FLAMMABLE SOLVENTSTHEIR PROPERTIES A Lecture before Beginning Work in the Organic or Asphalt Testing Laboratory
AUGUSTUS H. GILL Massachusetts Institute of Technology, Cambridge, Massachusetts
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HE WRITER has been giving instruction for smoke these by attaching them by a rubber holder many years in the analysis of road m a t e r i a l s and tubing to the suction pipe. The ashes can be asphalts, tars, and oils-involving the use of 86" knocked off into the gasolme to give a glowing, ungasoline and carbon bisulfide. This is probably one covered end. In these four experiments the Merent of the most dangerous of instruction laboratories, for substances will all cease to burn, as the air is excluded in the usual organic laboratory the volatile liquids by the excess of gasoline vapor. are mostly confined in flasks or separatory funnels, Molten solder can be dropped into gasoline without whereas filtration of solutions of the above solvents harm, and the liquid can even be stirred with the hot is involved in the road materials analysis. To familiar- soldering copper itself. The danger in soldering comes ize the student with some properties of these solvents from the match flame used to light the torch or from a preliminary lecture is given upon the behavior of the torch itself. So in the case of smoking, the match these and other solvents. . flame causes the ignition and not the glowing tobacco Attention is called to the fact that the vapors are (though flame-bearing tobacco will do so). Gasoline all heavier than air, and sink therein as does a stone may even be stirred with a '/a-inch iron rod heated to in water. This is shown by actually pouring 86' a dull red, but look out for white heat! To ignite 8F0 gasoline vapor, not the liquid, from one beaker into gasoline a cherry red or white heat is necessary (above another and setting fue to the vapor in the latter. 780°C.) or the flame of a pine splinter or an electric These vapors flow just like liquids. This is shown by spark. using a twelve-foot length of four-inch galvanized To demonstrate the flammability of the vapor, iron gutter with one end elevated 2 feet above the remove the funnel from the beaker and insert the other, which ends a t a short, lighted candle. When flaming splinter; the flames, which-mount to a height 5 cc. of 86' gasoline is poured into the top of the of several feet, are readily extinguished by the funnel, gutter it flows about half way down as a liquid, con- the thumb closing the stem. tinuing as vapor, to ignite from the candle and flash For electrical ignition, make a device whereby a spark back to the top of the gutter. This illustrates the can be passed between wires supported on a bent glass specific gravity and volatility of the gasoline and rod which can be dipped into the liquid gasoline the fact that i t always flashes haek to its source. and then gradually withdrawn. Loker the sparker Cases are on record in which vapor has gashed hack almost to the surface of the liquid, then make the spark, sixty feet, setting fue to the oil storage whence it dipping it into the gasoline itself and gradually withdrawing it; the gasoline vapor will take fire about came. A further illustration is furnished by a recorded three inches from the liquid surface. The spark does automobile fire. Wbile the rear tank was being med, not set fire to the vapor immediately over the gasoline mixture is too rich. This illusthe owner lighted a cigaret a t the front of the car. for lack of &-the The breeze carried the gasoline vapor the length of the trates the necessity of the correct amount of aif. The foregoing lecture demonstrations are supplecar where the vapor stratum was ignited. For the production of a flame, two conditions are mented by the following experiments which show the necessary--a sufficiently high temperature to ignite relative inflammability of the solvents. Apparatus needed: No. 7 porcelain crucible, 4-inch the vapors, and the proper mixture of air and combustible vapors. To demonstrate the first, put about funnel, lamp, thermometer, matches, and, if wooden500 cc. of 86' gasoline into a tall (about 12-inch) topped desks are used, a sheet of asbestos or transite 6-liter beaker. Cover it with an 8-inch glass funnel 6 inches square. Experiment 1. Fi the crucible one-third full of to serve as an extinguisher. Remove the funnel after a few minutes and insert a long, glowing splmter of carbon bisulfide, heat the thermometer to 250°C., northern pine wood into the vapor. It will not inflame and bring i t h e r the mcible. Extinguish the ensuing if care be taken that the splinter is only glowing, i. e., flame with the 4-inch funnel holdmg the thumb over with no small flames on it. Try similarly an actively the stem. Exfieriment 2. Repeat Expt. 1 using 86' gasoline smoked pipe, cigai, or cigaret. It is advisable to 4!55
