Form of a Pressu WORDEN WARING' Shell Development Co., Emeryville, Calif,
Experimental
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(1) (2)
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6
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(7) Negative a t T less than D/4E.
+
+
0
+
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+
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+ o
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At temperatures above Z)nain., the first and second derivatives must both be positive and the third seems also to be positive, at least up to very near the critical temperature. A t the critical point A H / A Z remains finite although AH and AZ separately go to
April 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
Finally, the function used here, A H / A Z against T , is fairly sensitive and it is recommended for testing the consistency and smoothness of values tabulated for saturation properties of pure substances. LITERATURE CITED
(1) Albright, L. F., and Martin, J. J., IND.ENO.CHEW,44, 188 (1952). (2) Am. SOC.Refrig. Engrs., New York, N. Y., "Refrigerating Data Book," pp. 78-9, 1943. (3) Barkelew, C. H., Valentinc, J. L., and Hurd, C. O., Chem. Eng. Progr., 1, No. 1; Trans. Am. Inst. Chem. Engrs., 43, 25 (1947). (4) Canjar,'L. N,, Goldman, M., and Marchman, H., IND. ENG. C H E M . , 1186 ~ ~ , (1951). (5) Joffe, J., J . Am. Chem.SOC., 69,1216 (1947).
(6) Matthem, C. S., and Hurd, C. O., Trans. Am. Inst. Chem. Engrs., 42,55 (1946). (7) Meyers, C. H., Cragoe, C. S.,and Mueller, E. F., J . Research Natl. Bur. Standards, 39,507 (1947). (8) O'Brien, L. J., and Alford, W.'J., IND.ENG.CHEM.,43, 506 (1951).
763
(9) Organick, E. I., and Studhalter. W.R.. Chem. E ~ QProgr., . 44, 847 (1948). (10) Osborne, N. S., Stimson, H. F., and Ginnings, D. C., J . Research Natl. Bur. Standards, 23, 261 (1939). (11) Plank, R., and Riedel, L., Texas J . Sci., 1, 86 (1949). (12) Prengle, H. W., Jr., Greenhaus, L. R., and York. R., Jr., Chem. Eng. Progr., 44, 863 (1948). (13) Rynning, D. F., and Hurd, C. O., Trans. Am. Inst. Chem. Engrs., 41,265 (1945).
(14) Sage, B. H., and Lacey, W. N., "Thermodynamic Properties of the Lighter Paraffin Hydrocarbons and Nitrogen," pp. 716, New York, American Petroleum Institute, 1950. (15) Smith, J. M., Chem. Eng. Proor., 44, 521 (1948). (16) Stearns, W. V., and George, E. J., IND.ENG. CHEY.,35, 602 (1943). (17) Stuart, E. B., Yu, K. T., and Coull, J., Am. Doc. Inst., Document 2753; supplement to Chem. Eng. Progr., 46, 311 (1950). Ex'G.CHEM.,42,1514 (1950). (18) Thodos, G , IND. (19) Walters, C. J., and Smith, J. -M., Chem. Eng. Progr., 48, 337 (1952). (20)
York, R., Jr., and White, E. F., Jr., Trans. Am. Inst. Chem. Engrs., 40,227 (1944).
RECEIVED for review April 13, 1953.
ACCEPTEDDecember 12, 1953.
Explosive Properties of Sugar Dusts R. L. MEEKIAND J. M. DALLAVALLE Georgia Institute of Technology, Atlanta, Ga.
M "
to a standard source of ignition (3, 7, 8); the ignition temperaTRES of flammable gases and air will produce an tures of dust clouds (1, 2, IO); and maximum pressures and explosion if two basic conditions &resatisfied-a suitable rates of pressure rise from explosions of dust cloud8 of various mixture of the gases and an ignition source, electrical or thermal, concentrations. There have also been several studies on the sufficiently intense to ignite the mixture. The gas molecules in prevention and venting of various kinds of dust explosions ( 9 , l J ) . contact with the heat source ignite, and they in turn ignite the gas Geck ( 4 )has recently reviewed the history of sugar dust explosions surrounding them. This process continues and a flame propagain German sugar factories, but has given few details regarding tion results which, under proper conditions, leads to a rapid inthe conditions under which the explosions took place. crease of pressure in the form of an explosion. As the proportion The present work constitutes an attempt t o obtain a better of the flammable gas to the supporting gas (usually air or oxygen) understanding of the fundamental nature of dust explosions. It is decreased, a lower limit of explosiveness is reached a t which concerns a study of the explosibility of three different sugarspoint it can be imagined that the combustible gas molecules are dextrose (CeHlzOe), sucrose (C12H22011), and raffinose ( C18H3201e). too widely separated to support the rapid flame propagation Sugars were selected rather than other materials because they needed for an explosion. could be obtained with a high degree of purity, and because they I n the case of a dust explosion, every condition necessary for a gaseous explosion must be satisfied. The dust concentration represented a series of chemically related substances. Thus, for example, the effect of the number of carbon atoms in three sugars must exceed a minimum explosive limit, and there must be a suitable ignition source to initiate flame propagation and cause st8 related to maximum explosion pressure could he studied. The the explosion. Particle size or surface must also be considered. properties of the sugars investigated are shown in Table I. In addition to the three basic factors affecting dust explosions, numerous others affect the ease of ignition of the dust as well as the speed and TABLE I. EXPLOSIVE PROPERTIES OF SUGARS INVESTIGATED effectiveness of the flame propagation through Max. Max. R a t e Min. Explos. Opt. Press. the dust cloud. Among these are various chemSpecific Explos. Press., Explos. Increase ical and physical factors such as atmospheric Surface Conon. Lb./Sq. Inch Conon Lb./Sq. Inbh/ humiditv, moisture of the dust, dust and gas Sugar Sq. Cm./'c. G./Cu. Mkter Gage G./Cu. M h e r Sea. " , composition, and heat of combustion of the dust. Hartmann (6) and his coworkers have presented a comprehensive study of the effects of these "secondary" factors. Most of the previous work done on dust explosiveness has been primarily concerned with studies of the relative flammability of dusts-i.e., the percentage by weight of inert dust, usually calcined fuller's earth, required in a mixture of flammable dust t o prevent ignition and flame propagation when a dust cloud of the mixture is exposed Present address, Research Division, Lion Oil Co., E l Dorado, Ark. 1
Dextrose
Sucrose
4500 2930 2350 1480 1330 3830 2950 2350 1800
1320 3700 2980 2270 1980 Dextrose Sucrose ~afinose
...
... ...
20 110 220 300
...
40 120 180 320
...
150 330 500
...
72 68 65
57
0 60 56 52 42 0 41 37 33 0
Extrapolated Optima 87 70
... ... ...
50
310 360 400 440
245 220 200 160
240 280 320 450
155 160 125
...
...
350 470 550
90 70
...
... 55
...
60 ...
180 150 100
300 240 120
