Amagnesium torch is a bright light source made frommagnesium, which can burn underwater and in all weather conditions. They are used for emergency illumination for railroad applications. They were also used in the 1950s up to the early 1970s as a light source forscuba diving, and were featured occasionally in television shows. A relay of magnesium torches was used to transfer the Olympic flame from Greece to the site of the Olympic games several times since the first occasion at the 1936 Berlin Games.[1]
Magnesium is highly flammable, burning at a temperature of approximately 3,100 °C (3,370 K; 5,610 °F),[2] and theautoignition temperature of magnesium ribbon is approximately 473 °C (746 K; 883 °F).[3] It produces intense, bright, white light when it burns. Once ignited, magnesium fires are difficult to extinguish, because combustion continues innitrogen (formingmagnesium nitride),carbon dioxide (formingmagnesium oxide andcarbon), and water (forming magnesium oxide and hydrogen).
Details may vary depending on the application. For railway emergency lighting and signalling purposes, the torch may consist of a rolled cardboard structural tube with plastic end covers, one of which may be the ignition device. The fuel is inside and exposed by removing the top end cap.[4] This type of construction may be unsuitable for underwater use.
Underwater use produces large volumes of hydrogen gas, which if trapped in a confined space with exhaled breathing gas, which typically contains more than 17% oxygen by volume, can form a flammable or explosive gas mixture. The range of explosive mixtures of hydrogen and air or oxygen is unusually wide, but varies with temperature, pressure and other factors.[6]A magnesium torch does not necessarily give warning of an atmosphere that cannot support life or consciousness, as it continues to burn underwater, or in an oxygen free atmosphere if sufficient nitrogen or carbon dioxide are present.
An underwater torch is available in the Education Edition of theMinecraft sandbox video game, created by combining a torch with magnesium on a crafting table.[7]
Featured occasionally in theSea Hunt television show.[8]
Magnesium torches were used in the documentary seriesThe Undersea World of Jacques Cousteau. "The Secrets of the Sunken Caves" (episode 17, released in 1971) features the divers using these torches to explore a deep underwater cave.[9]
^Dreizin, Edward L.; Berman, Charles H. & Vicenzi, Edward P. (2000). "Condensed-phase modifications in magnesium particle combustion in air".Scripta Materialia.122 (1–2):30–42.CiteSeerX10.1.1.488.2456.doi:10.1016/S0010-2180(00)00101-2.
^"Magnesium (Powder)".International Programme on Chemical Safety (IPCS). IPCS INCHEM. April 2000. Retrieved21 December 2011.
^Hopkins, George Milton (1911).Experimental Science : Elementary, Practical and Experimental Physics. Vol. 2 (27th ed.). New York: Munn and Company Inc. p. 291.
