INDUSTRIAL AND ENGI,YEERING CHEMISTRY
146
larly prepared and are unusual products in their properties and because they contain no caustic alkalies. Emulsification of Solvents
A number of water emulsions of industrially important solvents have been satisfactorily prepared with triethanolamine. The usual method of emulsification does not yield so spontaneous an emulsion as is obtained with liquid fats, and thorough agitation is required in every case. The products, however, are permanently stable in the concentrated form and their storage or marketing as such is feasible. There are various uses for emulsions of these solvents as polishes, disinfectants, sprays, and cleaning compounds. There is a distinct advantage in using triethanolamine in automobile and lacquer polishes, for it has been found that neither the free base nor its soaps has any injurious effect on lacquer finishes. A mixture of kerosene, o-dichlorobenzene, and turpentine has been successfully emulsified in water with triethanolamine and oleic acid in the presence of dyes, oils, and inert abrasives such as rouge, tripoli, and precipitated chalk to give a very satisfactory metal cleaner and polish. As a scouring compound a mixture of 60 per cent triethanolamine oleate with 40 per cent ethylene dichloride has been found readily emulsified with water to give a solution combining good detergent and solvent action for use with textiles. The kerosene emulsion is especially interesting as a tree-
VOl. 22, KO.2
spraying material. It may be made in a very stable form with a concentration of kerosene up to 85 per cent of the oil by volume and readily dilutable with water, in this respect, a t least, being far superior to the usual orchard sprays. I n connection with this emulsion, or with a heavier soluble oil used for the same purpose, triethanolamine presents the additional advantage of low alkalinity which should cut down much of the "burning" of foliage encountered after sprayings. The wetting properties of the emulsion due to the low surface tension make them especially suited for accomplishing a uniform coverage of foliage and a satisfactory impregnation of scale insects. Further emulsions which have been made with triethanolamine confirm its general utility in this field. A number of edible oils, such as olive, castor, and refined mineral oils, the palatability of which is greatly increased by emulsification, are readily emulsified with this base, although they may not be recommended for internal use until the physiological inertness of triethanolamine has been confirmed. I n conjunction with colloid-mill dispersions, it is interesting to note that triethanolamine oleate has been found one of the most efficient of the available emulsification colloids, less than 5 per cent of the soap being sufficient to keep most emulsions in their finely divided state indefinitely, and in some cases as little as 1 per cent of the base is able to stabilize the emulsions of an oil of some natural free-acid content.
Extinction of Ethylene Oxide Flames with Carbon Dioxide' G. W. Jones and R. E. Kennedy PITTSBURGH EXPERIMENT STATION, U. S.BUREAU OF MINES,PITTSBURGH, PA.
URING the past few years several new compounds
D
have been introduced as fumigants. Among these, ethylene oxide, C2H40,has perhaps received the most attention. Cotton and Roark (1) were the first to study the use of this compound as an insecticide. At about the same time Hoyt (3) published an article on the comparative toxicity of ethylene oxide and other fumigants. These results showed that it required 2 pounds of ethylene oxide for 1000 cubic feet of air, making a 24-hour exposure a t 75-80' F., to give a 100 per cent kill of all the insects used in the test. These included larvae of the clothes moth, larvae of the Indian meal moth, and adult flour beetles. On this basis the calculated percentage by volume of ethylene oxide present in the mixture equals about 1.8 per cent. Ethylene oxide is a combustible gas and its extensive use as a fumigant introduces certain hazards due to possibilities of explosions, especially when used in fumigating large volumes -for example, in grain elevators-in which great damage might result should an explosion occur during fumigation. For the above reasons an investigation was conducted to determine the limits of inflammability of this gas in air and means of reducing these limits by the addition of carbon dioxide. The ethylene oxide tested was supplied by the Carbide and Carbon Chemicals Corporation in small iron tanks. It was used as received after a few cubic feet had been allowed to escape from the tank to remove the permanent gases which might be present. Ethylene oxide as received in tanks is a liquid which boils a t 10.5' C. At the usual laboratory tem1 Received December 3, 1929. Published by permission of the Director, U. S.Bureau of Mines. (hTot subject to copyright.)
