Gum Formation in Gasoline I.
Measurement of Gum Stability of Gasoline
T. H. ROGERS, J. L. BUSIES,
AND
P. T. WARD,Standard Oil Company (Indiana), Whiting, Ind.
GUMCOKTEXT The increasing use of lapor-phase gasoline, in recognized that cracked response to the demand .for motor fuels of better As stressed b y W a g n e r and g a s o l i n e s are unstable H y m a n ( I C ) , the varnish-like knock rating, has intensified the problem of satisand form gum upon aging in oil-insoluble material obtained gum stability of gasoline. factorily ecaluating the t h e p r e s e n c e of a i r , T h e by e v a p o r a t i n g a sample of I t is shown that the Voorhees oxidation test, cracking developments of the oxidized g a s o l i n e represents a which measures the oxidafion beharior of gasopast few years h a v e s e r v e d polymerized product from unto emphasize the importance line at 100" C. in terms qf fhe induction period, stable o x i d i z e d substances in of this question, since the trend the gasoline. This end product has certain adcanfages ocer fhe metal bomb test. is not only toward production is u n i v e r s a l l y called "gum," gum Results correlating the Voorhees test with of more highly c r a c k e d a n d and, although it is known that storage tests in glass ut 35' C. are shoun, and a hence less stable gasolines, but gum is not present as such in fentative relationship between this standard also toward a higher percentage the gasoline, it is conventional to of c r a c k e d n a p h t h a in the storage test and practical siorage is indicated. refer t o an o x i d i z e d g a s o l i n e marketed gasoline. as containing gum; the residue Expressed in terms of the time required to f o r m S'oorhees and E i s i n g e r (14) o b t a i n e d upon evaporation is 10 mg. of g u m per 100 cc. by A . S. T . 1 1 . .Vethod showed that gum deposition in known as the gum content of A , which is deemed to be the m a x i m u m amount the internal combustion engine the gasoline. It was found by permissible ,for satisfactory sertice, a n induciiori is due to gum resulting from a Brooks (7) a n d o t h e r s t h a t previous oxidation of the gasoperiod of 400 minutes corresponds to approxiperoxides a r e i n t e r m e d i a t e line. To measure the stability compounds in the oxidation of mately a year of storage life in vented iron barrels of the gasoline, an accelerated cracked gasoline, and Yule and at atmospheric temperature (Chicago region). oxidation test was p r o p o s e d , Wilson (16) have s h o w n that While the caidence is that in quiet storage in in which the gasoline is agitated the g u m content c o r r e l a t e s large tanks the rate of solution of oxygen in the in a closed f l a s k in the presw i t h the peroxide number of e n c e of o x y g e n a t 100" C. gasoline is largely the determining factor, it apaged gasolines, indicating that (212" F.), and the amount of gum f o r m a t i o n t a k e s place pears that Ihe protection afforded by low oxygen oxygen absorbed is measured. m a i n l y by polymerization of supply is not a practical insurance against gum It w a s a l s o s h o w n t h a t a peroxides. Consequently, the trouble. small amount of gurn in gasoconditions of evaporation (temline a t the time of use will cause oerature. rate. etc.) will affect no appreciable harm, and various experiments were carried the amount of residue obtajned from a given'sample (11, out to discover how high a gum content is permissible. 