Apparatus for the preparation and dispensing of liquids which are used in developing machines for photosensitive material has a vessel with an upright partition over which a freshly formed mixture containing at least one liquid substance can overflow from a mixing chamber into a storage chamber. The latter has a bottom wall disposed at a level below the bottom wall of the mixing chamber and provided with an outlet which discharges mixture into a collecting container. A pump is provided to circulate the liquid substance along an endless path extending in part through the mixing chamber, and the partition has an opening slightly above or at the level of the bottom wall of the mixing chamber to permit direct flow of mixture between the two chambers when the mixture in the storage chamber reaches a certain level. The flow of mixture through the opening is controlled by a valve including a float.