Dialysis is a temporary method of treating a person with kidney failure. The blood from the patient is drained and heparin is added to it as an anticoagulant. The dialysing unit has a cellophane membrane, and a dialysing fluid with the same composition as plasma except the nitrogenous wastes. Therefore when the patient's blood is passed the nitrogenous wastes diffuse out. Once the blood is filtered it is pumped back into the patient.