12). It appears (6,6) that the results obtained by the Similar results have been obtained by Hoffert and Claxton various evaporation methods proposed bear a fairly constant (4) in studying the resin formation of motor benzene. relation to one another, so that such considerations as conThe work of Hunn, Fischer, and Blackwood (10) served to venience and reproducibility are the deciding factors in a confirm the general conclusions already preserited and to choice of method. Very satisfactory results by the 100" C. introduce the air jet method for determining gum content air jet method have been obtained, and all results on gun1 and the metal bomb test for stability. This latter test has content reported herein are by that method (Method A, 3 ) . been used rather widely in the industry, although no adeThe work of Voorhees and Eisinger tentatively indicated quate correlation of the results with aging has been published a gum content of 10 mg. per 100 cc. by the steam oven (8). Ramsay (13) has determined the effect of oxygen pres- method a t 162" C. as the limiting proportion for satisfactory sure and of temperature on the induction period, drawing performance in an engine. This corresponds to approxithe conclusion that the induction period should be deter- mately 20 mg. per 100 cc. by A. S. T. ill. Method A ( 3 ) . mined a t two or three temperatures in order to predict stor- More recent work, as covered in the A. S. T. M. report, inage stability. Similar conclusions were arrived a t by Aldrich dicates a lower limit. A recent test, supervised by the Engine and Robie ( I ) , who made a comprehensive series of tests of Laboratory staff of this laboratory, may be cited, in which induction period a t temperatures ranging from 80" to 120' C. the gum content of the gasoline was the result of normal aging. Of the gasolines giving irregular slopes, some contained con- This test was run in a hlodel A Ford engine; before the test siderable amounts of gum when tested, and it would appear run was started, the valves and head of the engine and the that an induction period test could not be expected t o have carburetor were carefully cleaned and a new intake manifold significance. Presumably these gasolines had already passed was installed. The test gasoline was obtained as a result of a the "break" point, and the results obtained by an accelerated storage test in a 6000-gallon tank, and frequent tests had test would be largely a function of the method employed. shown that the gum content was increasing very slowly, The major gum problems confronting the gasoline manu- averaging 18 mg. by Method A. facturer are (1) the development of a sound method for The car was in routine mail service and the first 1600 predicting stability and ( 2 ) the finding of suitable means of miles were run during the period April 2 to May 10, 1932, attaining the desired stability cheaply and satisfactorily. with a consumption of 104 gallons of gasoline. On May 10 This paper deals chiefly with the first of these two problems. the head, valves, intake manifold, and carburetor system
OR some time it has been
' F
,
397
Vol. 25, No. 4
398
c
1
2
A
4
B
3
3
F1m;~ti1. 'l'es~OF GUM ' ~ ~ L E H A N C P : IN Fox" CAR 1.
valves 2 and 3 nfter 1650 milee;
8.
Valves 2 sad 3 after 3087 miles: C.
were carefully examined. The carhiiretor showed evidences of gum a t the flanges and fittings, where gasoline had leaked. The butterfly valve was tarnished and had a sticky surface. The rear a n n of the intake manifold had a slight layer of "varnish," the front arm m s normal, and SOIIIC deposit had built up on the vertical riser. Inlet valves and ports 1 and 2 were normal, whereas the two rear inlet valves and ports had irregular deposits, as much as '/a inch thick in places. The engine was reassembled without removing any of the gum deposits, and the test continued until June 17, at wliielr time the total test mileage N ~ S3057 and the total gasoline consumption was 19.3 gallons. Following are the observations: Carburetor: 1. More pronounced superficialevidences ai gum. 2. Butterfly valve had thin coating over entire surface, but did not stick a t any point in operation. Intake manifold: 1. Not much ohenge in rear arm sinoe previous observation; front normal. 2. Deposit in riser increased somewhat, now about 1 mm. (0.04 inch) thick. ports: Ports 1 and 2 showed no sppreciable change. The deposita in ports 3 and 4 had increased, some lumps being about aheinch thick.
