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Decomposition

Definition

• Decomposition is the breakdown or change of a material or substance (by heat, chemical reaction, or other processes) into other chemical compounds.
• Thermal decomposition is decomposition initiated by heating.
• Chemical decomposition is decomposition induced by the addition of one or more chemicals to a substance.

Additional Info

Just as a piece of food (which is really just a collection of many chemicals) can spoil or rot (see biodegradable), so can certain chemical substances or mixtures.

For example, when glucose (a form of sugar) is burned in air, it decomposes into carbon dioxide and water (this is also an example of a combustion reaction):



See this discussion of thermodynamics for more information about the energy involved in this and other reactions.

Living organisms exploit decomposition reactions in order to live. For example, the digestion of food is an exothermic process, which provides organisms with heat and chemical energy while converting the food to simpler substances that are then used as building blocks within the body or are discarded as waste.

As we live in a dynamic world, many of the everyday objects around us are thermodynamically unstable. Provided the conditions are right, they will decompose all by themselves or with a little help by Nature. Examples include bread, nitroglycerin, lawn clippings and more. Some of these processes generate enough heat on their own to undergo spontaneous combustion!

MSDS Relevance

Decomposition can have many effects, each of which is potentially hazardous:
1. New substances may be formed, some or all of which are explosive, flammable or toxic. Peroxide-forming materials are particularly dangerous.
2. Decomposition may result in the release of a large amount of heat, possibly resulting in a fire or explosion. The phrase "explosive decomposition" may appear on the MSDS.
3. Partial decomposition can introduce toxins or other unstable materials as well as degrade the physical properties of the material.
4. Polymerization of the material may occur, changing an easily handled liquid into an insoluble solid.

Further Reading The American Chemical Society's journal Chemical & Engineering News maintains a list of Safety Letters concerning materials involved in unexpected explosive decompositions. The UK's Health & Safety Directorate has a writeup on Explosions in Warehouses as part of a comprehensive guide to chemical warehouses. An animated gif version of everyone's favorite contact explosive, nitrogen triiodide, a graphic example of decomposition. Thermal Decomposition at Crescent Girls' School. A list of shock sensitive materials courtesy of DePauw U Environmental Health & Safety. See also: HMIS, incompatible chemicals, peroxide, polymerization. Additional definitions from Google and OneLook.

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Disclaimer: The information contained herein is believed to be true and accurate, however ILPI makes no guarantees concerning the veracity of any statement. Use of any information on this page is at the reader's own risk. ILPI strongly encourages the reader to consult the appropriate local, state and federal agencies concerning the matters discussed herein.