Abstract: A container in the form of a soft plastic bag divided into at least two and possibly three non-communicating chambers. The first two chambers may contain predetermined quantities of physiological salt washing solution for the extracorporeal circuit on the blood. side of a dialysis apparatus before employment of the apparatus in dialysis. Physiological salt solution in the first chamber may be used for washing the circuit by recirculation, if necessary, after an initial quantity of physiological salt solution has passed through the circuit and has been removed or discharged into the third chamber. Physiological salt solution in the second chamber may be utilized to complete the washing of the circuit and, if necessary, for replacement of water in the patient's blood to the patient's body at the end of the dialysis.