st the two examinations. The combustion chamber was normal a t both examinations. 'This test is continuing and no operating difficultieshave been
Valves 1 and 4 after 3087 miles
experienced; no appreciable change in performance has been noted after XI00 miles, in spite of the marked evidences of gum deposition noted above. The gasoline was run for gnm content frequently during the 3000-mile test period, and a plot of the results showed that gum had increased during the test from 16.5 mg. to 19.5 mg. per 100 cc., thus averaging 18.0 mg. for the test. Nearly all previous tests on gum tolerance have involved the use of a synthetio gasoline, generally made by blending a sample of high gum content with a stable gasoline of zero gum content. The present test on unstable gasoline containing naturally formed gum shows appreciably greater evidences of gum deposition than might he expected from previous tests, and it appears that an effect on the performance of the car is only a question of time, Considering all the data, it is felt that a gum content of 10 mg. per 100 cc. by Method A represents a reasonable upper limit for satisfactory gasoline. I n the present paper, therefore, the results of aging tests are expressed in terms of the time required to form 10 mg. of gum, which period is called, for brevity, the "storage life." STABILITY
TEST
Voorhees and Eisinger ( I ) described two methods of making an accelerated oxidation test on gasoline. The first involved determination of the oxygen absorbed and the second involved heating the gasoline for a fixed length of time (5 hours) and determining the amount of gum formed. Further experience has shown that the first method is much to be preferred. It gives complete information regarding the oxidation characteristics of the gasoline, whereas the second gives only one point on the unrve
April, 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
The apparatus used in this work is shown in Figure 2. The flasks are carefully cleaned with chromic acid solution and dried. A current of oxygen is passed into the flask, through a delivery tube reaching to the bottom, for several minutes; 100 cc. of the test gasoline are uickly poured into the flask, which is then tightly connected to &e manometer system by means of a rubber stopper, securely tied. No difficulty has been experienced with oxidation of the stoppers as reported by Herthel and Apgar (9). The stoppers are carefully washed and frequently renewed. The flask thus sealed at room temperature is placed in
n
399
this, the temperature lag in the metal bomb test may be as long as an hour, thus requiring a correction of 45 to. 50 minutes (1, IS). This correction is often a large proportion of the total time of the test, and obvious1 the amount of this correction is to a large extent a function of t i e mechanical features of the bomb and the bath. (2) Pressure is measured by a mercury manometer and considerably greater accuracy is attained. With the apparatus described, the amount of oxygen absorbed is measured with an accuracy of about 2 cc.; in the metal bomb the lack of precision of the gage apparently does not permit a quantitative measure of the oxygen absorbed. SIGNIFICANCE OF STABILITY TEST. Aside from the quantitative correlation of the induction period with storage, which will be covered in a later section, some data indicating the basic soundness of the results of the stability test are as follows : (1) Figure 3 shows the results of the stability test on various kinds of cracked gasoline. The induction periods of these gas+ lines are: GASOLINE
IKDCCTION PERIOD Minutes 130 390
Vapor-phase raw Vapor-phase: acid-treated Cross-cracked, raw Liquid-phase, finished
EHTRIC 140 CYCLES PER HIN.
FIGURE 2. APPARATUS FOR VOORHEES STABILITY TEST
TIME-MIN
FIGURE 3. 1.
(1) Temperature equilibrium in the gasoline is established qmte rapidly by virtue of the shaking. Temperature readings have been taken during tests by supporting a thermometer in the gasoline. These showed that steam temperature is attained within 4 to 5 minutes after the steam is turned on; compared to
610
These results are in harmony with general observation as to the gum stability of these stocks, as well as rational in terms of our knowledge of the chemical constitution of the gasolines. (2) When a gasoline is aged, thus becoming progressively less stable, with gradual formation of gum, the induction period of the gasoline also decreases. Figure 4 shows the results of an aging test of a sample of vapor-phase gasoline. It will be observed that the induction period decreases regularly with aging. Thus the induction period, measured at successive intervals, properly indicates the decreasing stability of the gasoline, as evidenced by its increasing gum content.
