The Thermite Reaction: A Chemical ~roun'd Breaking A few years ago we opened a new engineering building and, as part of the ground-breaking ceremony, some fireworks were activated with a laser. Late last summer we got permission from the State of Michigan to begin construction on a new building complex which includes a science building. I remarked that the chemists ought to be able to outdo the engineers when it comes to having a spectacular ground-breaking ceremony. That intemperate remark, plus a decided inability to say no at crucial moments, led to my appointment as chairman of the ground-breaking committee. Although I had to eoordinate the entire event, my main job was to devise an unusual ground-breakingprocess. After several false starts, I hit upon using a large thermite reaction to "break the ground." I felt that the thermite, ejecting its fiery ball of iron into the ground, would make a very gwd show. The main problem, ss I saw it, was to figure out how to set the thermite off at a safe distance. I was quite familiar with the reaction, as I N n it several times a year for classroom demonstrations, science open-house shows, etc. Those are always small reactions, done in a crucible, and ignited by dropping glycerine on powdered potassium permanganate. Searching and a fairly extensive chemistry demonstration file) unearthed the literature available to me (back issues of THIS JOURNAL no references to remotely detonated thermite reactions. However, with same thought and experimentation, I devised an extremely simple and reliable method. Into the container of thermite I buried a few strike-anywherekitchen matches, with heads up and level with the surface of the thermite mixture 131 FezOaIpowdered Al, wt%). Around those matches I placed a loop of 20 gauge Nichrame wire, leading the ends of the wire out of the container. Those were attached to a simple18 gauge lamp cord wire which was plugged into a Variac. Setting the Variac on about 50 and turning the switch on caused the Nichrome wire to glow and ignite the matches. That set off the themite. In the process of testing the method, I sealed it up from a 00-sized crucible, with one match, to the fmal-sized 12-in.-diameterflower pot with 14 pounds of thermite mixtwe and about 20 matches. It never failed. I used a Variac with a circuit breaker, rather than a fuse, so I did not have to replace the fuse each time. The method did not require any of the usual starter mixtures, such as BaOz or KMnOl. The day ofthe groundbreakingsaw our fmt winter storm blow through, giving conditions far from ideal. The temperature was 30°F, there was about two inches of fallen snow, and a 25 mph wind. In spite of those adverse factors, the themite went off beautifully. I should note that I cheated on the "ground breaking." I supported the pot on a ring about four feet from the ground and, directly under the pot, I had dug a small hole. In the hale were placed several tubes of dass C fweworks and, sprinkled on top of those, a mixture of sugar, potassium chlorate, and strontium nitrate. At the signal, I threw the Variac switch. There was a short delay as the wire heated, and then the thermite ignited in a spectacular display. The ball of iron was ejected from the bottom of the pot and immediately afterwards the pot shattered from the intensity of the reaction. Everyone agreed that it was a great show. One word of caution. The thermite, plus the mixture on the ground, caused a huge cloud of smoke to be released. The wind drove that cloud directly into the tent provided for the speech makers. Try to arrange the process so nothing of importance (especially state legislators) is downwind.
George W. Eastland, Jr. Saginaw Valley State College 2250 Pierce Road University Canter, MI 48710
Volume 61
Number 8
August 1984
723
