 1.18 1.37 1.23 .1.97
0.62 1.93 1.60 2.22 1.76 2.28 2.43 3.26
0.36 1.65 1.28 1.54 1.39 1.70 1.74 2.36
2.25 3.25 3.00 2.5 3.25 2.75 2.50 3.50
3.5 6.0 4.25 4.75 4.50 3.50 3.75 8.75
2.68 3.95 3.46 3.69 3.69 3.05 3.25 4.39
2.25 2.50 2.25 2.25 2.75 2.25 2.50 2.50
3.0 4.0 3.0 2.76 4.00 3.00 3.00 4.00
2.46 3.05 2.71 2.50 3.19 2.66 2.75 2.84
3.4 4.0
9.4 7.6
5.1 5.5
0.57 0.47
0.59 0.76
0.58 0.61
2.13 1.81
2.98 3.43
2.56 2.65
3.50 4.00
7.25 5.25
5.30 4.64
2.00 2.25
3.60 3.75
2.80 2.81
0.0 0.0
0.4 0.9 4.5
0.2 0.3 1.01
0.02 0.00 0.02
0.15 0.11 0.30
0.07 0.03 0.12
0.25 0.24 0.13
0.63 0.51 1.06
0.37 0.31 0.67
2.00 2.50 2.50
3.25 3.75 4.50
2.7 3.15 3.3
2.00 2.50 2.5
2.75 3.75 4.00
2.43 2.87 2.80
0.0
Av.
AND
VOL. 31, NO. 2
,**e*
The range in acid numbers of the forty-five samples of expeller oil from seven mills is 0.6 to 1.85. Seven samples of clarified oil from expeller mill A range in acid value from 0.25 to 0.45 with an average value of 0.36. The range in acid numbers of fourteen samples of oil from two hydraulic mills i s 1.0 to 1.8, and of sixteen samples from one solvent plant, from 0.4 to 1.1. In solvent plant L five samples show a range of 0.88 to 2.68 in a c i d number with an I average value of 0 a5 1.0 1.5 2.0 , 1.92. I n t h e Difference ~n Drying 7ime - Hours L latter plant the FIGURE 3. RELATION OF AVXYRAGE PHOSPHATIDE CONTENT OF CRUDE beans are treated OILS TO AVERAGEDIFFERENCEIN DRYINGTIMESOF CRUDEAND by a special REFINEDOILS process previous to extraction of the fat. No reoils were determined by the method described by Hallilation is evident 2.5 3.0 day (6),and for convenience the results were calculated as between the acid Drying Time -Hours lecithin. n u m b e r s and drying times of FIGURE4. RELATIONOF The drying rates were determined as follows: Twenty-two and AVERAGE PHOSPHATIDE CONthe oils. one-half grams of soybean oil were weighed into a 50-ml. beaker. TENT OF CRUDE OILS TO T h e iodine Two and one-half grams of raw tung oil were then added, and the AVERAGE DRYING TIME OF n u m b e r s of two oils were mixed thoroughly. Then 0.4167-gram of Nuodex REFINEDOILS manganese drier, equivalent to 0.10 per cent of manganese, was e i g h ty-seven stirred into the oil; 0.2605 gram of Nuodex lead drier, equivalent samples of crude t o 0.25 per cent of lead, was added with stirring. The oil mixture oils vary from 129.3 to 136.7. Refining the oils-produces no was applied to a smooth qlass plate (3 X 4 inches, or 7.6 X 10.2 cm.) by means of a Park s fJmo raph calibrated to yield a film significant changes in the iodine numbers. Differences in 0.003 inch (0.0076 om.) thick. t h e plate was then placed in a drying times of the oils show no significant relation t o differsloping osition (approximately 45" an le) in a cabinet at 27" C. ences in iodine values. The average iodine numbers of the in whici the humidity was maintainef approximately constant oils from the various mills, regardless of the type of process (about 55 per cent) by means of a large dish containing a saturated water solution of magnesium nitrate. An electric fan cirused, are very uniform. culated the air over the dish. After 2 hours the films were checked The refractive indices of the oils vary from 1.4739 to 1.4754. at half-hour intervals until they were dr to the touch. The refractive indices of the refined oils were determined; The crude soybean oils were refinec? by removing the crude but since the refining of the oils does not result in any sigphosphatides and associated compounds by adsorption on a solid nificant changes in the refractive indices, those results are not reagent. When heated t o 315' C., the refined oils showed no break and bleached to a very light color. Analyses of the represented. No relation is apparent between the refractive fined oils showed that the phosphorus-containing compounds had indices and drying times of the oils. The average refractive been removed almost completely. indices of the oils from the different mills are very uniform, regardless of the type of process used. Data The percentages of foots in forty-five samples of oil The acid numbers, iodine numbers, and refractive indices from seven expeller mills vary from 0.3 to 5.1. The average valuesfor thesevenmills range from 0.6 to 3.5. The percentof the oils are given in Table I ; the percentages of foots, break, and lecithin, and drying times, in Table 11. ages of foots in fourteen samples from two hydraulic mills
e
FEBRUARY, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
