In practice the term refers to particles or pieces of aluminium with a surface coating of the amalgam.
The reaction and the waste from it contains mercury, so special safety precautions and disposal methods are needed.
As an environmentally friendlier alternative, hydrides or other reducing agents can often be used to accomplish the same synthetic result.
However, if any elemental aluminium is exposed (even by a recent scratch), the mercury may combine with it to form the amalgam.
The electrons from the aluminium reduce mercuric Hg2+ ion[clarification needed] to metallic mercury.