SEPTEMBER, 1939
INDIJSTRIAL AND ENGINEERING CHEMISTRY
not be detailed here have shown that in the case of ethylene hydration the cost of acid concentration in the two-step process far more than offsets the cost of gas purification for the catalytic operation. On the other hand, in the erne of propylene hydration the authors are inclined to favor the two-step absorption and hydrolysis, particularly when the absorption step is accomplished by liquid-phase reaction (f8).
Literature Cited (1) Alphen. J. YSO, Rec. tmu. chim.,49,754 (1930). (2) Applehy. Glass. and Horsley, J . SOC. C h m . Id.. 56, 279T
1103
Ellis, "Chemistry 01 Petroleum Derivatives," Vol. 2.. pp. 28S97, New York, Reinhold Publishing Corp., 1937. Frenois, U. S. Patent 2,055,720 (1936). Lewis. I M . ,2,130,669 (1938). Metsar. Ibid., 2,021,564 (19351; 2,050,442,Reissue 20,505 (1937): 2,050,443, Reissue 20,474 (1937): 2,087.290 (1937): and 2,050.445, Reissue 20,739 (1938). Rowisnd and Wallin, Ibid.. 2.142.036 (1938). Sohumann and Aaton, J . Chem. Phw., 6,480 (1938). Shifflerand Holm,Jbid., 1351,740 (1934) and 2,052,806 (1936). Shiffler,Holm, and Anderson, Ibid.. 1,988,611 (1935). Stanley, Youcll. and Dymock, J . Soc. C h m . Id., 53, 205T (1934).
,109n l_"-.,.
(3) Bdoar, U. S. Patent2.044.417 (1936). (4) Dreyfus, Ibid.. 2.a45.842 (1936)arid 2,093,426 (1937).
P~EJ~NT boioie E D the Division of Petroleum Chemistry at the 97th Meeting of the American Ciiemical Society, Baltimore, Md.
ANTIOXIDANTS FOR CASTOR OIL GERALD 0. INMAN Rock Island ilrsenal, Rock Island, Ill.
C
ASTOR oil as a lubricant in ordnance niatdriel has proved very advantageous in certain instances, since it can be used in contact with rubber packings with no harmful effects on the latter. A disadvantage frequently encountered, however, is that, witlh age, the castor oil becomes oxidized, attacks brass parts, and causes undesirable corrosion. It is not nnconnnon for castor oil which bas been applied to a lubricator of a mechanism in storage to increase in acidity from a value of 2 to above 35 in two years. The green color which develops in the oil and on the lubricators is evidence of corrosion. These brass parts are attacked more rapidly by castor oil of high acidity than by oil of low acidity. It was with the hope of finding an inhibitor which would prevent the oxidation of castor oil that this work was nndertaken. Yamaguchi (4)subjected olive oil and castor oil to oxidation. Progress of the reaction via8 followed by the determination of the iodine number. He showed that the addition of minut.e amounts of diphenylhydrazine greatly prolonged the latent period and that the length of the latent period was approximately proportional to the quantity of diphenylhydrazine added. KO subsequent work has been reported on antioxidants for castor oil. However, considerable investigative work has been done by Tariaka arid Nakamura (8) on antioxidants of classes of oils such as linseed, soybean, cottonseed, and others. Phenols were arranged by tliesc authorsaccording to their antioxygenic activity as follows: pyrogallol, hydroquinone, catechol, anhydrous phloroglucinol, resorcinol, phloroglucinol dihydrate, and phenol. With nitro- and chlorophenol the activity depends upon the position of the group or atom. The action of aniline and its methyl, nitro, and chloro snbstitution products upon the oxidation of linseed oil was examined. The changes in properties were det,erinined by comparing the specific gravity, index of refraction, iodine number, and viscosity before and after treatment. Aniline, xylidine, 0- and ptoluidine are ant.ioxidants or pro-oxidants, meording to conditions.
The effect oi antioxidants on the autoxidation of fats has also been studied by Mattill (8). He st,udied the rate of oxygen uptake by a standard mixture of lard and cod liver oil in the presence of various aromatic hydroxyl derivatives. He observed that if there are two hydroxyl groups in the ortho or para position, the antioxygenic activity is high; that the meta compounds are inactive; and that alphanaphthol is a much more effective antioxidant than the beta derivative.