position in the steam bath and attached to the shaking machine, after which the steam is admitted. The pressure rises rapidly, and after about 25 minutes constant readings are obtained on the manometer. The pressure then drops gradually, depending on the stability of the gasoline. After a more or less extended period, the rate of ox gen absorption becomes increasingly rapid, finally attaining an a&ost linear rate which does not var appreciably with the different gasolines studied. Pressure reaings are taken from time to time and, by subtraction from the initial constant value, the volume of oxygen absorbed is computed. Obviously, the accuracy of the readings for pressure drop depend on the maintenance of uniform room temperature and steady barometric pressure. It is ordinarily not necessary to make corrections for changes in barometric pressure. The induction period is defined as the time from the start of the test (allowing 5 minutes after the steam is turned on, for temperature lag) till the rate of oxygen absorption becomes one cc. (standard conditions) per minute. This is, of course, an arbitrary definition; experience has shown that it is a satisfactory and significant measure of the stability of the gasoline. It is well established that gasoline absorbs oxygen, with subsequent gum formation, during this induction period; the rate at which this oxidation takes place varies with the gasoline, and obviously the slope of this line is of some significance. Therefore, record is also kept of the amount of oxygen absorbed a t the induction point. Obviously, for two gasolines having the same induction period, the one with the smaller amount of oxygen absorbed at that point is the better. The Voorhees stability test has two marked advantages over the metal bomb test:
320
2.
VOORHEES OXIDATION STABILITY TEST
Vapor-phase raw Vapor-phase: acid-treated
3. 4.
Cross-cracked raw Liquid-phase. 'finished
(3) The effect of inhibitors is to increase the induction period in proportion to the amount used. As covered in the accompanying article, the increase in induction period is a linear function of the concentration of inhibitor. These results are in general accord with those obtained b Alyea and Bkckstrom (9)in studying the effect of inhibitors on t i e oxidation of sodium sulfite.' While this does not furnish absolute proof of the correctness of the induction period test, it is an interesting indication of its soundness.
CORRELATION OF INDUCTION PERIOD WITH STORAGE BEHAVIOR OF GASOLINES The conditions of practical storage vary so widely that a n experimental study of the aging of gasoline presents a number of difficulties. Temperature variations, the presence of different metals and other possible catalytic influences, the presence of water, and the rate of air supply are all factors of more or less importance. Considering the com1 Strictly, Alyea's results showed t h a t t h e r a t e of oxidation is inversely proportional t o the inhibitor concentration plus a constant, b u t over most of the concentration range the velocity was practically proportional to the concentration.
I N DUSTR IA L A N D E S GI SEE R I N G C HE M IST R Y
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Vol. 25, 210. 4
TABLE I. DATAON BARREL STORAGE OF GASOLINES STORAGE IN BARRELS Storage life Weeks
IXITI4L
DESIGNATION 3 4
GA~OLIXE
IXDIXTIOS PERIOD
Av. temp.
Vapor-phase, sweetened No. 3 a-naDhthol No. 3 p-bexkylaminophenol No.3 p-bensylaminophenol 50% vapor-phase 50% commercial ethylired gasoline Vapor-phase, raw
+ + +
5
No. 1
2B.U
+
+ 0.001% p-bensylaminophenol
Cross-cracked, raw
No. S
STOR.AQE LIFE In bottles" Ratio Weeks
+ 0.0005% p-benaylaminophenol
49
3 1.5
..
(9.4)
320
41
(5)
490
49
(9.4)
2.4
25d
31
At 95' F. (35' C.). 6 c d Separate barrels of the same stock. e 3 mg. formed in 36 weeks.
..
