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Reactives include chemicals that vigorously polymerize, decompose, condense, or explode when exposed to water, chemicals, air, or conditions of shock, pressure, or temperature. The reactions can result in flames or the release of toxic gas.
Following are examples of classes of reactives and the hazards associated with them.
Water reactives are chemicals that react violently and ignite or release toxic gas upon contact with water, water vapor, or air.
Examples include acetyl chloride, dimethyldichlorosilane, hydrazine, Grignard reagents, acetic anhydride, potassium or sodium cyanide, and hydrofluoric acid.
Dimethyldichlorosilane is flammable, poisonous, and corrosive. This chemical is extremely reactive and must be double-contained in a plastic outer container. For proper storage, the flammable characteristics must be given priority. Dimethyldichlorosilane should be stored in the flammable cabinet.
There are some chemicals that are sensitive to shock, heat, or friction. These chemicals are stable originally, but become unstable due to dehydration, decomposition, peroxide-formation, and mixing with other chemicals.
Picric acid or trinitrophenol is purchased as a solid or a liquid. The solid must have greater than 10% water. If picric acid is allowed to dry (to flow like sugar), it becomes explosive, sensitive to heat, shock, or friction. Turning the cap may cause an explosion. To prevent this problem, record the weight of the container when new and each time an amount is removed. If there is a great difference in the tare weight, water might have evaporated. Do not move old picric acid. Contact EH&S immediately for removal. For more information, refer to EH&S's website for detailed chemical safety information.
Peracetic acid is insensitive to shock but explodes violently at 100° C and has been reported to explode upon decomposition.
Ammonium nitrate is another chemical that will explode after decomposition.
Formic acid (98-100%) decomposes to carbon monoxide and water after prolonged periods of storage. The gas builds up significant pressure to cause explosion and potential injury. In 1984, formic acid manufacturers modified container caps to allow for the release of the pressure. If you have an older bottle with an ordinary cap, call EH&S for disposal.
Diethylpyrocarbonate (DEPC) has been shown to decompose causing the buildup of carbon dioxide. The pressure has been significant enough to release toxic liquid violently upon opening the container. DEPC new or opened should be opened in the chemical fume hood. Gloves, eye protection, and a lab coat should be worn and the lid must be unscrewed very slowly releasing any pressure buildup.
Hydrogen peroxide (30%) decomposes over time when exposed to sunlight releasing gaseous oxygen. The pressure buildup in a sealed container may become explosive over time. Therefore, you should vent hydrogen peroxide containers periodically by unscrewing the cap and releasing the gas.
Peroxide-forming chemicals are explosive if exposed to heat, shock, or friction. Please refer to Section 12.8, Peroxide Formers, for more information.
Sodium azide and other azides become shock-sensitive when in contact with metals. Sewer disposal of azides could lead to the formation of metal azides in metal pipes that explode upon contact.
Silver nitrate and ethanol have been reported to explode violently during the purification of silver nitrate. Call EH&S for the proper procedures when purifying silver nitrate.
Potassium cyanide and potassium ferricyanide can liberate cyanide gases when exposed to acids, heat, or ultraviolet radiation. Such an incident occurred in a photographic lab where potassium ferricyanide reacted with acid residue that had not been flushed from a sink trap. In addition, cyano-type processing, in which potassium ferricyanide and ferric ammonium citrate are mixed and spread onto a photo, has demonstrated the release of hydrogen cyanide after exposure to heat and ultraviolet radiation. Please make sure processes involving cyanide-containing compounds are performed in the chemical fume hood.
The combination of bleach (ClNaO) and lime (CaO) causes the release of chlorine gas, which is extremely irritating to the eyes and the upper respiratory system.
All of these reactive chemicals should be stored in double-containers and in their appropriate storage groups; see Section 9, Proper Chemical Storage. For example, hydrofluoric acid is corrosive and should be stored double-contained in Group 4: Organic and Mineral Acids in the organic corrosive storage cabinet. Double-containment can be either a plastic or glass outer container around the original container of the compound. A metal can or plastic bag is not appropriate if the chemical is corrosive. For water reactives that are not corrosive, but are flammable or toxic, a metal container may be used for secondary containment.
Most reactives must be labeled for collection by EH&S. See Chapter VI, Hazardous Waste Directory.
Complete an Accident-Illness Report Form as soon as possible and mail to EH&S at J3-200.
While wearing safety goggles, gloves, and a lab coat, you can absorb a small spill with a universal absorbent. For large spills (>200 ml), evacuate the lab and call EH&S for clean-up.