This International Standard establishes criteria for the purity of photographic-grade potassium ferricyanide and describes the tests to be used to determine the purity.
BS ISO 3624:1994 history
1995BS ISO 3624:1995 Photography. Processing chemicals. Specifications for potassium ferricyanide
1995BS ISO 3624:1994 Photography - Processing chemicals - Specifications for potassium ferricyanide