A package has a transport/storage state for storing powdery material which is to be mixed with a solvent to form a medical solution. The package includes a compartment which is at least partially defined by two opposing wall portions, and a connector. In the transport/storage state, the compartment contains the powdery material in the form of at least two distinct sets of powdery material of different compositions, where the opposing wall portions are brought into engagement with the powdery material so as to immobilize the sets of powdery material. When used for preparation of the medical solution, a fluid is selectively admitted into the package via the connector so as to expand the compartment and enable mixing of the sets of powdery material with the solvent in the compartment.