Experimental Procedure In this work the antioxygenic activity of the various compounds towards castor oil was measured by following the rise in acidity of the oil. The action was accelerated by passing oxygen through tho oil held a t an elevated temperature. The general layout of tlie apparttt~usis shown in Figure 1. The apparatus consists of two main parts-the gas measuring device which regulates the amount of oxygen going to each sample of oil and the constnnt.teniperature bath which holds tlie oil sample tubes. This apparatus is capable of handling six samples of oil at one time. The oxygen is drawn from a commercial cylinder of oxygen through the pressurereducing valve, shown at the left of Figure 1. From here the oxygen
INDUSTRIAL AND ENGINEERING CHEMISTRY
1104
is led to the back side of the metering panel where it is distributed to each of the six manometer tubes. For each sample of oil the oxygen must pass through a 6inch section of capillary tubing. The pressure differences of the two sides of these sections of capillary tubes are registered in the manometer tubes shown on the wooden panel in the central portion of Figure 1. These manometers were calibrated so that each sample of oil received the same amount
TUBEWITH BUBBLER TUBE FIGURE 2. OIL SAMPLE
of oxygen. The oxygen passed from this gas-measuring device through the rubber tubes down to the test tubes in the constant-temperature bath. Here the oxygen was led to the bottom of the test tube and released into the oil through porous sintered glass disks which were fused into the ends of the glass tubing. A better idea of the construction and use of these porous disks can be obtained from Figure 2. I n passing through these sintered disks, the oxygen was broken up into innumerable gas bubbles which gave intimate contact of the oxygen with the castor oil. The sintered disks were prepared according to the directions of Kirk, Craig, and Rosenfels (I). The constant-temperature bath consisted of a doublewalled steel vessel provided with 1inch of ground cork insulation. The bath was electrically heated and thermostatically controlled by a mercury thermoregulator and relay. Ethylene glycol was used as the heating medium in the bath. I n actual operation 0.1 per cent of each of the materials being tested as antioxidants was placed in its respective test tube, and 25 grams of castor oil were added. These samples were then placed in the constant-temperature bath and the rate of flow of oxygen was adjusted to 60 ml. per minute. The temperature of the bath was maintained a t 125" C. (257" F.). Measurements of the acidity of the castor oil were made a t approximately 6-hour intervals. At the end of 20 to 30 hours, the acidity of the control samples had risen to a rather high degree, and the tests were discontinued. It was necessary to stop some of the tests after a much shorter period because the castor oil with some of the antioxidants frothed to such a degree after 5-10 hours
TABLE I. ACID NUMBEROF CASTOROILWITH VARIOUSANTIOXIDANTS DURING ACCELERATED OXIDATION TEST Compound Pyrogallol Hvdroouinone Citeohbl 8-Hydroxyquinoline a - N a hthol Morpioline Phenyl-a-naphthylamine Diphenyl sulfide Diamylamine Control sample Glycine Benzvl aloohol Resoroinol p-Nitro henol .o-cresor) m-Cresol Thio-@-naphthol p-Thiooresol
-Acid 0 2.2 1.5 1.4 1.6 1.9 1.8 1.7 1.4 1.5 1.1 1.9 2.1 1.9 2.5 2.6 1.8 1.9 2.5 2.0 1.9 1.9
7.5 1.5 1.3 1.8 1.9 1.9 1.9
..
Numbera after Hours:12 15 19 22 30 1 8 1.7 2.1 1.6 i:s i:9 4.4 1.8 2.1 2.0 9.9 17.1 2:1 .. 515 16.9 2.0 .. 5.4 16.6 1.9 .. 2.2 3:5 7.0 5.0 9.5 15:2 3:5 7.0 16.0 33:O 10.2 25.0 . . 13.7 17.5 17.6 19.6
.. .. ..
.. ..
..
i.8 1.8 2.2 2.5 2.3 3.2 2.3 810 0 Milligrams of KOH per 2.1 8.7 2.2 9.5 gram of oil needed for neu2.5 13.0 tralization. 2.3 14.0 5.0 12.4 8.0
.. .. ..
VOL. 31. NO. 9
that the material was largely carried out of the tube by the stream of oxygen bubbles. The current of oxygen passing through the castor oil a t this elevated temperature greatly accelerates oxidation. Thus, in a few hours the untreated castor oil can be oxidized to as great a degree as it is by a year of storage.
Effect of Addition Agents The results of this study of antioxidants for castor oil are shown in Table I and Figure 3. The table is arranged in the order of decreasing effectiveness of the compounds as antioxidants for castor oil. Figure 3 shows that a considerable number of these compounds act as pro-oxidants instead of antioxidants. The data bear out the conclusion of Mattill that if there are two hydroxyl groups in the ortho or para position, the antioxygenic activity is high and the meta compound is inactive. This conclusion is shown by the fact that hydroquinone and catechol are strong antioxidants and their meta isomer, resorcinol, is a weak pro-oxidant.
25
20
cc 15
5 z
:
10
T
5
1. 2. 3. 4. 5. 6. 7.
Control p-Thiooreeol Thio-&naphthol m-Cresol +Nitrophenol Thymol p-Cresol
I
I
I
8. o-Cresol 9. p-Nitrophenol Resoroinol Benzvl aloohol Glyol'ne Diamylamine Diphenyl sulfide
10. 11. 12. 13. 14.
15. 16. 17. 18. 19. 20. 21.
Phenyl-a-naphthylamine Morpholine a-Naphthol 8-Hydroxvlauinoline Catechol Hydroquinone Pyrogallol
All three cresols are mild pro-oxidants but the meta isomer is stronger than the ortho or para. o-Nitrophenol is a slightly stronger pro-oxidant than p-nitrophenol. Benzyl alcohol is a weaker pro-oxidant than the other three isomers, the cresols.
Literature Cited (1) Kirk, P.L., Craig, R., and Rosenfels, R. S., IND. ENQ.CHEM. Anal. Ed., 6, 154-5 (1934). (2) Mattill, H. A., J. Biol. Chem., 90,141-51 (1931). (3) Tanaka, Y.,and Nakamura, M., J. SOC.Chem. I n d . J a p a n , 33, Suppl. Binding 107-9, 126-30 (1930); 34,Suppl. Binding 405-6 (1931); 35, Suppl. Binding 81-2 (1932); 36, Suppl. Binding 286-92, 335-7, 408-10 (1933). (4) Yamaguchi, B.,Rept. Aeronaut. Research Inst. Tokyo Imp. Univ., 5, 195-229 (1930). RE&BAS&f o r publioation b y the Chief of Ordnanoe, United States Army. Statements and opinions are t o be understood as individual expressions of their author, and not those of the Ordnanoe Department.
