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542
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(4) Mardles and Moss, J . Inst. Petroleum Tech., 15,657, 673 (1929). and Eisinger, J . SOC. A~~omotiWE a , 24, 5@-92 d paper ~ presented ~ ~ before , ~ i of ~ (5) . Voorhees (1929). Petroleum Chem., 80th Meeting of Am. Chem. SOC.,Cincinnati, Ohio, September 8 t o 12, 1930. (2) Herthel and Apgar, Oil Gas J.,28, 136 (Deo. 5, 1929). RECEIVED August 24, 1931. Presented before t h e Division of Petroleum (3) Hunn, Fischer, and Blackwood, J. SOC.Automotive Eng., 25, Chemistry at t h e 82nd Meeting of t h e American Chemical Society, Buffalo,
LITERATURE CITED
(1) flood, ~ l ~ d and k ~ ~,
3 1 (1930).
N.Y., August
31 t o September 4, 1931.
Composition of Straight-Run Pennsylvania Gasoline 11. Fractionation and Knock Rating M. R. FENSKE, D. QUIGGLE,AKD C. 0. TONGBERG School of Chemistry and Physics, Pennsylvania State College, State College, Pa.
P
by the Ethyl Gasoline LaboraENKSYLVAKIA straightI n one fractionation, straight-run Pennsylvania tories. For some p u r p o s e s i t r u n g a s o l i n e h a s been gasoline was separated into fractions of alternate fractionated by means of may be better not to add lead high and low knock rating. It was found that to the sample being rated, but the 27-foot and 52-foot columns this variation in knock rating was due to straightrather to match its rating with described in a previous paper (3). chain parafins and to aromatic and naphthenic other s t a n d a r d i z e d fuels in It is hoped that the results obterms of octane number. Since tained will furnish fundamental hydrocarbons being concentrated in certain fracboth r a t i n g s are n e e d e d , this information on the composition tions. Refractionation enabled some substances point is discussed later in conof the gasoline and may be the to be obtained which closely approximated pure nection with Figure 6. means of i m p r o v i n g its antimaterials, both as to physical properties and knock qualities. FR.4CTIONATION OF 510" F. knock behavior. A n y one normal parafin is Two b a r r e l s of crude petroEXD-POINT GA~OLIXE leum were obtained from flooded present in the Pennsylz'ania straight-run gasoline Sine gallons of the 510" endwells on the Jones Lease, Rew to the extent of 2 to 5 per cent. It is very likely point gasoline were charged into C i t y , l o c a t e d about 5 miles that these normal para#ns, while not constituting the 2i'-foot, 3-inch d i a m e t e r south of Bradford and belonga very large percenlage of fhe gasoline, are largely column. A total condenser was ing t o t h e K e n d a l l Refining responsible for the knock. The fractionating used, a n d t h e f r a c t i o n a t i o n Company of Bradford, Pa. This carried out a t about 20-30 to 1 crude oil was b a i l e d out of a equipment used, effectively concentrated these reflux ratio (liters of reflux to run tank, placed in clean drums, parafins and permitted their removal from the liters of product). The remains e a l e d , a n d s h i p p e d to the gasoline. der of the operating details have l a b o r a t o r y . T h e c r u d e oil been described previously ( 3 ) . was towed bv a simde batch distil1at:on in "order to obtain the gasoline. A considerable Complete data on this fractionation are &own in Figure 1. amount of low-boiling material came off of the crude a t the The distillation ranges of the charge, distillate, and blended beginning of the distillation. This was condensed by means samples are also indicated. The boiling point (at about 737 of Dry-Ice in a container capable of withstanding pressure. mm. pressure), specific gravity, (diO,), refractive index, These light ends were not investigated, since they were known (n':), and knock rating (cubic centimeters of tetraethylto consist of propane, butane, and pentane. The distillation lead) are plotted against the percentage of total charge was carried on into the kerosene to ensure the removal of all distilled over. I n the rectification, 165 fractions were the gasoline from the crude. This distillate, comprising 39 collected, but knock tests were made on only 35 samples. per cent of the crude, is called, for the purposes of identifica- The fractions indicated by horizontal lines on the knock curve were blended, and the resulting samples tested as a whole in tion, 'L5100F. end-point gasoline." order to reduce the number of knock tests required. METHODOF RATINGKNOCK I n Figure 1 the first 5 per cent represents propane and The knock ratings were obtained on a Delco-Light knock- butane, principally, and some pentane which were condensed testing engine which had been used by the Ethyl Gasoline by means of Dry-Ice. These light ends are, of course, very Corporation prior to the Series 30 model. This engine was valuable, since their knock rating is zero or better. procured through the cooperation of Graham Edgar. All The plot shows clearly in which fractions of the gasoline the knock tests are referred to Ethyl Standard, 74 octane number. knock is greatest, and that there are alternately good and The rating indicates the number of cubic centimeters of bad fractions. It is of particular interest to note that the tetraethyllead (not Ethyl fluid) required to make a given curves of refractive index and density are the reverse of the fraction or gasoline equal to Ethyl Standard. I n some in- knock curve. I n each of the peaks of the density or refractivestances, fractions are better than Ethyl Standard. I n such index curves are concentrated the aromatic hydrocarbons of cases they are given as negative ratings, and lead is added to that particular boiling point. The valleys do not contain any the Ethyl Standard to equal the fraction being tested. The aromatics. Obviously then, since the aromatic hydrocarbons test procedure followed was the bouncing-pin method used do not knock, the peaks in which they are concentrated will be
