ISO 423:1994 Preview
Photography -- Processing chemicals -- Specifications for hydroquinone
This standard was last reviewed and confirmed* in 2016.
*Therefore this version remains current
Establishes criteria for the purity and describes the test methods for identity tests, residue after ignition, heavy metals content, iron content, appearance of solution. Annex A describes preparation of the standard ammonium cerium(IV) hexanitrate solution.