Flztrnmability of Carbon Disulfide in Mixtures of Air and Water Vapor M. G. ZABETABIS AND G. W. JONES Gaseous Explosions Branch, Explosives a n d Physical Sciences Division, B u r e a u of M i n e s , P i t t s b u r g h , P a .
L
I M I T S of flammability of carbon disulfide in air and other atmospheres as determined by various workers have been summarized ( 1 ). The present investigation was conducted t o determine the minimum oxygen required for flame propagation through carbon disulfide-air-water vapor mixtures at 100 C. and 1-atmosphere pressure. The use of water vapor as a flame-quenching agent is old. It has been used effectively as an inert agent in many processes a t elevated temperature, but few laboratory tests have been conducted t o date u-ith combustible vapor-air-water vapor mixtures. O
r(
HzOVAPOR IN MIXTURE, PERCENT BY VOLUME
Figure 2. Limits of Flammability for Carbon Disulfide Vapor-Air-Water Vapor Mixtures at Atmospheric Pressure and 100" C.
sure are given in Table I, listed in the order of increasing carbon disulfide and/or water vapor content. As the minimum oxygen content required for flame propagation was the principal objective, the upper limit data were not obtained. The upper limit of
TABLEI. LIMIT-OF-FLAMMABILITY TEST DATA ON CARBOX DISULFIDEVAPOR-AIR-WATERVAPORMIXTURESAT 100' C. AND ATMOSPHERE PRESSURE Composition of Mixture, % oxygenContent by Volume of iMixture, Propagated CS1 Hr0 Aira % b y Volume Flame? NO. 1.19 0 98. 81 20.7 No 7 1.21 0 98.79 Ye5 6 20.7 1.25 5.80 92.95 Ye5 19.5 8 NO 19.2 1.19 7.27 91.54 9 No 10 1.27 18.7 9.16 89.57 10.1 No 11 1.30 18.5 88.60 11.0 87.55 Yea 12 1.45 18.3 1.75 17.3 82.46 15.8 Yes 13 24.8 15.4 S O 1.57 73.63 15 15.3 No 25.6 14 1.53 72,87 14.7 27.7 1.95 70.35 Yea 16 13.7 Yea 32.0 17 2.47 65.53 61.11 No 12.8 36.6 2.29 18 41.1' 2,5., 19 11.8 56.37 Yea 11.6 No 42.3 55.21 20 2.49 10.8 21 45.6 2.66 51.74 Yea 9.71 22 50.7 2.89 46.41 Yes 8.77 46 54.8 3.30 41.90 Yes 3.33 41.77 No 8.74 47 54.9 8.75 54.7 3.50 41.80 Yea 44 54.5 8.78 45 3.54 41,96 Yes No 7.93 42 57.8 4.30 37.90 Y e5 7.87 41 57.8 4.60 37.60 No 7.62 36.41 40 58.8 4.79 Yes 8.20 55.3 5.52 39.18 26 7.76 57.6 Yes 27 5.32 37. OS 7.73 57.3 5.75 36.95 28 No N O 7.40 36 58.6 6.04 35.36 12.1 46.6 8 64 Yes 49 41.30 13.0 46.4 40.60 No 8.50 59 a Percentage of air obtained as difference between 100% and percentages of CS2 and HzO. Figures carried in this column are used only t o obtain oxygen content of mixture; they are not t o imply experimental accuracy sufficient to warrant four significant figures.
Test
Figure 1. Liquid Feed Device with Continuously Variable Speed Driving Disk
The following materials were used for the present investigation: Carbon disulfide, J. T. Baker Chemical Go., Lot 92250. Water, distilled. Air, dried and filtered. LIMITS O F FLAMMABILITY
T h e U. S. Bureau of Mines elevated-temperature apparatus
( 4 ) was modified by the addition of a second liquid-feed device whose feed rate could be varied continuously. It differs mainly in the addition of a variable-speed driving head (Figure 1; compare with Figure 5, 4). The limit-of-flammability data obtained for the system carbon disulfide-air-water vapor a t 100 C. and 1-atmosphere presO
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Vol. 45, No. 9
INDUSTRIAL AND ENGINEERING CHEMISTRY
flammability a t 60°C. (2) was used t o comp1t:te the limit-of-flammability curve given in Figure 2, although it is probably a little low, as the current investigation gives values at 100 ' C. Using Figure 2 and a procedure described elsewhere ( S ) , the minimum oxygen required for flame propagation in a carbon disulfide vapor-air-water vapor mixture at 100" C. and l-atmosphere pressure is found to be 7.6%. On a weight basis, with all constituents initially at 100" C. and 1-atmosphere pressure 4.3 pounds of water are required per pound of carbon disulfide t o extinguish a carbon disulfide vapor-air fire; this corresponds t o 3.4 gallons of water per gallon of carbon disulfide, on a volume basis. CONCLUSIONS
The lower concentration limit of flammability of carbon disulfide in air a t 100" C. and 1-atmosphere pressure is 1.20% carbon disulfide by volume in the vapor-air mixture. This is equivalent to a concentration of 41.2 mg. of carbon disulfide per liter of air at
normal temperature and pressure and to a fraction of stoichiometric of 0.184. T h e minimum amount of oxygen required for flame propagation through a mixture of carbon disulfide, air, and Yater vapor a t 100" C. and 1-atmosphere pressure is 7.6% by volume. T o extinguish a carbon disulfide vapor-air flame under all conditions (with the carbon disulfide initially at atmospheric pressure and 100" C.) requires 4.3 pounds of water vapor per pound of carbon disulfide vapor, or 3.4 gallons of water per gallon of carbon disulfide on a volume basis. LITERATURE CITED
(1) Coward, H. F., and Jones, 0 . W., U.S . Bur. M i n e s , Bull. 503 (revision of BUZZ.279), 29-30 (1952). (2) W h i t e , A. G., J . Chem. Soc., 121, 1244-70 (1922). (3) Zabetakis, hl. G., a n d Richmond, J. IC, "Limits of Flammability of Complex Hydrocarbon Fuels at Low Pressures and Temperatures," Baltimore, Williams and Wilkins Co., August 1953 (4) Zabetakis, &I. G., Scott, G. S., a n d Jones, G. W., IND.ENG. CHEM.,43,2120-4 (1951). for review Febiuary 5,1953. RECEIVED
ACCEPTED hIay 23, 1953.
