Abstract: A method and apparatus are provided in which silver ions are removed from a photographic fixer solution in a simple and efficient manner. The electrical conductivity of the solution is measured, which is effectively that of the fixer (thiosulphate). The electrical potential of the solution is measured between two electrodes immersed therein. A predetermined algorithm is applied to the two values to determine the silver ion concentration. If this is above a predetermined level, a silver recovery unit is activated. The measurements allow this unit to operate more efficiently than hithertobefore.

Abstract: A method and apparatus is provided for quickly shimming a tubular supermat to function in several different environments which create unique impurity gradients to interfere with uniformity of the electromagnetic field from the supermagnet. Non-magnetic tubes are secured to the supermagnet casing for receiving non-magnetic shim supporting rails. The shim supporting rails carry magnetic material masses, usually steel, for precise location on the periphery of the supermagnet casing. Holes may be cut into the supermagnet shroud for introducing and withdrawing the shim support rails. Arcuate aesthetic covers for the shroud holes are provided to restore the aesthetic appearance of the shroud.