range from 3.4 to 9.4. The average values for the two mills are 5.1 and 5.5. The percentages of foots in sixteen samples from one solvent plant range from 0.0 to 0.9 per cent. The percentages of break of forty-five samples of expeller oils vary from 0.24 to 1.10. The samples of clarified oil from plant L show practically no break. The fourteen samples of hydraulic oils from two plants vary in percentages of break from 0.47 to 0.76. Sixteen samples of oil from one solvent extraction plant vary from 0.00 to 0.15 per cent of break. The percentages of phosphatides (expressed as lecithin) of forty-five samples of expeller oils from seven mills vary from 0.96 to 3.26, with an average value of 1.80. The average percentages of phosphatides of the oils from each plant range from 1.28 to 2.36. From the information available regarding varieties of beans and localities where grown, it is apparent that these differences are due chiefly to the manner of conducting the expelling of the oil. Smith and Kraybill (14) showed that the moisture content and temperature of pressing of the beans have a marked effect on the type of oil produced. Fourteen samples of oil from two hydraulic mills range from 1.81 to 3.43 per cent in phosphatide content. The average percentage is 2.62. The average percentages of phosphatides for the two mills are 2.56 and 2.65. The percentages of phosphatides of the sixteen samples from one solvent plant range from 0.24 t o 0.63, with an average value of 0.34. The drying times of fifty-two samples of expeller oils from eight mills range from 2.25 to 8.75 hours. The average drying times of the samples from these mills vary from 2.88 to 4.39 hours. The drying times of fourteen samples from two hydraulic plants range from 3.50 to 7.25 hours. The average times for the two plants are 5.30 and 4.64 hours. The drying times of sixteen samples of solvent extracted oils vary from 2.00 to 3.75.
Relation of Phosphatide Content to Drying Times In Figure 1 the average percentages of phosphatides of the samples of oil from each mill are plotted against the average drying times of the oils. There is a fairly close relation between the phosphatide content and drying time of the oils. I n general, the drying time increases with increase in phosphatide content. The percentages of phosphatides of the individual samples are plotted against the drying times of the individual samples in Figure 2. The relation between drying time and phosphatide content is not so close as when the average values are plotted, but the same trend is apparent as with the averaged values. This is due in part a t least to the inaccuracy of the method of determining the drying time. M7hen averages of the drying times are taken, the inrtccuracies of the values are reduced.
FIGURE 5. AVERAGEDRYING TIMEOF CRUDEAND REFINED OILS
22 1
The average phosphatide contents of the samples of oil from each mill are plotted against the average differences of the drying times of the crude and refmed oils in Figure 3. There is a fairly close relation between the phosphatide contents of the crude oils and the differences between the drying times of the crude and refined (crude phosphatides removed) oils. In general, the oils with the higher phosphatide contents show greater differences between the drying times of the crude and refined oils. No definite relation is apparent between the average phosphatide contents of the crude oils and the drying times of the refined oils as plotted in Figure 4. Figure 5 shows the relative average drying times of the crude and refined oils. There are large variations in drying times of the crude oils which practically disappear upon removal of the crude phosphatides. The average drying rates of the refined oils are very uniform.
I
L
Per Cent Pbosphatrdes FIGURE6. RELATION OF AVERAGE PERCENTAGE OF PHOSPHATIDES TO AVERAGE PER- . CENTAGE OF BREAEOF CRUDE OILS E , expeller; H , hydraulic; S,solvent oils
These data indicate that the phosphatide contents of the oils have an important influence upon their drying times. Since this relation is not nearly so close when individual samples are compared as when average values are used, and since there is some variation in the drying times of the r e h e d oils, it is probable that other factors also are important in influencing the drying times of the oil. Other substances such as pigments, gums, mucilages, and sterols are also r e moved with the phosphatides in the refining process employed. Olcott and Mattill (10) found that commercial preparations of “lecithin” have moderate antioxygenic action on refined cottonseed oil. They believe that the antioxygenic agent in these preparations is cephalin. They also found (8, 9) that the unsaponifiable fraction of many vegetable oils contains active antioxidants which they called “inhibitols.” It is impossible to state definitely from the data a t hand whether the true phosphatides or other constituents of the oils that are removed with the phosphatides are responsible for theeffects on drying times.
