Thermite synthesis is a relatively simple chemical procedure, but one that requires particular attention to safety. Thermite is a combination of aluminium and a metal oxide, commonly some form of iron oxide, that burns at a very high temperature, even in the absence of an oxygen source. Iron (III) oxide, such as traditional rust, magnetite or even hematite, is typically used in the reaction. Contents [hide] 1 Warning and disclaimers 2 Procedure 2.1 Collection of Powdered Aluminum 2.1.1 Filing 2.1.2 Crushing Foil 2.1.3 Paint Stores 2.1.4 Etch-A-Sketch 2.2 Collection of Iron Oxide 2.2.1 Beach Sand 2.2.2 Electrolysis with Iron Anode 2.2.3 Electrolysis with Iron Anode 2 2.2.4 Hardware Store and Steel Wool 2.3 Mixing the Iron Oxide and Aluminium 2.4 Ignition [edit] Warning and disclaimers Thermite is impossible to control or contain once lit. USE EXTREME CAUTION. WATER WILL NOT EXTINGUISH A THERMITE REACTION. IT WILL CAUSE A STEAM EXPLOSION AND POSSIBLE PERSONAL INJURY. The same applies to almost all other liquids - they simply cannot draw heat away from the reaction as quickly as it is produced, and the oxidizer is already present so they cannot smother it. This article exists for informative purposes only; however, this information is in no way guaranteed to be correct. These procedures should only be performed by persons with appropriate training in chemistry. Accidentally igniting a thermite reaction could result in injury, death, or destruction of property. As such, it is to be suggested that the thermite and the igniter (e.g. magnesium ribbon) be stored separately until ready for use. DO NOT ATTEMPT if you are unsure of what you are doing or do not have access to proper facilities! See also: Wikipedia:General disclaimer. [edit] Procedure [edit] Collection of Powdered Aluminum [edit] Filing A labour intensive method is to file an aluminum block. A rough file must be used to prevent excessive packing of the file teeth. It is not safe to use a bench grinder that has been or will be used to grind iron or steel since there is a strong probability that a spontaneous, uncontrolled thermite reaction will occur. [edit] Crushing Foil A poor quality aluminum powder can be made by passing aluminum foil in a coffee grinder. A grinder using burr will acheive better results than grinder using blades. Small aluminum particles will contaminate the grinder so extreme care must be used in the cleaning before is it used for coffee again. [edit] Paint Stores Automotive paint stores and artist supply stores carry high quality aluminum powder that is used for metalic effect in paint. [edit] Etch-A-Sketch The display of an Etch-A-Sketch is filled with fine aluminum powder. [edit] Collection of Iron Oxide [edit] Beach Sand Magnetite is one usable form of Iron Oxide for this reaction. It is easily collected by passing a strong magnet into beach sand. Magnetite is the black powder that sticks to the magnet. [edit] Electrolysis with Iron Anode Cut the output (smaller, round) plug off of a typical AC adapter that provides a DC output. Separate the two wires in the cord and strip each of them, exposing about 2 inches of wire. Fill the glass jar with warm water. Add the salt and stir until the salt has dissolved. The salt allows the water to conduct electricity. Place the unwrapped ends of the two wires into the water, not touching each other. Plug in the AC-adapter. There is a risk of shock, even though the AC-adapters generally uses 6-12 volts, they can have high current. One of the two wires will start to bubble more than the other. This is the negative wire (-). What is occurring with the two wires in the salt water is water electrolysis. In this reaction ( 2H20 -> 2H2 + 02) water yields hydrogen gas and oxygen gas. The hydrogen gas forms at the cathode (Water Electrolysis experiment), and because 2 molecules of hydrogen gas are formed for every molecule of oxygen gas, this wire will bubble more. It is a good idea to mark this somehow so as not to forget; if the wires were to be reversed later, the end result would be rust acid instead of rust, which won't be very helpful. Wrap the positive wire around the large iron nail. Drop the nail into the jar, not touching the submerged negative wire. Attaching the nail to the cathode ( (-) wire ) only results in the oxide formation on the copper wire. Now, leave this as is for about 10 hours. A good amount of rust should form on the surface of the water, the bottom of the jar, and on the nail. Shake it off the nail and repeat until a generous amount of rust is formed. When enough rust has gathered, drain the excess water and spread the rust on a metal pan or sheet of aluminium foil in a warm or sunny place to dry. Once it is dry, scrape it off the pan or foil and crush it into a fine powder, and the rust is ready. Note that as electrolysis continues, the water is gradually lost and the concentration of aqueous sodium chloride increases. If pure water is not refilled at regular intervals, chlorine gas may be electrolysed eventually