Abstract: A processing bath is accommodated in a container having a pipe which communicates with the interior of the container at two different locations of the latter. The bath is circulated through this pipe and a pump for circulation of the bath is provided in the pipe. Several tubes extend into the bath and each tube has an outlet opening in the region of the inlet end of the circulation pipe. The outlet openings of the tubes are all located at different levels below the surface of the bath. The tubes are respectively connected with supply pumps which, in turn, are connected with respective sources of concentrates and a diluent required to maintain the strength of the bath within predetermined limits. A sensor senses the amount of material processed in the bath and causes the supply pumps to pump the concentrates and diluent into the bath in dependence upon the amount of material processed.

Abstract: A method of mixing at least one chemical concentrate with a thinning fluid to form a predetermined amount of a mixture or solution having a predetermined composition, particularly for use in photographic processing operations. Predetermined amounts of the concentrates are placed into respective holding units. The contents of the holding units are emptied into a mixing conduit which leads to a supply tank while at the same time thinning fluid is passed through the mixing conduit. The flow of thinning fluid through the mixing conduit is terminated when the amount of thinning fluid which has been passed through the mixing conduit reaches the amount corresponding to the predetermined amounts of the initial concentrates and to the predetermined amount of final solution or mixture desired.