A device to mechanically decompose a barrier which separates two or more mutually miscible ingredients and to mix the said ingredients, preferably a mixer for amalgam in capsules. The device (1) comprises first members to fixedly hold the said ingredients and second members to impart to the said ingredients a sufficiently rapid motion to accomplish the said barrier decomposition and mixing. The said first members comprise a closable space (4) into which the said ingredients and said capsule (2) respectively are admissible and by which these or this respectively is or are respectively aligned with the said second members (14, 15). The said second members (14, 15) are arranged to be started only upon or after closing of the said closable space (4).
