INCENDIARIES MARVIN ANTELMAN Yeshiva University, New York, New York
HERE are a few incendiary reactions to enliven lectures and to stimulate student interest. Spontaneous Combustion. Mix 75 ml. of turpentine with 75 ml. of Japan drier in a 250-1111, beaker, and to this add rags or cotton waste. Allow some time for the chemicals to soak. Using forceps carefully remove the mass and place it in an evaporating dish. Measure the temperature a t intervals. The temperature rises rapidly and will reach the kindling temperature in about 20 or 30 minutes. On no account should the treated rags or cotton wastes be touched with the hands. Unused material should be disposed in metal containers for obvious reasons. Combinations of Chemical Elements. The action of sulfur with metals is incendiary, e . g., ignition of zincsulfur mixtures. The final product is sometimes dissolved in dilute HCI to show students that H2S is evolved when sulfides are treated with acids. Equally spectacular is the substitution of aluminum for zinc. The sulfide of aluminum differs from its zinc counterpart inasmuch that it is soluble in water, reacting with it to liberate HzS. White phosphorus placed on iodine crystals takes fire spontaneously. Peesized bits of red or white phosphorus thrown into an evaporating dish containing a small quantity of bromine produce different effects, throwing up yellow flames as they touch the surface. Commonly used combinations of this type are the chlorine and oxygen combustions of metals and nonmetals. Reactions with Potassium Chlorate. The oxidizing effect of potassium chlorate is well illustrated by the socalled "Chemical Hotfoot." A 6 by 3/d-inch test tube is placed securely in the jaws of a buret clamp from which the rubber sleeves have been removed. Fill up to 3/4 inch from the rounded bottom portion of the test tube with KC103. Heat the tube until the chlorate forms a transparent melt. The clamp should now be screwed t.0 a ringstand. Drop a wooden splint into the melt. A tremendous npshoot of flame and smoke takes place. After the reaction subsides add another splint, and the reaction is revived. As many as ten splints may be added to this small amount of material, producing heat and light each time. The number of splints added a t a time may be varied. Sulfur-chlorate mixtures explode when hit with a hammer as do phosphorus-chlorate mixtures. It is unsafe to add sulfur or phosphorus to molten.KC103. Chlorine peroxide is a very unstable substance formed by the action of concentrated nitric or sulfuric acid on chlorates. Add a drop of concentrated H2SO4to a
little KC103 in an evaporating dish. The reaction is violent and spontaneous and may be accelerated by adding carbon, preferably in the form of sugar. There may be some spattering of acid if larger quantities are used. In the reaction chloric acid is liberated, which decomposes into chlorine peroxide as follows: Although magnesium burns brightly in air and more brightly when in contact with oxidizing agents or oxygen, an almost explosive reaction occurs if magnesium is ignited with KC103 by the means of electricity. To illustrate this, powdered Mg and KC1O3 are mixed (do not grind) in portions of one part by weight Mg to 1.7 of KC103. Place the mixture in a crucible containing a resistance wire connected in circuit to a suitable current source controlled by a switch. It is s-good idea to keep at a safe distance, extending the circuit as far as possible. When the switch is released the reaction will proceed instantly. Glycerol-Permanganate Reaction. If potassium permanganate and glycerol are mixed to a thick paste, smoke is given off and combustion finally takes place. With 0.2 ml. glycerol mixed with one gram of permanganate fire occurs within 20 seconds. This reaction illustrates the oxidizing action of potassium permanganate according to the following equation: CROH
I
YHOH I
0
CH,OH Glycerol
CHIOH
I
YHOH I
COOH
0
I
+YHOH (+2H,O)
COOH Glycerio acid
I
COOK Tartronic acid
Water Added to Mixtures. Mix i o d i e with equal amounts of Al, Mg, or Zn in three separate piles, and add a drop of water to each. Ignition occurs, and violet i o d i e vapors are given off. The heats of formation for magnesium, aluminum, and zinc iodides are 84,800, 70,300, and 49,231 calories, respectively. The place of these metals in the electromotive series is easily noticed by the vigor with which the combinations take place. Water will also ignite a mixture of 500 mg. of zinc dust, 500 mg. of ammonium nitrate, and 200 mg. of ammonium chloride. Larger amounts can be used in the same proportions if desired. The reaction proceeds instantly after a drop or two of water is added. The mass smokes and then burns. Ammonia odors may be detected in the smoke. Hydrogen P e r o d e with MnOz. Place a little MnOl in an evaporating dish, and allow a few drops of 30 per
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MARCH, 1953
