September, 1930 (26) (27) (28) (29) (30) (31) (32) (33) 434)
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
hlixter, Am. J . Sci , 40, 23 (1916). Peters, Eng. Mzn. J., 77, 881 (1904). Peters, “Principles of Copper Smelting,” McGraw-Hill, 1907. Peters, “Practice of Copper Smelting,” McGraw-Hill, 1907. Potts, Inst. Mining Met., Bull. 299 (August 15, 1929). Ralston, Bur. Mines, Bull. 298 (1929). Roth, Z . angew. Chem., 42, 981 (1929). Roth and Bertram, Z Elektrochem., 36, 297 (1929). Schenk, Slahl Ezsen, 46, 655 (1926).
963
Sosman and Hostetter, J. Am. Chem. SOL.,38, 807 (1916). Tammann and Batz, Z. anorg. allgem. Chem., 161, 136 (1926). Tigerschiold, Jernkontorets Ann., 107, 67 (1923). Veil, Compt. rend., 188, 330 (1929). Walden, J. Am. Chem. SOL.,30, 1360 (1908). Wartman and Oldright, Bur. Mines, Repfs. Investigations 2901 (1928). (41) Wohler, Martin, and Schmidt, Z . anorg. allgem. Chem., 127, 273 (1923).
(35) (36) (37) (38) (39) (40)
Extinction of Ethylene Dichloride Flames with Carbon Dioxide’ G. W. Jones and R. E. Kennedy PITTSBURGH EXPERIMENT STATION, u. s. BUREAUO F MINES, PITTSBURGH, PA.
T
HE production of ethylene dichloride has greatly increased during the past few years, owing largely to its increased use as a solvent for oils, fats, and waxes, and as a fumigant and insecticide. For the latter uses the ethylene dichloride, which is a liquid with boiling point 83.5 O C., is vaporized into closed spaces in the proper conccntrations t o kill the vermin. Ethylene dichloride vapor is combustible and its extensive use as a fumigant arid insecticide introduces haAards due to possibility of explosions, especially when used in large enclosed spaces. Considerable damage might result should an explosion take place during fumigation. At the request of the Carbide and Carbon Chemicals Corporation, an investigation was made by the United States Bureau of Mines to determine the limits of inflammability of this vapor when mixed with air and the amounts of carbon dioxide whicbh must be added to the ethylene dichloride vapor to render it non-inflammable in all proportions when mixed with air.
it is desired to destroy-that is, they absorb the ethylene dichloride a t a faster rate and are more quickly killed. Results
The areas of inflammability of ethylene dichloride, carbon dioxide, and air mixtures are shown graphically in Figure 1. It also shows how the limits of inflammability of ethylene dichloride are narrowed by the addition of carbon dioxide. I n this curve the values for “Carbon Dioxide in Atmosphere” refer t o the percentage of carbon dioxide in the atmosphere before the addition of the ethylene dichloride. For example, if carbon dioxide is added t o a closed space containing air until the “atmosphere” contains 21 per cent carbon dioxide, then
Procedure Samples of ethylene dichloride were submitted to the bureau by the firm mentioned and tests made in the inflammability apparatus described in a previous publication (2’). Previous tests have shown that results obtained in this apparatus are very close to those obtained in large volumes and are practically comparable as to conditions with those in which ethylene dichloride 1s used in practice. The explosion tube, mounted vertically, was 4 feet long and 2 inches in diameter. Flames were propagated from the bottom to the top. As ethylene dichloride does not have sufficient vapor pressure a t ordinary laboratory temperatures to give higher limit mixtures (air saturated with ethylene dichloride at laboratory temperatures is explosive), it was necessary to conduct the tests a t elevated temperatures. A temperature of 100” C. was chosen to insure complete vaporization of the ethylene dichloride a t the upper-limit mixtures. The determined limits of inflammability of ethylene dichloride in air (dried with CaC12) r e r e 5.8 per cent lower and 15.9 per cent higher by volume a t 100’ C. The lower limit a t 22’ C. (laboratory temperature) was 6.2 per cent by volume. Tests were made to determine the amounts of carbon dioxide which must be added to ethylene dichloride mixtures to render them non-inflammable. Carbon dioxide has a twofold value: It reduces the explosibility of ethylene dichloride mixtures; and it has been shown by Cotton and Young (1) that it stimulates the respiratory processes of the vermin which 1 Received May 13, 1930. Published by permission of the Director, U. S Bureau of Mines (Not subject to copyright.)
