Flow of Gasoline Thickened by Napalm GEORGE A. AGOSTON1, WALTER H. HARTE2, HOYT C. HOTTEL3, WILLIAM A. KLER/13\14, ICAROL J. MYSELS6, HAROLD H. POMEROY, .4ND JOHN M. THOMPSON7 Massachusetts Znstitute of Technology, Cambridge, Mass., and Stanford Unieersity , Stanford, Calif.
G
ASOLINE thickened with Tapalm was the main fuel used by
the United States for flame throwers and, in the last stages of World War 11,fire bombs. I n the course of work on the design and testing of flame throwers, it became possible and useful to investigate the flow of this thickened gasoline through pipes. Because of wartime conditions, the experiments were all rather hurried and can lay no claim to high precision, but it is believed that t.he main results obtained are significant'. They cover an essentially unexplored range of flow rates for this type of material and bring out a new type of flow anomaly which becomes apparent a t very high rates of flow: the apparent, reduct'ion of viscosit'y by t.he addition of a thickening agent. Napalm is a granular solid which readily disperses in gasoline at room temperature and gives rapidly a transparent, homogeneous, stringy jelly ( 3 ) . Chemically, Ic'apalm is primarily an aluminum disoap corresponding to the formula AlOHRz derived from a mixture of commercial coconut, oleic, and naphthenic acids. It cont,ains also some uncombined acid, water, and inorganic impurities (4). The consistency of Napalm jellies is variable, depending on many factors, but generally 2 to 4% of Napalm gave a definitely stringy jelly and 10 to 12% gave a very elastic, ahnost solid, one. It was generally measured quantitatively by the weight required to push a flat plunger at a specified rate through t.he jelly in a standardized Gardner Mobilometer and was expressed in grams Gardner. EXPERIMENTAL
The equipment used in preparing and handling the jellies comprised 700-gallon tanks mounted on wheels, trucks to move these tanks, a truck-mounted 300-gallon mixer, and a 2000-pound-persquare-inch air-compressor. The jellies were stored and aged in the TOO-gallon tanks a t least overnight before use. They were then propelled from one tank to another through a pipe and a positive displacement meter (Niagara Specialty oil meter No. 2 GV). The pressure drop along the pipe was measured along the length of the pipe a t several points on Bourdon gages, held by short s/s-inch nipples which did not penetrate into the inside of the pipe. The jellies could be returned t o the storage tank through the pipe and a bypass around the meter. The pipes were standard black pipes l/2, 1, and 2 inches in diameter and 21 t o 36 feet in length. Seven calibrated gages were attached t o each pipe, the first two close to the entrance and the others a t 3- t o 5- foot intervals. The jellies had nominal consistencies of 110, 400, and 850 grams Gardner, with small variations for which correction could easily be made. Compressed air from cylinders, with proper reduction gages. was used to supply pressures up to 130 pounds per square inch to drive the jellies through the pipe and meter. This gave pressure
1 Present address, J e t Propulsion Laboratories, California Institute of Technology, Pasadena, Calif. 2 Present address, McGraw-Hill Publishing Co.. New York, S . Y. s Present address, Massachusetts Institute of Technology, Cambridge. Mass. 1 Present address, Kaiser Aluminum and Chemical Co., Permsnente. Calif. 5 Present address, Cniversity of Southern California, Lo6 Angeles 7, Calif. 6 Present address, Mereo Centrifugals, San Francisco, Calif. 7 Present address, Minnesota Mining and Manufacturing Co., St. Paul, Minn.
