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INDUSTRIAL AND ENGINEERING CHEMISTRY
diameter copper nozzle. The hydrogen and et,hane used were commercially pure materials. The 99.4% diborane used was not spontaneously flammable, hence it xas lighted with an ordinary laboratory sparker. Black deposits forming around the diborane flame nozzle had to be removed occasionally t o prevent plugging. In a few cases of inadvertent plugging the pressure buildup eventually forcibly ejected the plug with the formation of disconcertingly large flames. Safety precautions were of course necessary to provide for the surprise flames and explosions usually attenda n t upon handling diborane in air near flames and heated surfaces. Carbon Dioxide. Insertion of a diborane flame into a carbon dioxide atmosphere-generated by a l l o v h g dry ice to stand in a beaker a t room temperature-simply resulted in lifting the flame from the flame nozzle t o the carbon dioxide-air interface, where the diborane continued t,o burn with a beautiful pale blue flame. Under similar conditions both hydrogen and ethane flames were quickly snuffed out. A stream of carbon dioxide from a bIodel 2 l / 2 T Kidde extinguisher had little effect on a diborane flame 1 foot away, but at a distance of 3 inches the flame was put out. Reignition occurred unless the flow of carbon dioxide was continued long enough t o allow the metal nozzle t o cool. Short bursts from the same fire extinguisher quickly snuffed out hydrogen and ethane flames 1 foot away, and there was no reignition. Carbon Tetrachloride. When a diborane flame was placed in a n atmosphere of carbon tetrachloride-generated by refluxing this compound in a beaker-the diborane continued to react for an extended period with formation of dense black smoke. Under similar conditions a hydrogen flame also continued to react, but an ethane flame was instantly snuffed out. \Then diborane was burned in a mixture of air and carbon tet'rachloride vapor, the odors of hydrogen chloride and phosgene were detected. Sand. A diborane flame which had been burning for 10 seconds vias extinguished when 400 ml. of ordinary dry sand was piled over it all at once. Removal of the flame nozzle from the sand pile after 10 seconds gave no reignition of the still floiTing gas. In one instance reignition did occur when the flame nozzle was removed from the sand pile after 5 seconds. When 400 ml. of ordinary dry sand was piled slowly on the flame, the diborane continued to burn on the surface of the sand pile; however, the blue flame went out, when the height of the pile above the flame nozzle reached about 1 inch. After the flame was extinguished, sparking the sand pile lvith diborane still flowing gave repeated explosions. Insertion of a diborane flame into a falling stream of ordinary dry sand did not extinguish the fire. R e t sand seemed t o be less effective than ordinary dry sand for putting out diborane fires. The agglomerating effect of the vater on the sand tended t o leave continuous crevices through which the diborarie continued to burn. Sodium Bicarbonate. Pox-dered sodium bicarbonate acted much like dry sand when piled over a diborane flame. Diborane continued to burn on the surface of poivdered sodium bicarbonate layered t o a height of l/*inch over the flame nozzle. Nitrogen. A jet of diborane burning a t the end of 3/8-inch glass tubing was inserted 3 inches inside of a 1-inch glass tube carrying a nitrogen gas stream flowing countercurrently. This resulted simply in transferring the cliborane flame from the tip of the smaller tube t o that of the larger tube, where combustion continued. A diborane flame continued t o burn for 20 seconds when held either just above or just below t'he surface of commercial liquid nitrogen. Under both these conditions hydrogen and ethane flames were quickly extinguished. A flame may propagate itself along a tube of static diborane. When gas flow was shut off t o a flame a t the end of an 8-inch length of 3/8-inch glass tubing, the flame worked its way back a n inch into the tube in a few minutes. At this point because the flame was apparently out, the tube was set aside. Shortly
Vol. 46, No. 8
thereafter there was a sharp explosion which shattered the end of the glass tube. Steam. A jet of stream from .a l/a-inch nozzle extinguished R diborane flame only Q-henthe steam jet "as directed on the flame nozzle from a distance of a few inches. An atmosphere of steam generated by directing a steam jet into a small beaker was ineffective against a diborane flame. Water. Pouring water over a diboranc flame quickly put it out, and there was no reignition when the water flow was stopped, Insertion of the flame nozzle beneath the surface of water also resulted in extinguishing the flame with no reignition when the nozzle was exposed to the atmosphere wit,h diborane still flowing. 4 shower from a disk having 50-mil holes was quickly effective against a diborane flame, and there m-as no reignition when the vater f l o was ~ stopped. CONCLUSIOKS
On the basis of qualitative Iaborat'ory scale experiment,s, it was concluded that: 1. Burning diborane gas is considerably more difficult t o extinguish than are ordinary burning gases, such as hydrogen and ethane, and the danger from explosive self-reignition is greater. 2. Carbon tetrachloride must never be used on a boron hydride fire. 3. Diborane can continue t'o burn in much lower conccnt,rations of oxygen than can ordinary gases, hence larger and more concentrated quant'ities of effective fire extinguishing agents must be used. 4. Burning diborane gas escaping from a closed fiyst,ernis most. effectively combatted with copious quant,ities of water continuously applied in order to hydrolyze the escaping gas and t,hcrchy prevent explosive self-reignition. The reactivity of boron hydrides with water makea it necessary to apply this fire extinguishing agent very judiciously. The heat of hydrolysis of diborano is very considerable, and one of the products of the reaction is hydrogen, which of course is a potentially explosive hazard. Circumstances can readily be conceived-e.g., a fire in a vemel of liquid or solid boron hydride-in which water is absolutely contraindicated. I n such cases recourse must be had t o ot'her agents, such as carbon dioxide. The results of this investigation provide a basis for ticvi~ing effective fire-fighting procedures for other boron hydrides, such as liquid pentaborane (BJ19) and solid decaborane (BloH14). ACKNOWLEDCXIEKT
The author is grateful for advice and assistance from A . E. Xeiykirk and L. V. YIcCarty with whom he has coilaboratcd in boron hydride inveetigatioris. LITERATURE CITED
(1) LIcCarty, L. V., and
George, P. D., J . A m . Chenz. Soc.. 73 31:iIi
(1951).
Price, F.P., Ibid., 72, 5361 (1950). (3) Whatley, A . T., and Pease, R . N., I t ~ i d . ,76, 1997 (1954). ('2)
RECEIVED for review October 2Y, 1953.
ACCEPTEDApril 1 ,
1064.
Activation of Carbon--@orrection I n the article by W.K. Lewis and 8.B. Metzner [IND.ENQ. CHEM.,46, 849 (1954)], the t,hird sentence on page 851 should read: This increase in reaction rate was approximately equal t o the increase in the partial pressure of diatomic sulfur (&I in the gases. At the top of page 852, the third line should also include the designation, diatomic sulfur (SI).
