Abstract: A flexible compartmented package having a primary chamber serving as a mixing or reaction chamber, and one or more secondary chambers capable of being filled with a liquid, paste or similar substance to be mixed or reacted with a substance contained in the primary chamber. To enable any of the secondary chambers to be joined with the primary chamber in communication therewith, each of the secondary chambers is separated from the primary chamber by a sealing seam having a portion capable of being ruptured to destroy the seal by means of applying pressure to the secondary chamber which is intended to be joined with the primary chamber.