drops from 0.1 pound per square inch per foot, which was about the accuracy of measurements, to 3.4 pounds per square inch per foot, and flow rates up to 80 U. S. gallons per minute. RESULTS
The pressure drop per unit, length, dP/dL, was subst,antially constant throughout. the pipe except for entrance effects in about the first 50 pipe diameters, for any rate of flotv and any one jelly. Its value increased rapidly wit,h the consistency of the jelly and slowly Tith the rate of flow. The presentation of the raw values is omitted, a@t,heir absolute value seems to be of little importance and they may be readily reconstructed from Figure 1, which gives the simplest correlation to which the authors arrived. For streamlined flow at a rate Q (gallons per minute) in a pipe of diameter D (inches) under a pressure gkadient dP/dL (pounds per square inch per foot) for a Newtonian liquid there is a direct proportionality between Q/D3(which is proportional to the average ratte of shear) and D dP/dL (which is proportional to the average shear stress). For the highly non-Newtonian jelly a logarithmic plot of t,hese two quantities was the best way of bringing all points for a given jelly close to a smooth line, but instead of a straight 45' line, the shape shown in Figure 1 was obtained. The lines for each jelly xere parallel to each other 40, where G is thr and by dividing the D dP/dL value by G Gardner consistency, all the points were brought close t,o a single smooth line as shown in Figure 1. The deviation of any point from this line is less than about 50%, which is probably no more than the reproducibility of the data, although the line correlates data covering the whole broad range of consistencies, pipe diameters, and flow rate studied. Values obtained completely independently by a group working a t the Eastman Kodak Co. ( 2 ) on similar jellies but using a gear pump instead of air pressure for driving the jelly agreed within the same limit with the aut'hors' data, suggesting that pumping does not affect greatly the flow characteristics of these jellies. On the other hand, values obtained with gasoline thickened with purposely or accidentally peptized fuels seemed always to give much higher pressure drops for the same Gardner consist,ency. This lack of agreement is not surprising if one remembers that the flow in the Gardner Mobilometer consists entirely of ent'rance and exit effects. The authors did not observe any of the surface effects noted by Wood, Nissan, and Garner (6) on peptized aluminum stearate jellies, but they were working with diameters ( '/z inch and above) where Wood et al. found such effect's to be negligible. The two extremes of the correlating curve of Figure 1 are of some interest. Even a t the lowest rates of flow observed, there is no tendencjtoward Newtonian flow, and the pressure drop seems to tend t,o a constant value for each pipe diameter and each consistency. Yet these jellies do not have a true yield value, for aft,er a sufficient time all acquire a flat surface under t4heinfluence of gravitational and surface forces. What happened a t extremely low rates of flow may be inferred from the fact that when the flow in the pipes was stopped by closing a valve, the pressure drop did not become zero immediately, but. decreased rapidly a t first and then slowly. The data col-
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Figure 1. Relation of Consistencj , Pipe Diameter, and Flow Rate t o Pressure DPOQ
The flow under these conditions ie infinitesimal by ordinary standards, and while the jelly has no true yield value, it does haye a practical one at which the elastic structure breaks. This pracrical yield value for the jellies used in this investigation seems to be about 0.001 Q dP/dL (G 40) gallon pounds per square inch/ foot gram. The upper extreme of the correlation curve becomes of interest, as shown in Figure 2, when compared v i t h the calculated behavior of pure unthickened gasoline. At Ion. rates of flow the pressure drop (plotted as D dP/dL on the ordinate) for the gasoline is, ae R ould be expected, dwarfed by that of the jelly, the ratio being about 10,000 for the least viscous mixture. At higher rates of flow, however, the pressure drop of the pure gasoline increaee? veiy rapidly while that of the thickened gasol~heincreases very s l o ~ ~ l pThe . two curves seem t o intersect just a t the point where the data obtained in the above experiments ended. But uncertainties as to the assumptions on which the calculations are bawd cast eorne doubt upon the reality of this phenomenon. A new series of experiments was, therefore, conducted in which ihe pressure drop at the same rates of flov, in the same pipe,
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lected on this point are meager and relatively inaccurate because of the unsteady state of the system, but qualitatively the effect wa8 always unmistakably present. Thus, for example, the pressure drop of an 850-gram Gardner jelly in a '/a-inch pipe decreased from 0.175 to 0.158 pound per square inch per foot between 0.5 and 5 minutes after flow stopped; in a 2-inch pipe, it decreased from 0.34 to 0.23 pound per square inch per foot b e h e e n 0.5 and 2 minutes and was negligible after 8 minutes. This suggests that once a strain is set up in the jelly, it takes a relatively long time to relax, even in the absence of any measurable flow. This is in agreement with Carver and Van Wazer's &dings (1) of a definitely elastic slowly reforming structure in Kapalm jellies. It seem8, therefore, that small stresses set up elastic strains in these systems and flow occurs only by the relaxation of these strains.