Effect of Temperature upon Rate of Oxidation of Rub NATURE OF RESULTANT DETERIORATION J. REID SHELTON, FRED J. WHERLEYl, AND WILLIAM L. COX Case Institute of Technology, Cleveland 6, Ohio
A
CCELERATED tests are widely used t o compare the rela-
tive resistance of rubber stocks to aging. These tests usually involve elevated temperature in the presence of air or oxygen, and may also involve increased pressure. It is frequently desired t o translate the results of such short-term tests into predictions of probable aging behavior during storage or in service. Many observers have indicated, hoviever, that a change in the temperature frequently brings about a change in the nature of the aging ( 3 ,6, 7-9, I S , 15, 1 7 ) . For example, in the case of natural rubber, a change in the nature of the oxidation was suggested in the vicinity of 70" t o 80" C. ( 3 ,8, 1 5 , 1 7 ) . Kemp and corn-orkers (4,5 ) have demonstrated that, in the case of an uninhibited natural rubber gum stock, the deterioration of tensile strength was a linear function of the amount of oxygen absorbed, as measured by the gain-in-weight method. The amount of oxygen required to produce a given deterioration varied linearly with the temperature, indicating a continuing change in the nature of the aging, rather than an abrupt change in the oxidation mechanism. The quantjty of oyygen required t o produce a given change in tensile decreased as tliii temperature of oxidation increased. A direct relationship has also been observed in thia laboratory (10,12, 16) between the volume of oxj Ten absorbed, a t constant temperature and pressure, and the changes in physical properties. A study of the effect of changes in temperature and in oxygen concentration, upon the rate of oxidation and the nature of the accompanying degradation, was undertaken to see if the variations that result could be correlated in a regular fashion. If so, i t should be possible t o extrapolate the results obtained at higher temperatures in oxygen, so as to predict approximately the aging behavior in air at room temperature. The trends observed a t different partial pressures of oxygen have been reported elsePresent address, B. F. Goodrich Research Center, BreoksviUe, Ohio.
where (II), and this paper describes the effect of temperature variations with gum and black stocks of both natural rubber and GR-S. EXPERIMENTAL PROCEDURE
The volumetric method of oxygen absorption was used. The equipment and procedure have been described in other papers from this laboratory (1,12, 16). Five stocks were studied-GR-S and Hevea, gum and black vulcanizates-as shown in Table I, including both inhibited and uninhibited stocks of the Hevea black. Samples were aged a t four temperatures-50°, 70°, go", and 110" C.-in oxygen a t 1 atmosphere pressure. Dumbbell tensile specimens, 4.5 inches long, were cut from sheets approximately 0.040 inch thick. Prior work ( I ) has shown t h a t this thickness is satisfactory to
TABLE I. COMPOSITION O F STOCKS Smoked eheet
GR-S A? b Paraflux Bardold
Gum
...
... ...
. I .
...
... ...
...
50
...
.2. .
~ @ ~ , ~ $ d Zinc oxide Sulfur Santocure e Thiotaxe Bantoflex Cure time a t 280' F., min.
;lC.i P.~ ~Hall~ Co: ~ n " 4~ , ~
GR-S Stocks
Hevea Stocks Gum Blackn 100 100
3
5 3
...
0.75 1.5 40
100
4
1
3 3 1
Black
...
100 4 4
2.4 45 2.4 2 1.2
5
2 1.2
...
...
. ..
...
1.5 40
...
60
60
f ~ d 2 , ~ ~ ~ ~ - ~ - ~ ~ ~ ~ t ~ ~ ~ ~ ~ ~ ~ d e d .
C
~
~
and Dye
~
~
cO.
~
?
$
~
;
~
