Abstract: A batch of dialysate solution is made from a mixture of bicarbonate formulation and a liquid acid formulation. The liquid acid formulation is introduced into a dialysate tank and then removed from the tank and stored elsewhere, such as in an ultrafiltration tank, where it is diluted with a few litres of water. The dialysate tank is then filled with water and the bicarbonate formulation is added to the dialysate tank. The bicarbonate formulation is mixed and dissolved by circulation in a closed loop, with the liquid acid formulation kept separate. When the bicarbonate solution has been prepared, the liquid acid solution and the bicarbonate solution are mixed together and stored in the dialysate preparation tank. An additional quantity of dilution water is introduced into the dialysate system to bring the final conductivity down to the desired range. The excess dialysate solution can be used for several purposes, such as an endotoxin flush of the blood tubing set or a dialyzer clearance test.