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Pressure Drop of Pure Gasoline and Dilute Jelly
May 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
using the same gages, was compared for pure gasoline and for a very dilute jelly prepared from the same gasoline. The rate of flow was measured by weighing the discharge over a timed interval in order to avoid any uncertainty inherent in volumetric measurements. The gages were attached to sleeves silver-soldered over a 1/16-inch clean hole drilled in the pipe wall, thus avoiding any inch, and the disturbance of the flow. The pipe diameter was consistency of the jelly was estimated a t 20 grams Gardner. The results obtained are shown in Figure 3, along with the calculated line according t o Fanning's correlation. The pressure drop for gasoline was found to be more than that calculated, but both the experimental and the calculated values for pure gasoline are definitely higher than those for the jelly a t flow rates above 2 gallons per minute. The difference between the calculated and experimental values for pure gasoline is probably due to uncertainties introduced by pipe irregularities and roughness. The difference between the experimental curves for the gasoline and the jelly involves no calculations or assumptions. On a purely experimental basis this is the rather paradoxical case of a thickened, jellified fluid offering less resistance to flow than the unthickened liquid from which it was prepared (5). The viscosity of jellies is known always to decrease a t high rates of shear, presumably because of the breaking of bonds between colloidal particles a t a faster rate than they can reform. The
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limit of this process, however, cannot be expected to give a viscosity lower than that of the pure liquid. The explanation must, therefore, lie in a different mode of flow of the jelly and of the gasoline. The flow of gasoline ia turbulent, but no information is available about the flow of the jelly. A less turbulent, more streamlined flow of the jelly could reduce the pressure drop even while the viscosity remains much higher. Whether this is indeed the case, and whether the same paradoxical behavior is shown by other jellies, remains t o be investigated fully. LITERATURE CITED
(1) Carver, E. K., and Van Wazer, J. R., J . Phys. & Colloid Chem., 51, 751 (1947). (2) Eastman Kodak Co., Monthly Progress Report, November 1944. (3) Fieser, L. F., Harris, G. C., Hershberg, E. B., Morgans, M., Novello, F. C., and Putman, S. T., IND. ENG.CHEM.,38, 768
(1946). (4) Mysels, K. J., Ibid., 41, 1436 (1949). ( 5 ) Mysels, K. J., U. S. Patent 2,492.173 (1949). (6) Wood, G. F., Kissan, H. H., and Garner, F. H., J . Inst. Petroleum, 33, 73 (1947). RECEIVED for review August 11, 1953. ACCEPTED January 7, 1954. Work was conducted in 1945 a t Edgewood Arsenal incidental t o a joint Chemical Warfare Service and National Defense Research Committee program of evaluating flame throwers. Reported in part in the B.S. thesis of Walter Harte and John Thompson.
Sodium-Promoted Condensation of Organic Halides and Carbonyl Compounds CHARLES E. FRANK' AND WALTER E. FOSTER2 Applied Science Research Laboratory, University of Cincinnati, Cincinnati 21, Ohio
T"
1 sodium-promoted condensation of organic halides and carbonyl compounds has received relatively little attention, largely because of the great convenience and versatility of the analogous Grignard reaction. hiorton and Stevens (f1) demonstrated this reaction in 1931, obtaining better than 90% yields of triphenylmethanol (triphenylcarbinol) from the condensation of chlorobenzene and ethyl benzoate with sodium. Other reactions of this type in which sodium was found effective have included the synthesis of highly branched alcohols unobtainable by the Grignard condensation-for example, Bartlett and Schneider ( d ) obtained 3-fert-butyl-2,2,4,4-tetramethyl-3-pentanol(tritert-butylcarbinol) by the reaction of tert-butyl chloride, methyl pivalate, and sodium sand. Cadwallader, Fookson, Mears, and Howard ( 3 ) extended this condensation t o include additional examples of branched halides, esters, and ketones.
PROCEDURE
The ease of handling and high reactivity of the finely divided sodium dispersions recently described ( 5 , 6 ) prompted the present investigation of the usefulness and limitations of sodium in the halide-carbonyl condensation. In most of this work, as in that of Cadwallader et al., the halide and carbonyl compound were added concurrently to the solvent-sodium mixture. B y this procedure, 1 Present address, Research Division, Sational Distillers Products Corp., Cincinnati, Ohio. * Present address, Ethyl Corp., Baton Rouge 1, La.
illustrated below, neither the organosodium intermediate nor the carbonyl compound is present in any substantial concentration, and side reactions are reduced to a minimum. A 1-liter round-bottomed flask was fitted with a mercurysealed stirrer, a dropping funnel, a thermometer extending into the reaction mixture, a nitrogen inlet tube, and a reflux condenser vented through a cold trap and oil bubbler. After purging with nitrogen, 200 ml. of dry iso-octane (2,2,4-trimethyl pentane), 25.4 grams of a 50% dispersion of sodium in dibutyl ether (0.55 gram atom of sodium), and a few crystals of benzophenone (to activate the sodium) were added. Benzyl chloride (3.2 grams) in 30 ml. of iso-octane then was added at 25' to 30" C. over a 20minute period; there was no evidence of reaction a t this point. A solution of 28.5 grams of benzyl chloride (0.25 gram-mole total) and 14.5 grams of acetone (0.25 ram-mole) in 240 ml. of iso-octane was added dropwise over a 3-tour period. At the beginning of this addition, the mixture began darkening and heat was evolved. The flask then was cooled to about '5 and the reaction was completed a t this temperature. The mixture was quenched under a nitrogen atmosphere by the dropwise addition of 100 ml. of water while the temperature was held a t 10" to 20" C. Chloride titration of the aqueous layer showed that 98% of the benzyl chloride had reacted. The oil layer was washed, dried, and fractionated to obtain 12.4 grams of toluene (27%) and 31.8 rams of 2-benzyl-2-propanol (42.5%). The higher boiling resifue (20%) comprised acetone self-condensation products and a small amount of dibenzyl. The reaction of benzyl chloride and acetone was studied in some detail to observe the effects of temperature, solvent, and other reaction variables. Increase in the reaction temperature