0
I
I
plication of these factors, as well as such obstacles as the length of time and the outlay of materials involved, it is not surprising that the data reported have been very meager. TESTSIN GLASBBOTTLESIN PRESENCE OF OXYGEN. I n order to eliminate all variables except temperature, a "standard" storage test in glass bottles has been used extensively. The first group of tests to be described consisted in the storage of samples in half-gallon (1.9-liter) bottles a t 35' C. (95' F.) in the presence of oxygen. Several identical samples of each of the gasolines were prepared, filling the bottles half full in an atmosphere of oxygen and then sealing the bottles. These bottles were stored in an artificially lighted room at 35" C., and a single bottle was taken from time t o time for test. The gasolines used represented a mildly acid-treated
STORPGE T I M E - N E E K S
OF GASOLINE AGINGTEST FIGURE4. RESULTS
[Treated cracked gasoline i n storage a t 35' C. (95' F.) in air] 0 Induction period X Gum content
vapor-phase gasoline and blends of this gasoline with a much more stable commercial gasoline. The storage period was of such duration that in every case the gum content values reached 50 or 60 mg.; tests were also made for induction period and antiknock value on each sample. The general trend of the results for gum content and induction period were such as are indicated in Figure 4. It was found that a t any given time an induction period of under 100 minutes is indicative of very low stability. Values as low as 50 on a stored sample are indicative of an appreciable gum content, and it should be pointed out that the nature of the test is such that 30 or 40 minutes are minimum inductionperiod values, indicative of gum contents far beyond the critical range. It has been previously pointed out that aging of unstable gasoline results in loss of antiknock value as well as gum formation, although the relation between the two types of deterioration has seemed rather uncertain. All of the storage tests of this group showed definitely that no appreciable loss of antiknock value occurred until serious oxidation, with formation of over 15 mg. of gum, had taken place. Beyond this point there was no consistent relation between the amount of gum and the extent of loss of knock rating. Some samples lost as much as 3 octane numbers when the gum content reached 25 mg.; others showed less change in knock rating, dropping only 2 octane numbers with a gum content
of 40 or 50 mg. Altogether, however, this is unimportant as a practical question, since the results yield the conclusion that gum trouble would be encountered long before the knock rating of a gasoline is appreciably affected by oxidation. Figure 5 shows a plot of initial induction period against the time required t o form 10 mg. of gum (i. e., storage life), the latter value being obtained from a smooth curve of gum content us. time of storage. A straight line fairly expresses this relationship, indicating that the storage life is a linear function of the induction period. Some discrepancies are noted, but these are well within the experimental results for gum content obtained with different bottles. The gasolines in this Peries are all closely related, inasmuch as they all represent blends of two basic stocks. Samples 1 and 2 are vapor-phase gasolines of different end points; 3 is sample 1 ethylized; samples 4, 6, 8, 9, and 11 are blends in amounts of 10 to 50 per cent of vapor-phase gasolines 1 and 2 in relatively stable commercial gasoline; samples 5 , 7 , and 10 are similar blends ethylized. TESTS IN GLASSBOTTLESIN PRESEXCE OF AIR. The procedure of sealing the bottles and using a separate bottle for each test period, as described above, was adopted mainly to avoid loss of light ends and thus provide reliable data on knock rating. It was observed, however, that two samples, prepared carefully in the same manner, may differ in rate of gum formation, thus causing gross irregularities in
?
01
c
_/;3
FIGURE5. RELATIONBETWEEN STORAGE PERIODIN ATMOSLIFE AND INDUCTION PHERE OF OXYGEN [Storage in bottles a t 35' C. (95' F.)]