Relation of Phosphatides to Gardner Break A close correlation exists between the average percentages of phosphatides and Gardner break as plotted in Figure 6. Figure 7 shows that there is a close correlation between the percentages of phosphatides and Gardner break of the individual samples.
INDUSTRIAL AND ENGINEERING CHEMISTRY
222
VOL. 31, NO. 2
hydraulic oils from 1.81 to 3.43 with an average of 2.62, and of the solvent oils from 0.24 to 0.63 with an average value of 0.34. 8. The crude phosphatides of crude soybean oils have a marked influence on their drying times. In general, the drying time increases with increase in phosphatide content. The large differences in drying times of crude oils practically disappear upon removal of the crude phosphatides. I n general, the oils with the higher phosp h a t i d e contents show greater differences in drying times of crude oils and refined oils. 7. Drying time determinations of crude soybean FIGURE7. RELATION OF PHOSPHATIDE CONTENT TO PERCENTAGE OF BREAKOF INDIVIDUAL oils are of no value in deSAMPLES OF CRUDE OILS termining the drying qualities of the clarified or refined oils. Discussion 8. There is a very close relation between the percentage of phosphatides and percentage of Gardner break in crude Since the phosphatides of the crude soybean oils are resoybean oils. moved in the commercial production of nonbreak oils by clarifying or by acid or alkali refining, drying rate determinations on the crude oils are of no value in determining the Acknowledgment drying qualities of the clarified or refined oils. The large variations that occur in drying times of the crude soybean The writers desire to express their appreciation to the varioils are due chiefly to their variation in crude phosphatide ous companies operating the soybean mills for making availcontents. By removing the crude phosphatides, soybean able the samples for these studies. oils of rather uniform drying times are obtained. It should be remembered that the relative influences of both the crude Literature Cited and refined oils on the drying times of the finished products such as paints and varnishes may not be the same as the dry(1) Assoc. Official Agr. Chem., Official and Tentative Methods of ing times of the oils as measured in these studies. OpporAnalysis, 4th ed., pp. 410, 417 (1935). (2) Detroit Paint and Varnish Club, Natl. Paint, Varnish Lacquer tunity was not afforded to study these influences in the Assoc., Sci. Sect., Circ. 471, 321-8 (1934). hished products, Such studies are needed. (3) Eastman, W. H.,address given before Ann. Convention Am.
Summary 1. The acid numbers, iodine numbers (Wijs), refractive indices, percentages of foots, break, and phosphatides, and drying times were determined for eighty-seven samples of soybean oils before and after removal of the crude phosphatides. The samples were obtained a t intervals of several weeks during the first six months of 1936 from eight expeller, two hydraulic, and two solvent extraction plants. 2. No relation exists between the acid values and drying times of the oils. 3. The average iodine numbers of the oils from the different mills are very uniform, regardless of the process used in extracting the oil. Differences in iodine numbers show no significant relation t o differences in drying times. The refractive indices of the oils from the various mills are very uniform and show no relation to drying times of the oils. 4. The percentages of Gardner break of the expeller oils range from 0.24 to 1.10, of the hydraulic oils from 0.47 to 0.76, and of the solvent oils from 0.0 to 0.15. 5. The percentages of phosphatides (phosphorus content expressed as lecithin) of forty-five samples of expeller oils ranee from 0.96 to 3.26 with an average value of 1.80. of the
Soybean Assoc., Washington, D. C., Sept. 2, 1932. (4) Gardner, H.A., Paint Mfrs.’ Assoc. U. S., Circ. 67 (Aug., 1919). (5) Gardner, H. A., “Physical and Chemical Examination of Paints, Varnishes, Lacquers and Colors,” 7thed., pp. 747,751, Washington, D.C.,Inst. of Paint and Varnish Research, 1935. (6) Halliday, G. E., Oil & Soap, 14, 103-4 (1937). (7) Junker, M.,Allgem. Oel- u. Fett-Z~Q.,30,492-5 (1933). (8) Olcott, H.S., and Mattill, H. A., J. Am. Chem. SOC.,58, 162730 (1936). (9) Ibid., 58, 2304-8 (1936). (10) Olcott, H. S., and Mattill, H. A., Oil & Soap, 13,98-100 (1936). (11) Pickard, G. H.,“Soybean Oil,” St. Louis, Am. Paint Journal co. (12) Scofield, Francis, Natl. Paint, Varnish Lacquer Assoc., Sci. Sect., Circ. 519 (1936). (13) Ibid., 522 (1936). (14) Smith, R. L.,and Kraybill, H. R., IND. ENQ.CHEM.,25, 334 (1933). R~CPIV April ~ D23, 1938. Presented before the Division of Paint and Varnish Chemistry at the 96th Meeting of the American Chemiod Society, Dallas, Texas, April 18 to 22, 1938.