hIay, 1932
I N D U S T R I A L A IV D E N G I S E E R I N G C H E h9 I S T K Y
of high antiknock value. The aromatic content of the peaks varies from 10 to 40 per cent, the remainder being naphthenes and branched paraffins. Each valley of the density or refractive index curve coincides in boiling point with one of the normal paraffin hydrocarbons-heptane, octane, decane, or hendecane. The isolation of various hydrocarbons of reasonable purity will be presented in a later paper. The rise and fall of knock rating with increasing boiling point is in disagreement with previously reported data ( 2 , 4), in which the knock increased uniformly with boiling point. However, the discrepancy is easily explained in view of the fact that this effective fractionation has successively concentrated paraffin, aromatic, and naphthene hydrocarbons. Clearly, to make an antiknock gasoline, the Clo and Cll fractions are to be avoided. This material is 18 per cent of the distillate, excluding the light ends, and its removal from the gasoline lowers the knock rating from 5.9 to 3.4 cc. of tetraethyllead per gallon. If all the fractions, excluding the light ends, with a knock rating below 7.6 are blended, a gasoline representing 62.8 per cent of the distillate is obtained with a knock rating of 2.0. COMPARISON O F SIMPLE DISTILLATION WITH FliACTIONATION. If, in contrast to fractionation, the same gasoline is separated into three equal volume cuts by a simple distillation, the following results are obtained: FRACTION (33% O F
GAGOLINE)
543
charge should give better separation, there being more of any one component present. In other words the peaks of the refractive-index and gravity curves should be higher and the valleys lower. The results of this fractionation are given in Table I. The peaks are actually higher and the valleys lower than in the first fractionation. Similar results were obtained by Hill, Henderson, and Ferris ( 5 ) ; for comparison some of their data are included. The distillation was extended to include part of the kerosene fractions to determine whether or not the refractive-index and gravity curves still had peaks and valleys. Table I shows that they had, as far as this fractionation was carriednamely, to i n c l u d e f r a c t i o n s as high as tetradecane. It was definitely established that the valleys c o n t a i n e d n o r m a l paraffins. n - H e x a n e , n-heptane, and n-octane of high purity were obtained simply by refractionation. By using chemical means of separation-namely, treatment with chlorosulfonic acid according to the method of Shepherd and Henne (7)-it was possible to isolate normal paraffins as high as tridecane. Fop example, subjecting a fraction located-in a valley, with a boiling point of 451" F. (233" C.) and a refractive index of 1.4392 (%'$), to chlorosulfonic acid treatment, gave, after 11 days, 38 per cent of a material with refractive index 1.4280 (n?). The limiting value appeared to be 1.4271, Extrapolation of a curve of Shepherd's (5)of refractive index against normal paraffin hydrocarbons ending a t dodecane, gives a value for tridecane of 1.4262 a t 20' C. The value in the International Critical Tables of 1.4419 a t 16.8" C. is certainly high. It is interesting to compare the results of this distillation with those reported by Brown and Carr ( 1 ) . They fractionated a quantity of straight-run gasoline from the Cabin Creek
KXOCKRATINQ Cc. tetraethyllead
1
2 3
1.25 6.8 9.1
These data indicate that the amount of material which must be removed to get a suitable gasoline is much less, the better the fractionation. Fractionation not only holds back the higher-boiling knocking fractions, but also concentrates the fractions largely responsible for the knock. FRACTIONATIOK OF %-GALLON CHARGE. I n order to check the previous results, as well as t o obtain more material for study, 25 gallons of the same 510" F. end-point gasoline were fractionated. Since the still held only 13 gallons, the gasoline was separated by simple distillation into three fractions of successive boiling ranges, and these were added to the still a t the proper boiling point. Unless the results on the first distillation gave the limits of separation, the use of a larger
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mmr
aF CM.QG~
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OF HEPTARE FRACTION FIGURE 2. RECTIFICATIOIS
Boiling range, 175" t o 225O F.
