Established are criteria of purity of chemicals suitable for processing photographic materials. A 'photographic grade' chemical is one which meets purity requirements as described. Specified are the limiting concentrations and test methods for certain impurities that may be present.
CHEMICAL ANALYSIS CHEMICAL ANALYSIS AND TESTING CHEMICAL COMPOUNDS CHEMICALS CONNECTIONS IMPURITIES MATERIALS SPECIFICATION MATERIALS SPECIFICATIONS PHOTOGRAPHIC CHEMICALS PHOTOGRAPHIC MATERIALS PHOTOGRAPHY SODIUM THIOSULPHATE SODIUM THIOSULPHATES TESTING TESTS CHEMICAL ANALYSIS AND TESTIN