Bleach-fix regeneration monitoring method

In a process for regenerating a spent bleach-fix photographic solution to restore its bleaching capability and thereby permit its reuse in photographic processing, the bleaching agent being a ferric complex of an aminopolycarboxylic acid, the spent bleach-fix solution comprising silver ion and ferrous ion as a result of its use in a bleach-fix step of photographic processing which process of regeneration comprises in series a first silver replacement step in which silver ion in the spent bleach-fix solution is chemically replaced by reduction using elemental iron, and an oxidation step in which ferrous ion in the spent bleach-fix solution is oxidized to ferric ion;

• the improvement comprising monitoring said regeneration process by electrochemically comparing the half-cell potential of the ferric-ferrous couple in a sample of the bleach-fix solution drawn from either said first silver replacement step or said oxidation step, with the half-cell potential of the ferric-ferrous ion couple in a reference solution drawn from a region of said regeneration process in which the bleach-fix solution is substantially insensitive to exhaustion of said elemental iron and insufficient oxidation, whereby either exhaustion of said elemental iron is detected when said sample bleach-fix solution is drawn from said first silver replacement step or insufficient oxidation is detected when said sample bleach-fix solution is drawn from said oxidation step.