Overview
ISO 422:1994 - Photography - Processing chemicals - Specifications for p‑methylaminophenol sulfate - defines purity criteria and test methods for photographic‑grade p‑methylaminophenol sulfate (HOC6H4NHCH3·½H2SO4). This second edition (1994) cancels the 1976 first edition and specifies chemical and physical requirements, sampling, and analytical procedures to ensure material suitability for photographic processing solutions.
Key topics and requirements
The standard sets mandatory limits and describes analytical methods. Principal technical topics include:
- Assay (purity)
- Cerate titration: 99.0 % (m/m) min. and 102.0 % (m/m) max.
- Alkali titration: 97.5 % (m/m) min.
- Identity tests
- Melting point of the nitroso derivative: 130 °C to 135 °C; mixed melting point must not be less than the sample or standard.
- Optional infrared (IR) spectrum to match a reference absorption curve.
- Impurity and physical limits (Table summary)
- Residue after ignition: ≤ 0.10 % (m/m)
- Heavy metals (as Pb): ≤ 0.002 % (m/m) (ISO 10349‑5 methods)
- Iron (Fe): ≤ 0.005 % (m/m)
- Volatile matter: ≤ 0.3 % (m/m) (ISO 10349‑8 methods)
- p‑Aminophenol: ≤ 2.5 % (m/m) (UV spectrophotometry at 312 nm)
- Solubility in diethyl ether: ≤ 0.2 % (m/m)
- Appearance of solution: Clear, not more than slightly yellow
- Analytical methods and apparatus
- Titrations (cerate, alkali), pH potentiometry, IR spectroscopy, UV spectrophotometry, residue‑after‑ignition, and heavy‑metal/iron determinations.
- Tests are performed on samples “as received” to reflect supplied material.
- Handling and storage
- Store in a closed container at room temperature; follow laboratory safety (protective gloves, goggles). ISO 10349 series referenced for general test procedures and hazard codes.
Practical applications
- Quality control and acceptance testing for photographic chemical manufacturers and suppliers.
- Procurement specifications for photographic‑processing operations and R&D labs evaluating developer components.
- Regulatory or compliance checks where defined purity prevents photographic defects (fogging, staining) or downstream process variability.
Who should use this standard
- Chemical analysts and QC laboratories in photographic and imaging supply chains.
- Manufacturers of photographic processing chemicals and formulators.
- Technical procurement specialists and standards compliance officers in imaging industries.
Related standards
- ISO 10349 series (Parts 1, 4, 5, 8) - general test methods for photographic‑grade chemicals.
- ISO 565 - test sieves referenced for IR sample preparation.
Keywords: ISO 422:1994, p‑methylaminophenol sulfate, photography processing chemicals, assay, cerate titration, alkali titration, residue after ignition, heavy metals limit, infrared spectrum, p‑aminophenol limit.