Chemical Incompatibility Hazards
If 2 or more materials, or chemicals, remain in contact indefinitely without reaction, they are compatible. If 2 or more materials in contact begin to react immediately, or even over a period of months or years, they are incompatible.
Chemical compatibility is not only of concern for the storage of the chemicals, but also for the disposal of unused or waste materials containing chemicals.
Accidents have occurred when mixing incompatible chemicals in disposal containers.
Bulging or corrosion of containers is a frequent early warning sign of hazardous incompatibility. Containers can become overheated, pressurised and ruptured. Other signs include temperature changes (e.g. temperature rise due to exothermic reaction), colour or viscosity change, formation of vapours, toxic gases (such as when acid mixed with cyanide produces hydrogen cyanide gas), foam, or sludges or crystals (for example organic peroxides). The formation of crystals on containers, especially around openings, should be treated with great caution. Some of these crystals are shock-sensitive, and can lead to fire or explosion.
The Table below provide examples of hazards caused by incompatible
materials.
Click here for examples of common chemicals and the materials with which they are incompatible.
Incompatibility, however, does not necessarily indicate a lasting hazard. For example, acids and bases (both corrosive) react to form salts and water. That solution itself may not be corrosive and might or might not cause hazards. However, there can be a considerable heat of reaction during the mixing of the acid and the base.
Some explosive combination of common materials:
Click here for storage requirements of incompatibly materials.