VOL. 5, NO.3 NEWMETHOD POR DEMONSTRATING DUSTEXPLOSIONS
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A NEW METHOD FOR DEMONSTRATING DUST EXPLOSIONS RALPH
E. DUNBAR, DAKOTA WESLEYANUNIVEKSITY, MITCHELL,SOUTH DAKOTA
The author has used many of the traditional experiments, usually included in numerous texts and laboratory manuals, for the demonstration of the phenomena of rapid burning, oxidation and combustion, including dust explosions and spontaneous combustion. Among those frequently suggested is the use of yellow phosphorus dissolved in carbon disulfide. Also many combustible substances, such as wood charcoal, when heated to incandescence and poured into an open cylinder containing oxygen, burst into flame with almost explosive violence. These demonstrations undoubtedly have their advantages but in many cases the conditions under which the experiment is performed are more or less artificial. It has been the author's experience, through a period of years, that students frequently place the emphasis upon some incidental property of the chemical used rather than the central idea of the demonstration, unless their attention is specifically called to this fact. The piece of simple apparatus, illustrated here, employs no superficial conditions or substances. A tin can of one-half to one gallon capacity with removable cover is selected. A small opening is made in the bottom through which the stem of a small laboratory funnel may be dropped. A rnbber bulb, withvalves for pressure, is connected to the lower end of the funnel bv means of a rubber connection in such a manner that air can be forced through the funnel when desired. A small candle is then fastened to a suitable support so that it can be placed in the can or removed a t will. When the demonstration is to be performed, the funnel and bulb are arranged. A small amount of corn starch is placed in the funnel and the candle is lighted and lowered into place by means of suitable tongs. The cover is quickly placed in position and pressed down firmly. One or two puffs of air from the bulb through the funnel is usually sufficient to fill the can with cornstarch which causes an energetic explosion that throws the cover several feet into the air, but otherwise does not affect the apparatus. It will be noticed that the conditions here are identical with those frequently encountered in practical experience, ordmary air, an open flame,
and some finely divided combustible material. The use of cornstarch closely resembles conditions found in starch factories. Finely divided coal, flour, and other similar substances may be substituted for the cornstarch, thereby giving a wide range of similar possibilities.
