Abstract: An automatic system is disclosed for obtaining and maintaining a controlled volume of solution above a body of soluble solid in a container by the automatic addition of solvent. The apparatus includes a sensor for sensing the distance between the upper surface of the soluble solid in the container and a point on a float which floats in the solution produced by the action of the solvent on the soluble solid. Solvent is added when this distance reaches a predetermined value and solvent addition ceases when the distance increases to a second predetermined value. Most advantageously, the container will be the same one used to ship the soluble solid.