Water Reactive Materials

Many chemicals found in the laboratory are unstable and incompatible with water. The hazards involved when water comes in contact with a water reactive material arises from one or more of the reactions shown in the following table.

Possible Reactions With Water

release of flammable gas

release of strong oxidizing gas

release of toxic gas

release of metal oxide fumes

formation of corrosive acids

The above reactions create a particularly hazardous situation for firefighters, since water is most commonly used for fighting fires. Water used to put out a fire involving water reactive materials will only serve to intensify the fire situation. In an effort to protect firefighters, the Department of Transportation (DOT) requires that a warning label ("Dangerous When Wet") be affixed to all water reactive materials. This label should also serve as a warning to all laboratory personnel to store and use these materials in areas where the use of water is restricted.

Water reactive chemicals should be stored in an isolated area within the lab, preferably in a water-tight cabinet well away from water use areas. This cabinet should be labeled "Water Reactive Materials - No Water". Suitable fire extinguishing materials (dry sand, class D extinguisher, etc.) should be provided in an immediately accessible area.

Examples of specific water reactive materials and classes of chemicals are provided in the following table.

Examples of Water Reactive Materials and Their Reaction Product

• Alkali metals (Na, K, Li) + water =

  detonation, heat, formation of hydroxide, hydrogen gas liberated
  

• Alkaline earths (Mg, Be, Ca, Ba) + water =

  detonation, hydrogen gas liberated
  

• Hydrides (LiH, LiAlH4) + water =

  hydrogen liberated, caustic solution left behind
  

• Carbides of Al, Ca, Mg + water =

  acetylene liberated
  

• Phosphides + water =

  phosphine gas liberated
  

• Nitrides + water =

  ammonia liberated, caustic solution left behind
  

• Metallic (inorganic, such as potassium) peroxides + water =

  oxygen gas and heat liberated
  

• Chlorides of group III metals, transition metals, non-metals (Al, Ti, S) + water =

  hydrogen chloride gas liberated

Copyright © 1996 by College of Science, Texas A&M University