I
! I
I
l
~
l
I
i
1
I
I
~ ‘ I i i i L I
1
Figure 1-Limits of Inflammability of Ethylene Dichloride i n Mixtures of Air a n d Carbon Dioxide
ethylene dichloride can be added in any proportions without danger of explosion. The dotted line in Figure 1 indicates the mixtures containing oxygen and ethylene dichloride in the proportions to give complete combustion. As the preferred practice is to mix the carbon dioxide with the ethylene dichloride before introduction into a closed space, the amounts of carbon dioxide which must be added are better shown in Figure 2, which gives the volumes of carbon
INDUSTRIAL AND ENGINEERING CHEMISTRY
964
dioxide per volume of ethylene dichloride that must be added to render the mixtures non-inflammable. It is seen that to render ethylene dichloride non-inflammable in all proportions when mixed with air it is necessary that 2.3 volumes or more of carbon dioxide be mixed with 1 volume of ethylene dichloride. These results show that 25
26
15 5
24 16 0
22
16 5
i
I20
Vol. 22, No. 9
Likewise, the volumes of nitrogen required to extinguish the different flames for which values have not been determined may be roughly estimated in a similar manner. The combustible gases in which the extinctive effect of both nitrogen and carbon dioxide have been determined show that it requires 1.57 to 1.87 more volumes of nitrogen than carbon dioxide to extinguish the different flames, the ratio varying with the different combustibles. On this basis, then, it should require 2.3 X 1.87 = 4.3 volumes of nitrogen per volume of ethylene dichloride to render such mixtures non-inflammable. All the foregoing values are given on a volumetric basis. On a weight basis, as the density of carbon dioxide is 44.5 per cent that of ethylene dichloride, if the two are mixed in the proportions of 1.02 pounds of carbon dioxide to 1 pound of ethylene dichloride, the resultant mixtures should be noninflammable when mixed with air a t 100" C. and atmospheric pressure. Table I-Extinction of F l a m e s b y Addition of Nitrogen, Carbon Dioxide, or Carbon Tetrachloride
I COMBUSTIBLS GASOR
VAPOR
I INERTS NECESSARY TO RENDER 1 VOLUME COMBUSTIBLB LrMITs OF UNDER INFLAMMABILITYNON-INFLAMMABLE CoNDITIoNs OF WITH AIR AT L. T.P. Lower
Hydrogen Ethylene Ethane Ethylene oxide Methane Ethylene dichloride Carbon monoxide a
VOLUMES OF CARBON ViOXlDE PER VOLUME ETHYLENE DICHMRIDE
Figure 2-Limits of Inflammability of Ethylene Dichloride and Air When Mixed w i t h Various Proportions of Carbon Dioxide
ethylene dichloride is much more easily extinguished by carbon dioxide than other typical combustible gases, as shown by Table I. For example, hydrogen requires 10.2 volumes of carbon dioxide, ethylene, 9.0, and ethylene oxide, 7.3, whereas ethylene dichloride requires only 2.3 volumes. The table also gives the volumes of nitrogen that must be added to several combustible gases to render them non-inflammable when mixed with air. These values are given for comparison with the amounts of carbon dioxide that must be added. For methane the volumes of carbon tetrachloride are also included. The extinctive effectof carbon dioxide, itrogen, and carbon tetrachloride appears to be due largely to the heat capacities of the added inert gas or vapor. Although the extinctive effect of carbon tetrachloride has been determined for methane flames only, the approximate amounts of carbon tetrachloride required for the extinction of the other combustibles given in the table may be estimated from the amounts of carbon tetrachloride and carbon dioxide required in the case of methane flames. For example, it requires slightly less than one-half (44per cent) the number of volumes of carbon tetrachloride as of carbon dioxide to extinguish methane flames. On this basis the amountasnecessary to extinguish other combustible gases or vapors may be estimated. For example, only 1 volume of carbon tetrachloride vapor per volume of ethylene dichloride vapor should be required to render such mixtures non-inflammable.
Per cent 4.0 3.0 3.1 3.0
5.0 5.8a 12.5
Higher
N
COz
CCh
by u01.
Vols. 10.5 15.3 12.8
Vols. 10.2 9.0 7.3 7.3 3.2 2.30 2.2
Vols.
74.0 28.0 12.6 80.0 15.0 15.9'L 74.0
....
0.0
....
4.1
... ... ... ...
1.4
...
...
These values at 100' C.
The limits of inflammability of combustible gases and vapors are widened somewhat by increased temperatures, so at the usual laboratory temperatures slightly less carbon dioxide than that given should be required to render ethylene non-inflammable at these lower temperatures. However, to provide a factor of safety, a t least 2.5 volumes of carbon dioxide should be mixed with each volume of ethylene dichloride to insure such mixtures being non-inflammable, or on a weight basis at least 1.25 pounds of carbon dioxide per pound of ethylene dichloride should be used. Conclusions
1-The limits of inflammability of ethylene dichloride-air mixtures at 100" C. and atmospheric pressure were found to be as follows: lower limit, 5.8 per cent; higher limit, 15.9 per cent. The lower limit a t laboratory temperatures (22' C.) was found to be 6.2 per cent. 2-Ethylene dichloride may be rendered non-inflammable by mixing 2.3 volumes or more of carbon dioxide with each volume of ethylene dichloride or, on a weight basis, 1.02 pounds of carbon dioxide per pound of ethylene dichloride. These values are for a temperature of 100" C. and atmospheric pressure. 3-For atmospheric temperatures slightly less carbon dioxide would be required; however, to ensure a factor of safety it is recommended that at least 2.5 volumes of carbon dioxide be added per volume of ethylene dichloride, or on a weight basis, a t least 1.25 pounds of carbon dioxide per pound of ethylene dichloride. Literature Cited (1) Cotton and Young, Proc. Entomol. SOC.Wash., 31, 97 (1929). (2) Jones and Klick, IND. END. CREld., 21, 791 (1929).