cent hydrogen peroxide to fall upon the powder from a iodide, is very convenient to prepare and exhibits the height of six inches or more. As each drop makes con- same explosive properties. To prepare NCI,, fill a one-liter flask with chlorine tact with the MnOz, the H20zdecomposes with a small explosion, releasing oxygen, and vaporizing the water gas (use a long necked flask if possible) and immerse the present in dilute HzOz as a cloud of steam. Exercise neck in a basin containing a saturated solution of caution when handling 30 per cent H202as it attacks the ammonium chloride. Place a lead evaporating dish below the mouth of the flask. As the chlorineisadsorbed skin like concentrated acids. the solution will rise into the flask. When the flask is Small quantities of Zinc and Sodium Hydroxide. zinc added to a dilute sodium hydroxide solution re- ahout three quarters full, NCls will form on the sides and lease hydrogen; but if the proportions of the reactants fall into the dish. By transferring the dish from the are varied considerably, totally different effects will solution with clean tongs the chloride may be exploded result. Dissolve 10 g. of NaOH (flakes or pellets) in by tickling it with a feather attached to a long glass rod. 95 ml. of water. Add powdered zinc until a thick paste The chloride may be prepared by other methods, one of forms. Squeeze the paste between sheets of absorbent which is the electrolysis of a concentrated solution of paper to remove excess moisture. Spread the paste NHICI, the chloride being liberated a t the anode. on an ashestos board (or other fireproof nonconducting Chlorine reacts with NH&l as follows: surface) in order to form a layer inch thick. Com3C1,.+ . NHLCI- NCl.. . 4HC1 bustion takes place a t the end of two minutes. Three When iodine crystals are dissolved in a solution of chemical reactions are involved here. ( a ) Zinc reacts potassium iodide and the solution added to concentrated with NaOH, (b) zinc is oxidized to its oxide by atmosNH40H, a precipitate forms. This red-brown precipipheric oxygen, and (c) zinc oxide reacts with sodium tate is a nitrogen azoimide. I t will not explode when hydroxide when moist. These three reactions acwet but when dried it explodes when tickled with a cumulate sufficient heat to lead to combustion. feather. The formation and explosion of the subVolcanic Effects. Ammonium dichromate ail1 destance are expressed by the following equations: compose into green chromic oxide (CrzOa)known com6NHs + 3 4 2NHa. ??Ia + 3NHd mercially as "chrome green." If a quantity of the di311 4NHa N* 2[2NHs. NIal chromate crystals are placed in the form of a mound and Charcoal Rurning with Absorbed Gases. One can ignited, a volcanic effect is observed. Green bits of Cr203and sparks are thrown into the air. At the end of strikingly demonstrate the ability of charcoal to absorb the reaction, the green oxide, which is lighter than the gases in the following manner. Fill a gas-collecting dichromate, is left in a pile much larger than the origi- bottle with HzS and two others with Oz. Fill two denal. Decomposition of (NH4)&Or is expressed by the flagrating spoons with charcoal, and place one in the bottle containing H,S. Simultaneously ignite the confollon-ing equation: tents of both spoons, and immerse them in the two bot(NH,),CROI N3 4H2O ChOs tles of oxygen. I t can readily be seen that the charcoal Goldschmidt Reactions. Chromium is manufactured containing the H2S burns the most brightly. P p p h o r i c Substances. Certain substances are by the reduction of CrzOausing A1 as the reducing agent in the Goldschmidt process. This process may be known as pyrophoric compounds or mixtures. If upon simulated on a smaller scale. Fill a crucible z/3 full of a being heated in a test tube and their' contents thrown mixture of powdered Al and Cr203. Place the crucible out after heating, they catch fire. Some organic lead in a dish or pail of sand. On top of the A1 and Cr203 compounds have this tendency. To illustrate this, try mixture place a mixture of powdered magnesium and using lead oxalate, citrate, or tartrate. Lead chromate sodium peroxide. Now insert a piece of magnesium in and sulfur, alum and brown sugar, potassium sulfate the center and ignite it. Keep a t least six feet away and carbon, alum and flour, are all pyrophoric mixtures. after lighting the magnesium. The ribbon burns down- The term pyrophoric is also applied to alloys such as ward igniting the peroxide mixture. This in turn ig- misch metal and Auer metal, which emit sparks when nites the aluminum, causing it to burn mith almost ex- scraped or struck. Substances Producing Volumimus Ash. Some suhplosive violence. Due to the nature of this reaction the crucible is liable to break. Metallic chromium is stances when heated leave a voluminous residue beh'md. formed. In the thermite reaction oxides of iron are Mercuric thiocyanate, sold as a novelty, or a mixture of potassium dichromate, nitrate, and sugar give this substituted for chromic oxide. Nitrogen Halides. The chloride and iodide of nitro- effect. For lecture purposes p-nitroacetanilide gives gen are interesting substances. Dulong, who discov- much better results. Place some of this yellow powder ered the chloride in 1811,lost one eye and three fingers in in an evaporating dish and moisten it mith concentrated the process. Both substances are very unstable, being H2S04until a thick paste isformed. When thisis heated subject to explosion a t the slightest touch. They can on a ringstand over. a Bunsen Burner, such a large he prepared and safely exploded under proper condition. quantity of ash is produced that it mill climb out of the Nitrogen chloride (NCI,) is a yellow oil. The iodide dish onto the base of the ringstand and creep along the (N13 is in reality a black solid. A red-brown lecture table. The circumference of this ash is equal to iodoazoimide (2NH8.N13), commonly called nit,rogen that of the evaporating dish.
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