Field, W. Va. On their ninth fractionation they obtained a heptane fraction boiling a t 98.6" C. which was considered to be pure n-heptane. It had a refractive index of 1.4068 a t 20" C. Referring to Table I, the material with a boiling point of 95' C., where a minimum in the refractive-index curve occurs, is the fraction in which n-heptane is concentrated. The refractive index of this fraction is 1.3912 (n':). The value for pure n-heptane a t 20" C. is 1.3878 (8). Again, Brown and Carr reported pure n-octane, after ten fractionations, with a refractive index of 1.4059 (n?) and boiling point 124.3" C. Comparing these results with those given in Table I, the valley a t a boiling point of 124" C., in
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 24, No. 5
which n-octane is concentrated, has a refractive index of 1.4032 a t 20' C. The best value for n-octane at 20" C. is 1.3970 (6). These data indicate that this one fractionation of the 25-gallon charge is considerably better than the nine or ten fractionations reported by Brown and Cam.
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.
.
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RECTIFICATION OF A 175-225 ' F. FRACTION This material was obtained through the courtesy of the United Refining Company a t Warren, Pa. Its boiling range placed it between the benzene and toluene peaks on Figure 1, and it was this portion in which normal heptane would be present. Since the latter was known to knock badly, it was of particular interest to see what might result from a fractionation of this material. The results of fractionating 10 gallons are shown in Figure 2. The refractive index and boiling point are plotted against the volume distilled over. The refractive index furnishes a very convenient method of following the progress of a distillation, since it parallels changes in density, is subject to quick and accurate measurement, and undergoes a greater range of variation than the boiling point. It will be noticed that the benzene peak on the refractive-index curve follows after the hexane fractions, and a t the end of the distillation the refractive index is rising toward the toluene peak. The knock ratings of certain fractions from this distillation were measured. Whereas in Figure 1 the knock rating of the benzene peak is just about zero, it now has in Figure 2 a value of -8.7 cc. of tetraethyllead. That is, 8.7 cc. of tetraethyllead have to be added to Ethyl Standard to make it equal the knock rating of this fraction. These results certainly indicate better fractionation. Another fraction in the valley has a rating of $0.8 cc., and, with only two more liters of product taken off (out of 30 liters total), the knock rating rises to +8.8 cc. of tetraethyllead. It still has about the same value (9.0 cc.) after 4 more liters of product have been withdrawn. The highest knock rating on
F'
s
&4
8
I, t,
1
$'
9
FIGURE 3. RECTIFICATION OF 25-GALLON CHARGE OF 510' F. END-POINT GASOLINE
Figure 1 for this section is 6.6 cc. of tetraethyllead. Again these data indicate better separation. Finally, on the upward slope of the refractive-index curve the knock rating is +0.3 or very nearly equal to Ethyl Standard. It is of particular interest to note that the fraction boiling a t 207.5' F. (97.5' C.) has a knock rating of +9.0 cc. of tetraethyllead, while a fraction boiling a t 211.1' F. (99.5' C.) has one of only +0.3 cc. The results of this distillation substantiate those of the first distillation in every respect regarding the variation of knock with boiling point. Because separation is considerably better, the variation in the knock rating is more pronounced. The material responsible for this knock has been found to be n-heptane. It is not pure, however, but contaminated with methylcyclohexane. There is very little toluene in these fractions, as evidenced by the fact that no change occurs when
May, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
they are washed with concentrated sulfuric acid. The principal hydrocarbons in this 175225O F. fraction in the order of increasing boiling point are n-hexane, benzene, cyclohexane, isomeric branched heptanes, n-heptane, methylcyclohexane, and a very small amount of toluene. A complete discussion of these hydrocarbons will follow in a later paper. KNOCKRATINGOF 10 PER CENTBLENIIS I n order to obtain an idea of the knock ratings of the fractions from the 25-gallon distillation in concentrations approximating their occurrence in the gasoline, the rating was determined for 10 volume per cent blends of several fractions in a base gasoline. This base gasoline was Standard reference fuel B, of 67.5 octane number, which was obtained through the Standard Oil Company of 1450 New Jersey. W h i l e 10 I440 volume per cent was con,,,,; siderably greater than the ,,,,$ concentration of any one ~~~a~ hydrocarbon in the original gasoline, it was better zno to o b t a i n values for the P60 1390 lower per cent blends by I300 ?.Q40 amroximating from the 10 --