perature, 22" C., it is a gas. It is soluble in water in all proportions. For this reason the usual procedure of determining the limits of inflammability could not be followed. Apparatus for Testing Inflammability
With certain modifications, as shown in Figure 1, the standard apparatus for determining the limits of inflammability of gases was used in these tests (4). The partial-pressure method was used for preparing the test mixtures-that is, the explosion tube was completely evacuated by the Hi-Vac pump and the tube closed off a t stopcock b, and the height of the mercury column in the manometer attached to the explosion tube was read to the nearest 0.5 mm. The desired amount of ethylene oxide was then added direct to the explosion tube through cock a. For example, if 5 per cent of ethylene oxide was desired and the height of the mercury column after evacuation was 745 mm., then 746 X 0.05 = 37.2 mm. Ethylene oxide was admitted to the tube by slightly opening stopcock a, thus allowing the gas to enter. When the mercury column in the manometer had fallen 37.2 mm., cock a was closed and the mercury column read carefully. After 2 minutes the manometer was read again as a check and to determine whether there were any leaks in the apparatus. Kext, air was added through cock b and the calcium chloride drying tube slowly until the mixture in the explosion tube was at atmospheric pressure. Cock a was then closed and the gases were mixed by means of a magnet c and the light iron deflector, d. Before the explosion tube was filled with the gas mixture, the deflector was drawn to the top of the tube and held there by the magnet. To mix the gases the magnet
February, 1930
INDUSTRIAL A N D ENGINEERING CHEMISTRY
yellow-orange color, and a large quantity of very fine carbon is deposited. Effect of Carbon Dioxide on Inflammability In view of the wide inflammability limits of ethylene oxide in air mixtures, tests were made to determine how much carbon dioxide must be added to these mixtures to render them non-inflammable. Carbon dioxide has a twofold value: It reduces the explosibility of the ethylene oxide mixtures; and it has been shown by Cotton and Young ( 2 ) that it stimulates the respiratory processes of the vermin, which it is desired to destroy-that is, they absorb the ethylene oxide a t a faster rate and are more quickly killed. The area of inflammability of ethylene oxide, carbon dioxide, and air mixtures is shown graphically in Figure 2. This shows that carbon dioxide has a marked extinctive effect on the upper-limit mixtures over the range of zero to 2 volumes of carbon dioxide to 1 volume of ethylene oxide. When these proportions are above 2 to 1,the extinctive effect is more nearly normal and the slope of the curve in general agrees with those of other gases, such as methane and ethylene.
I/
tower
Figure 1-Flame-Propagation
147
pump
Apparatus
was drawn slowly up and down the outside of the tube from one end to the other. This procedure caused the deflector to follow the magnet on the inside. Experience showed that fifteen or more passes up and down the tube mixed the gases thoroughly. Tests for explosibility were run in the usual manner. If flame failed to propagate from the bottom to the top, the mixture was withdrawn from the tube through a charcoal filter. connected to a water filter-pump, and the tube aired in this manner for 15 minutes. Although the Hi-Vac pump was protected by a charcoal tower to prevent the vapors from getting into the oil in the pump, unless this procedure wac followed, it became necessary to change the charcoal filter after ten or twelve tests. I n the succeeding tests the proportion of ethylene oxide was increased in small increments until the mixture when tested propagated flame from the bottom to the top of the tube. The average percentage of the mixtures which just propagated and just failed to propagate was taken as the limit of inflammability. The same procedure was used in determining the upper limit of inflammability. Wide Limits of Inflammability
The lower and upper limits of inflammability (of ethylene oxide with air (roughly dried with calcium chloride) were 3 and 80 per cent by volume. From these results it is seen that ethylene oxide has wide inflammable limits. The1 are nearly the same values as those for acetylene in air (2.5 to 80.0 per cent). The upper-limit mixtures of ethylene oxide in air differ from those of acetylene in air, in that in the former, when the mixtures were ignited, there was considerable burning a t the bottom of the tube momentarily, and then, after a short interval, a pale blue flame propagated slowly from the burning mixture a t the bottom to the top of the tube. I n the case of acetylene in air the flames are highly luminous with a bright
VOLLMES OF CARBOY DIOXIDE PER VOLUME OF ETH'I LENE OXlDE
Figure 2-Extinction of Ethylene Oxide Flames b y Carbon Dioxide
It is seen that to render ethylene oxide-air mixture noninflammable under all conditions, a t normal temperatures and pressures, a t least 7.15 volumes of carbon dioxide per volume of ethylene oxide are required. As the molecular weight ot ethylene oxide and carbon dioxide are practically the same, 7.15 pounds or more of carbon dioxide should be added to each pound of ethylene oxide t o render it non-inflammable when mixed with air, and to insure a factor of safety it is recomniended that a t least 7.5 pounds should be used where large volumes are to be fumigated, as in grain elevators, and \%-here it is imperative from the standpoint of safety that a strictly non-inflammable mixture be used. Literature Cited (1) Cotton and Roark, I K DEKG CHEM 20, 805 (1928) (2) Cotton and Young, P/oc Entomol Soc Washington, 31, 97 (1929) (3) Hoyt, I h D E ~ CHEM G , 20, 835 (1928) ( 4 ) Jones and Perrott, I b i d , 19, 986 (1927)
