The invention concerns a multiple compartment flexible bag assembly including a first predetermined volume of an aqueous sodium bicarbonate component solution contained in at least one of the multiple compartments and a second predetermined volume of an aqueous acid component solution contained in at least another of the multiple compartments, the component solutions being intended to be mixed together to obtain a peritoneal dialysis, hemodialysis or replacement fluid, characterized in that the aqueous acid component solution comprises an amount of dissolved carbon dioxide. The partial pressure value of carbon dioxide exhibited the aqueous acid component solution is preferably matched with the partial pressure value of carbon dioxide determined for the aqueous sodium bicarbonate component solution.