the gum content-time curve. It appears to be impossible to eliminate entirely these irregularities, although some improvement was obtained subsequently by washing and drying the bottles more carefully. I n order t o average out these irregularities in later work, several bottles of the same sample were kept under test) and a composite from these was made a t intervals for test. Having shown that serious gum formation precedes significant loss of antiknock, less attention was paid to the latter. The second group of tests, involving several series of samples, was carried through with the altered procedure, eliminating the use of oxygen. The samples were exposed to air initially to insure saturation and were opened frequently
April, 1933
I IC'D U S T R I A L A 3. D E S G I N E E R I N G C H E M I S T R Y
1 01
In these tests the barrels were Vented to allow a normal supply of air above the gasoline. Several experiments were made t o determine whether the rate of gum formation in barrels is limited by the rate of solution of oxygen. In one GaSOLIXE IKDCCTIOSPERIOD test a barrel containing gasoline which had already formed Mi7tutes ii mg. of gum was blown with air periodically. This did not 1:35 1. Vanor-phase. raw 3 15 2. Nd. 1 + 0.001% o-benavlaminoohenol .~ appreciably alter its rate of gum formation. Other coni1:30 3. Vapor-phase sGeetened" 2130 4. No. 3 + 0.0635% a-naphthol parative tests indicate that the air supply is not a limiting 270 5. No. 3 + 0.0015,7, p-benaylaminophenol factor in barrels, and this is confirmed by calculations on 380 6. Vapor-phase acid-treated s LO 7. h-o. 6 + 0 .0025% a-naphthol the rate of solution of oxygen in gasoline. 320 8 . Cross-cracked raw 400 9. KO.S + O.OOd5a p-benzylaminuphenol TESTSIN HORIZOlVT-4L TASKS. Aging tests on two gasolines have been made in 6000-gallon horizontal tanks. These The gasolines included in Figure 6 coI-er a wide variety, \\-ere the same as gasolines 3 and 4 shown in Figure 6. Figure involving differences in cracking conditions, anti degree of 7 shows the storage results for the unstabilized gasoline, refinement, as well as the use of two different antioxidants. including the data on barrel storage for comparison. The The data do not fall on a single curve but form a relatively rate of gum formation in the tank is practically linear, as far as the test has gone, and it is much slower than in the -1 barrel a t the same temperature. Gasoline 4 (stabilized .ample) contains only 6 mg. of gum after 60 weeks. Although these tanks are vented to allow breathing, it is apparent that oxidation is limited by lack of oxygen; the explanation is that the rate of solution of oxygen in the gasoline is less than the potential rate of consumption. The lines leading upward from the main curve show the behavior of 2 9 5 2 20 these stocks when samples are taken from the tanks and II stored in smaller containers in the presence of air a t atmosc o4 2 c3 pheric temperature. /.* c: The behavior of the removed samples is rather erratic, 0 200 400 600 0 00 but in every case gum formation is markedly accelerated imI N IT'A. I hDUCT ! O N PER IOD-M IN. mediately after removal of the sample from the tank. Also FIGURE 6. R E L ~ T I OBETREEN N S T O R 4 G E [LIFE the rates of gum formation of the successive samples become AND INDUCTION PERIOD OF GASOLINES IN ~ I R increasingly greater as the stock is more aged, and it appears [Storage in bottles a t 35' C (95' F ) I that for some reason the gasoline, whose rate of gum formation wide band, and iiiterebtiiig relationships between the nature of has previously been decreased for lack of oxygen, forms gum a t the sample and its position on the plot are seen. Tentatively, an abnormal rate when exposed to normal air. This latter, it appears that the f'olloming generalizations are justified : of course, applies to the case where the gasoline has already Raw gasolines fall below this average line, showing that their passed the induction period. rate of gum formation is faster than would be expected from the inductioii period. Acid-treated gasolines have a slower rate than would be predicted, whereas the untreated sweetened gasolines fall on or close to the average line. Gasolines stabilized by a-naphthol show a more rapid rate than is indicated by induction period, whereas those stabilized by p-benzylaminophenol (an efficient antioxidant) fall on the same line as the parent gasoline. Another set of tests with the same samples was run in 2-gallon (7.6-liter) cans in the presence of air a t approximately