una^
b l e n d was u s e d , t h e amount of tetraethyllead urm D S ~ I L L o~ w required was too small for FIGURE 4. REDISTILLATION OF any degree of a c c u r a c y , HEPTANE-OCTANE FRACTION The method of rating the 10 per cent blends was still the number of cubic centimeters of tetraethyllead required to equal 74 octane number (Ethyl Standard). I n Figure 3 the approximate per cent of the various hydrocarbons found in the original gasoline is plotted against boiling point. Certain hydrocarbons are indicated which are known to be present in appreciable quantity. The knock ratings of several 10 per cent blends in Standard reference fuel B are also indicated. The latter data, together with the curve for approximate per cent present, will permit an estimation of the effect on the knock rating of any one fraction of the gasoline. Since the bad knocking fractions began above n-octane, blends were not made below this point. A comparison of these data with those of Figure 1 shows that the knock ratings of the fractions themselves parallel those of the 10 per cent blends. It should be remembered that this material was obtained from one fractionation of a gasoline of wide boiling range (510' F. end point). As shown by Figure 2 and other data which follow, these knock ratings do not represent the ultimate result obtainable in regard to the variations possible.
545
high for paraffins. There is no evidence of any significant quantity of olefins in this straight-run gasoline. The toluene peak has undergone considerable change in shape. It is seen that the 52-foot column has eliminated the toluene very sharply on the refractionation because the boiling point undergoes a rapid change a t this point, rising some 14" F. (8' C.). With this much of a difference in boiling point to work on, the 52-foot column functions perfectly. In contrast to the refractive index, the boiling point changes very gradually as n-octane is reached. This material is very complex, as it consists not only of branched octanes but also of cyclic or naphthene hydrocarbons. The column has, nevertheless, performed a satisfactory separation and has substantially freed the naphthenic material from the bad knocking noctane. One might believe from Figure 1 that there is an abnormal amount of moctane present because considerable tetraethyllead has to be added to a large fraction of material. However, this is not the case. The naphthenic material may have been freed from n-octane to the extent of 70 per cent or over, and yet the remaining, 30 per cent octane or less, for example, would have caused it to knock quite badly. In other words, a comparatively small amount of n-octane will give to a material a bad knock rating. While various hydrocarbons are indicated on Figure 4,they are not to be considered pure material. I n a few cases, however, the purity is surprisingly high. It is seen that the knock rating is in good agreement with the hydrocarbons known to be present, Without the n-heptane and n-octane the intermediate material is of good antiknock quality. These results, as far as concentrating the good and bad knocking fractions is concerned, are probably reasonable limits beyond which further fractionation is not needed. ADDITIONOF %-HEPTANE AND n-OCTANETO GASOLINE
In order to have a direct comparison with the above data (Figure 4)in which n-heptane and moctane are the bad knocking substances, several blends of pure n-heptane and n-octane were made with two different gasolines. One was a regular B motor gasoline requiring 2.3 @ cc. of tetraethyllead to equal Ethyl Standard; the other, the same Standard reference $3 B fuel B used in making the previous blends, and requir% ing 0.67 cc. of tetraethyllead to equal Ethyl Standard. % The heptane was obtained from the E t h y l G a s o l i n e VOLUHL 7. OrN -rTIN CorPoration, being the same FIGURE 5. EFFECTOF ADDIas is used for making" blends TION OF TI-HEPTANE AND nKNOCK RATINGOF 10 PERCENTBLENDS OF REFRACTIONATED OCTANETO GASOLINE~ REwith isooctane for rating fuels MATERIAL QUIRING 2.3 AND 0.67 CC.9 in terms of octane number; RESPECTIVELY, OF TETRASince the original gasoline was of such wide boiling range it is necessarily of high purity. ETHYLLEAD FOR zERo K~~~~ that separation into good and bad knocking fractions was The n-octane had a refractive RATING most difficult, it is perhaps of more significance to compare the indexof 1.3970 (n2,), a denresults on a