at the electrode connected to the adaptor's positive terminal because of saturation of chlorine ions. [edit] Electrolysis with Iron Anode 2 For a much more efficient manner, follow the instructions previously given for creating rust, but instead of using a nail or ruler, utilize fine steel wool. The reaction speed depends partially on exposed surface area, and this method works extremely fast to create large quantities of rust. Also consider using epsom salts instead of table salt to avoid producing chlorine gas. [edit] Hardware Store and Steel Wool Fe2O3 is also available at most hardware store and artist supply store as a pigment for concrete and oil paint. Something called "brick red" usually contains more than 60% of iron oxide which is pure enough for thermite. An easier, yet slower method, is to first soak a pad of fine steel wool in vinegar or another mild acid for a few days, then let it dry out over several more days. The action of the acid on the metal will expediate the oxidation of the iron into Iron III oxide. Alternatively, burning the steel wool will form Iron Oxide but is highly ineffective for making thermite using this formula. A more effective way is to mix bleach with fine steel wool. The reaction is quick. Adding vineger after mixing the steel wool and bleach together in a 2:1 ratio greatly increases the reaction speed and rust is produced instantly however the vineger and bleach (even in the presence of iron) produces toxic chlorine gas. This should only be done outside or in a fume hood. By burning the steel wool Fe3O4, or magnetite, is produced, while rusting the steel wool produces mostly hematite, Fe2O3, and some magnetite. [edit] Mixing the Iron Oxide and Aluminium Now, the iron oxide must be mixed with aluminium to create the final product, ferrous thermite. Use the balance to weigh the rust gathered. Use the basic formula below to determine the amount of aluminium needed: mass of iron oxide gathered / 3 = mass of aluminium needed. Note: The molecular weight of Fe2O3 (hematite) is 159.7, molecular weight of 2Al is 54.96. For a perfect molar ratio the mass of aluminium should be 0.3463 the mass of the rust. To reverse that, the rust should be approximately 2.888 the mass of the aluminium. Weigh the aluminium filings. Mix thoroughly. [edit] Ignition To prevent premature ignition, it is important to shield the thermite mixture from the sparks of the fuse or ignition device. Aluminum is a suitable shield as it is malleable and will melt instantly when the reaction begins so it will not stifle the spectacle. Because of the high temperature necessary to ignite the thermite, a magnesium strip is needed. Use a blowtorch, butane torch, or similar to light the magnesium strip, which will in turn light the thermite in a ladder-up reaction. Place the strip alongside the thermite. A potentially safer method if materials are available is to place ground potassium permanganate in a small crater in the thermite and pour glycerine on top. It is also possible to use certain types of sparkler fireworks and probably magnesium road flares. The magnesium fire starters used for camping will ignite thermite. A small (1cm3) crater should be dug in the mixture and filled with the filings scraped away from the magnesium block. An alternative method of igniting thermite is to use the head of an ordinary match. The simplist way to do this is to place the head of the match into the thermite, and then light the other end of the match. When it burns down to the bottom (the head), the chemical ignitor of the match will light and get hot enough, if only for a second, to ignite the thermite reaction. DO NOT USE THE STRIKER THAT COMES WITH THE FIRESTARTER. A proper ignition system must leave the experimenter enough time to reach a safe shelter. A fuse or a sparkler firework can be used to light the magnesium filings. Take caution in the use of container in which the thermite reaction is maintained. The molten mixture will burn through iron, tables, melt glass (or shatter it). The container is usually damaged beyond use. For up to 100 grams of mixture, two stacked clay flower pots will contain the molten iron slag but small sparkles will still fly around. Thermite reaction in large quantities should be held outside a laboratory in an open field. It will in all probability ruin any surface it is conducted on, including laboratory counters which are otherwise resistant to lower temperatures. Retrieved from "http://en.wikibooks.org/wiki/Chemical_synthesis:Thermite_synthesis"
I am presently occupied with experimenting in using thermite in cutting up and sinking ships. I can see a number of useful applications in my trade that have yet to be explored. We used thermite to weld rail together when I worked for ICGRR back 35 years ago and I always wondered about the underwater application of welding with it. I have been researching this for a while and will shoot some video next week when we use it to cut up a small wreck at the end of our Mobile property.