the same storage temperature as the preceding. The results were somewhat more irregular than the bottle tests, but on the whole did not indicate an appreciably different rate of gum formation. FIGURE 7. GUM FORM4TION OF CRACKED GASOTESTSIN IROK BARRELS.Some of the gasolines of the LINE I N 6000-GALLON TANK preceding group were stored in clean iron barrels a t at(130-minute induction period) mospheric temperature. These did not yield ratisfactory data in some cases. The characteristic behavior mas a slower Calculations indicate that the rate of solution of oxygen rate of gum formation than in bottles, but some of the in gasoline in large tanks will be far below the potential barrels showed an abnormally accelerated rate after some consumption for even a moderately stable gasoline. Thus gum was formed, indicating the presence of a catalytic mate- the rate of gum formation, as long as the gasoline is undisrial. Tests in progress a t this time show evidence of greater turbed in the tank, will be a function of the oxygen supply regularity, presumably because of greater care in cleaning the rather than the stability. However, upon exposure to air, barrels. Table I shows results obtained to date, several of an unstable gasoline would undoubtedly show a rapid rate of the tests not being yet complete. gum formation. In general, the rate of gum formation in barrels a t atmospheric temperature is roughly one-half that in bottles a t DISCUSSION OF RESULTS 95" F. (35" C.). The irregularity of the data does not justify any more than a tentative comparison as yet, but it Altogether, the correlated data show that the Voorhees seems that the rate of gum formation in barrels a t 50' F. stability test is a sound method for predicting the storage (10' C.) is considerably more rapid than would he expected behavior of gasoline. An induction period of 390 minutes theoretically from the results a t 95" F. corresponds to about 6 months of storage life in the 35" C.
enough to avoid depletion of the oxygen content. Figure 6 shows the relation between initial induction period and storage life, the samples being as follows:
~
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INDUSTRIAL AND ENGINEERING CHEMISTRY
402
bottle test or to a year (and perhaps longer) of storage life
at atmospheric temperature when the gasoline is saturated with normal oxygen. The irregularity of the conditions imposed in practical storage are such that a factor of safety, as regards stability, must be used by the refiner; the discrepancies found in the induction period-storage life relationship are within a reasonable factor of safety. As indicated by storage tests in tanks, and further coniirmed by calculations on the rate of solution of oxygen, it appears that the diminished oxygen supply will provide a factor of safety of some consequence, as far as quiet storage in large tanks is concerned. However, it should not be overlooked that the stability of gasoline is constantly being decreased under such conditions; with the possibilities of oxidation under the more severe conditions of subsequent storage, it appears that the only safe course is to make gasoline sufficiently stable to resist oxidation for the storage period, assuming a normal air supply.
LITERATURE CITED
Vol. 25, No. 4
(3) Am. Soc. Testing Materials, Rept. of Corn. D-2, Appendix, 1932. (4) Benzole Research Committee, 6th Rept., 1929, 10. (5) Bridgeman and Adrich, S. A . E. Journal, 28, 472 (1931). (6) Bridgeman and Molitor. Paper presented at 9. A. E. Meeting, June 12 to 17, 1932. (7) Brooks, ISD.ENO.CHEM.,18, 1198 (1926). (8) Flood, Hladky, and Edgar. Paper presented before Division of Petroleum Chemistry a t 80th Meeting of American Chemical Society, Cincinnati, Ohio, September 8 to 12, 1930. (9) Herthel and Apgar, Am. Petroleum Inst., Proc. 10th Ann. Meeting, 11, KO.1, Sect. 111, 124 (1930). (10) Hunn, Fischer, and Blackwood, S. A. E. Journal, 26, 31 (1930). (11) Littlejohn, Thomas, and Thompson, J . Inst. Petroleum Inst., 16, 684 (1930). (12) X’orris and Thole, Ibid., 15, 681 (1929). (13) Ramsay, IND.ENO.CHEM.,24, 539 (1932). (14) Voorhees and Eisinger, Am. Petroleum Inst. Bull., 10, 169 (1929); S. A . E. Journal, 24, 584 (1929). (15) Wagner and Hyman, Am. Petroleum Inst., Proc. 10th Ann. Meeting, 11, No. 1, Sect. 111, 118-23 (1930). (16) Yule and Wilson, IND.ENQ.CHEM.,23, 1254 (1931). RECEIVED September 20, 1832. Presented before the Division of Petroleum Chemistry a t the 84th Meeting of the American Chemical Society, Denver, Colo., August 22 to 26, 1932.