refractionation of these first fractions. While a sity of 0.7023 (die), and a freezing point of -56.9' C. These refractionation has not been completed on all the material, properties showed it t,o be very pure. The results of blending are given in Figure 5 . n-Heptane Figure 4 shows the results of refractionation of the material between n-heptane and n-octane. The column 52 feet long blends were used with both fuels, while n-octane was used only and "4 inch in diameter was used with a reflux ratio of 20 :1to with the Standard reference fuel B. At concentrations a t 30:l. which n-heptane and n-octane exist in gasoline-namely, On comparing these data with the original fractionation, it below 5 volume per cent-there is very little difference in their is seen that, whereas on Figure I there is only slight evidence tendency to induce knock. However, since the straight-run of a peak in the refractive-index and gravity curves between Pennsylvania gasoline may easily contain from 10 to 20 per toluene and xylene, it is now very pronounced. This is called cent normal paraffins ranging from heptane to dodecane, it is a naphthene peak, for there are no aromatic hydrocarbons possible for these alone to be responsible for most of the bad present, and the gravity and refractive index are much too knocking characteristics of the gasoline.
2
I
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Comparing these results on the pure hydrocarbons with the two ends of the curve on Figure 4 in which n-heptane and noctane are concentrated, it is seen that the 10 per cent blends of the pure materials check the 10 per cent blends of the bad knocking fractions very \$-ell when using reference fuel B. These data again substantiate the conclusion that the bad knocking fractions, produced from the straight-run gasoline by effective fractionation, are largely normal paraffin hydrocarbons. KSOCK RATIXGO F I I I X T U R E S O F HI-DROCARBONS I n measuring the knock of a gasoline, two ratings are necessary: One is the number of cubic centimeters of tetraethyllead which must be added to the gasoline to equal 74 octane number, or Ethyl Standard; the other, the octane number of the gasoline itself. Though one rating may be known, there is no direct relationship b y which the o t h e r m a y be obtained. However, it has been f o u n d t h a t the octane number and cubic centimeters of tetraethyllead can be correlated fairly well by making a FIGURE6. RELATIONSHIP OF OC- scale such th& a straigrhtTANE N~~~~~ TO A~~~~~ OF !ine relationship results, TETRAETHYLLEAD using a particular gasoline. A s t r a i g h t l i n e also results when the octane number and cubic centimeters of tetraethyllead of several other gasolines are plotted on this same scale. This is shown in Figure 6. This relationship may be useful where other more accurate data are not available. Using this figure, it is possible to obtain with fair accuracy the octane number of a gasoline from the cubic centimeters of tetraethyllead necessary to equal Ethyl Standard. While large additions of tetraethyllead do not define relative knock intensity as accurately as small additions, they are nevertheless very helpful in anticipating what may result when these bad knocking fractions are present in blends. It has also been found that the closer the lead ratings of two gasolines are, the more accurately the knock ratings of blends of these two gasolines can be calculated on a simple additive basis. For example, if the materials in the CSand Cg peaks on Figure 1 with a knock rating above 7 are combined, then calculating from the lead ratings and volumes given in this figure, the rating on an additive basis is 13 cc. of tetraethyllead. As shown on Figure 1 there are fourteen volumes of this material. The blend indicated on Figure 1 and in the section on Fractionation of 510" F. End-Point Gasoline, with a knock rating of 2 cc. of tetraethyllead, was obtained by omitting from the gasoline with a 3.4 lead rating, the material in the CSand Cepeaks with a rating over 7.6 cc. of tetraethyllead (fourteen volumes). As shown in Figure 1, there are fifty-two volumes of this gasoline with a rating of 2 cc. of tetraethyllead. So the addition of these fourteen volumes with a rating of 13, to fiftytwo volumes of gasoline rating 2, should, on an additive basis, produce sixty-six volumes with a lead rating of 4.3. This then, is the blend shown on Figure 1 with a rating of 3.4, and indicates fair agreement. Other similar results indicate that, when more reliable data are lacking, the knock rating of a blend of two gasolines may be considered to be an additive effect of each, particularly so when the two gasolines are not widely different in knock ratings.