and employing a match to ignite the vapor; extinguish as before. Ex$eriment 3. Repeat Expt. 2 using benzol. Ihfieriment 4. Repeat Expt. 2 using chloroform (showing that a volatile liquid is not necessarily inflammable). The ease with which these various liquids are ignited is to be carefully noted and remembered; every flammable substance has its kindling point, as every politician is said to have his price. This brings us to the directions for laboratory work. On account of the sticky nature of the materials handled, it is absolutely necessary for the student to provide himself with a long laboratory coat, and wear it a t all times in the laboratory. For a similar reason, and also on account of the fire risk, books, slide-rules, etc., should be kept in the desk drawer and not exposed on the desk top. Two mles if followed will diminish fire danger: (1) Never open a bottle of inflammable liquid, or handle an open vessel containing such liquid, without first looking to see where the lighted gas burners are, and avoiding them. (2) Never light a match without seeing 'if there be inflammable liquids in open dishes or bottles in the immediate neighborhood, and removing them. In handling these liquids it should be remembered that the vapors of them all are much heavier than air (about three times as heavy) and flow like a stream of water; they can be poured from one vessel into another. Consequently, they may flow several feet along the top of a desk to a flame. Gas burners should be lighted only when needed and extinguished as soon as possible. EXTINGUISHING FIRES
If a fire occurs, it should be handled promptly and without panic. See that all gas jets are turned out and all idammables removed to a safe distance. The fire is to be fought by excluding a g a n d absorbing the liquid in sand or sawdust.' The use of water is not advised for two reasons: the burning liquids float upon it, and the damage due to water may exceed that due to fire. The chemical fire extinguisher, by which &hefire is smothered with foam andcarbonated water, as with a blanket, is excellent. A liquid burning in an open dish may be extinguished by clapping on a cover of asbestos board or a folded wet towel. Where complicated apparatus takes fire, it is to be covered with an asbestos or woolen blanket, laboratory coats, or damp towels. Clothing on fire is to be similarly treated. Under no circumstances should the person
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Bmnmn. Eng. News. 69,217 (1917).
Students should learn the position of sand pails, extinguishers, and blankets, and if a lire occurs, an instructor should be notified a t once. He will take charge of the volunteer fire brigade. In cleaning apparatus, water is not to be used except for removal of dust or water-soluble salts; bituminous materials are best removed with solvents such as benzol or carbon tetrachloride. These are better than carbon bisulfide, which, on account of its ready inflammability and poisonous character, is to be used just as little as possible. The inhalation of its vapors is to be specially avoided. Oils, tars, etc., are to be wiped up or absorbed with cotton waste, kept in galvanized iron cans, and when used it is to be put immediately into the special waste can. Bits of cotton waste left lying about or thrown into waste jars increase the fire risk. Similarly, all oils, solvents, etc., must be poured into the receptacles provided and on no account into the sinks. In the twenty years that instruction has been given in road materials we have never had a fire, thanks to the observance of these precautions and rules: the present class does not want to be the exception and "start thmgs." One fire and one only was caused by the unexpected and sudden breaking of the 500-cc. retort in which a Tarvia B was distilled, emphasizing the need of a laboratory coat. It may be helpful to include the directions for keeping the notebook. DIRECTIONS FOR KEEPING NOTEBOOKS
1. 2. 3. 4. 5. 6.
Make a heading for each page. Date your work and write up your diary every day. Index each new subject. .. . ' Leave 4 pages a t front for an index. Leave 6 pages at end for a diary. Enclose Dercentaee of constituent found in a freehand rectangle thus: % SO3 = 1.42 Leave one line beneath it. 7. Cite references consulted, e. g.,' Allen: Org. Analysis, 3rd ed. (1899), . . Vol. 11, Pt. 1, p. 276. Smith: J. SOG.Chem. Ind.,24, 234 (1905). 8. Do not write uoon the last two lines or within ' ,/ A. inch of the e&e of the Dace.
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Some may object to these instructions as being "too &t and dried." The arrangement is time-saving to the instructor, and in after life invaluable to the future employer. He wants to know where in the notebook the work is to be found, when it was done, perhaps the time it required, what was done and how, and finally the results obtained. In a notebook kept according to this scheme all these things can be determined almost a t a glance. Contrast~thiswith the hodge-podge one sometimes finds.