(1) Aldrich and Robie, S. A . E. Journal, 30, 198 (1932). (2) Alyea and BAckstrom, J . Am. Chem. Soc., 51, 90 (1929).
Vitamin A Content of Naturally Colored Nut Margarines CHARLESF. POEAND HAZELA. FEHLMANN, University of Colorado, Boulder, Colo.
The vitamin A content of a number of naturally colored nut margarines is determined. The amount of vitam,in A in these products is found to be low when compared with butter.
U
NDER a decision dated Xovember 12,1930, the Bureau of Internal Revenue ruled that unbleached palm oil might be used as one of the substantial ingredients of oleomargarine. Many manufacturers, thereupon, started to make products containing varying amounts of palm oil. However, a law was later passed imposing a tax of 10 cents per pound on all naturally colored oleomargarines. The object of the investigation reported in this paper was to determine the vitamin A content’ of a number of nut margarines colored by the addition of palm oil. The methods and procedures used were essentially those outlined by Sherman and Munsell (7) and Sherman and Burtis (6). Male albino rats, 28 days of age and averaging about 50 grams in weight, were used. These were fed, up to the time of weaning, the “colony diet” recommended by the Vitamin Assay Committee of the American Drug Manufacturers’ Association ( 3 ) . A period of about 4 weeks was required to deplete the body store of vitamin A. The diet used for this depletion period consisted of the following: % Casein (vitamin A-free) Irradiated yeast, dried Agar-agar, fine
18 7 2
% Corn starch Salt mixture, Osborne and Mendel ( 5 )
69 4
When the depletion period was ended, different levels of the nut margarines were added to the basal diet, and the experiment continued for 8 weeks or until death. Enough vitamin-free cottonseed oil was fed to each animal t o make the total fat constituent of the diet one gram per day. Negative controls were run on a representative number of animals. To the diet of a number of animals which were used as positive controls, were added different daily levels of butter. 1 Vitamin A as used in this paper refers to vitamin A per se as well as to oarotene, the precursor of this vitamin
The records of the growth of the animals which were fed the different samples of margarine are listed in Figure 1. Samples from eight different manufacturers were examined, and are indicated by numbers. Sample 5 was later found to contain animal fat, cottonseed oil, and soy-bean oil. The controls are shown in Figure 2. Considerable variation was noted in the vitamin content of the different samples. The Sherman vitamin units per gram were calculated, and ran from 0.65 for sample 6 to 4.7 for sample 8 (Table 11). It was thought that some of the growth might be due to the vitamin A in the added milk. Each sample was submitted to a chemical analysis in order to determine the amount of pure fat present. These chemical results are given in Table I. Some of the fat from each sample was freed from the salt, water nd curd. An amount approximately equivalent to the el required to produce an average gain of 3 grams per week was fed to a second series of rats. The average growth curves for these animals were practically identical with those of the animals receiving equivalent amounts of the original sample; this showed the vitamin A content to be derived from the fat rather than the added milk.
2
TABLEI. SAMPLE
CHEMICAL
hIOISIURE
ANALYSISO F
F ~ T
CURD
MARQARINE SAMPLES SALT-FREE ASH SALT ASH
%
%
%
%
%
%
20.52 8.55 15.32 17.00 6.11 11.10 9.12 8.24
74.46 86.59 79.72 77.25 90.45 84.97 86.12 88.21
1.57 1.42 1.30 1.96
3.47 3.44 3.66 3.79 1.84 2.32 3.02 2.42
3.31 3.24 3.25 3.48 1.70 2.11 2.78 2.28
0.16 0.20 0.41 0.31 0.14 0.21 0.24 0.14
1.60
1.01 1.74 1.13
The manufacturer of each of the nut margarines was consulted as to the composition of his product. The results