IMPROVEJIENTS IN ANTIKNOCK QUALITY While the data above show certain facts regarding the constitution of Pennsylvania straight-run gasoline, they
VoI. 24, No. 5
hardly indicate the results which may be obtained in concentrating the knocking fractions when using more thorough fractionation. I n order to procure this necessary information, the work is being continued on a larger and more efficient scale. These results may then lead to definite conclusions regarding the practicability of effecting the necessary separations in the gasoline. Without intending to be in any way speculative, it is interesting t o note the following points: Since the knock rating of a gasoline may be improved by adding to it a gasoline of higher antiknock rating, or removing from it certain exceptionally bad knocking fractions, a few comparisons of the t M - 0 methods may be noted. From the above data, removing about 20 per cent reduced the knock rating from 3.4 t o 2 cc. of tetraethyllead per gallon. I t would require that at least 30 t o 40 per cent (calculating on the additive basis indicated above) of a gasoline of zero knock rating (74 octane number) be blended with the gasoline of 3.4 cc. rating to produce the same result. Again, referring to the 10 per cent blends of n-octane in Standard reference fuel B (Figure 5 ) , the lead rating was raised from 0.67 t o 1.8 cc. per gallon, or vice versa; eliminating this 10 per cent would have reduced it from 1.8 t o 0.67 cc. of tetraethyllead. I t would have required the presence of 50 to 60 per cent of a zero gasoline in one of 1.8 cc. rating to reduce it to 0.67 cc. of tetraethyllead. In another instance it was necessary t o add 20 per cent benzene t o a good antiknock motor gasoline containing 10 per cent n-octane to bring it back to its original knock rating. While many interpretations such as the above are possible, the primary purpose is to submit these data as essentially fundamental information and as a basis for additional work. The higher-boiling fractions of the gasoline deserve particular study, since they contribute largely to the knock. Through the accumulation and study of such data on chemical composition and knock rating, one a t least of several possibilities may be of practical importance for improving the knock characteristics of straight-run Pennsylvania gasoline. CONCLUSIONS In one fractionation, using the equipment previously described, straight-run Pennsylvania gasoline was separated into fractions of alternate high and low knock rating, or fractions in which straight-chain paraffin, aromatic, and naphthenic hydrocarbons were concentrated. Refractionation enabled some substances to be obtained which closely approximated pure materials both as to physical properties and knock behavior. Any one normal paraffin is present in the Pennsylvania straight-run gasoline to the extent of 2 to 5 per cent. Yet in all probability, they alone, while not totaling over 20 per cent, are largely responsible for the knock. It has been found that the fractionating equipment will effectively concentrate these paraffins to permit their removal from the gasoline. ACKNOWLEDGMENT The assistance of K. A. Varteressian in the fractionations and of W. F. Knop in the knock tests is gratefully acknowledged. LITERATCRE CITED (1) Brown, G. G., and Carr, A. R., IND. ESG.CHEM.,18, 718 (1926). (2) Egloff, G., Nelson, E. F., and Truesdale, P., 011 Gas J., 29, No. 39. f1931\. .., 38 ~. , ---,(3) Fenske, M. R., Quiggle, D., and Tongberg, C. O., IXD. ENG. CHEM.,24, 408 (1932). (4) Geniesse, J. C., and Huff,H. F., I b i d . , 20, 794 (1928). (5) Hill, J. B., Henderson. L. At., and Ferris, S. W., Ibid., 19, 128 (1927). (6) Leslie, R. T., and Schicktanz, S.T., Bur. Standards J . Research, 6, 385 (1931).
(7) Shepherd, A. F., and Henne, A. L., IND.EKG.CHEM.,22, 366 (1930). (8) Shepherd, A. F., Henne, A. L., and Midgley, T., Jr., J . Am. Chem. Soc., 53, 1948 (1931). RECEIVED December 3 , 1931.
