Overview
ISO 10348:1993 - "Photography - Processing wastes - Determination of silver content" specifies laboratory methods for measuring silver in photographic processing effluents. The standard describes three analytical procedures (one flame atomic absorption spectroscopy (AAS) method and two potentiometric iodide titration (PT) methods) plus two sample‑treatment routes (cyanogen iodide stabilization and two digestion procedures). It covers sampling, preservation, reagent preparation, apparatus, procedures, calculations and safety precautions specific to photographic wastes.
Key topics and technical requirements
- Analytical methods
- Flame AAS: measures silver atom absorption; can directly analyze samples preserved with cyanogen iodide (CNI) after appropriate dilution and calibration.
- Potentiometric iodide titration (PT): two PT procedures using an iodide titrant and a silver/iodide-sensitive electrode; titration requires digestion to solubilize silver and remove interferences.
- Sample treatment
- Cyanogen iodide (CNI) preservation is the preferred stabilizer for silver in photographic effluents (prevents acid‑induced precipitation that occurs with nitric acid).
- Digestion A: for low‑salt, low‑solids effluents - includes concentration and a boiling step.
- Digestion B: for high‑solids or heavily contaminated samples - more vigorous digestion to recover particulate silver.
- Performance and limits
- Practical lower limits cited: AAS ≈ 0.1 mg/L; PT (Digestion A) ≈ 0.2 mg/L under specified conditions. Inter‑laboratory 95% confidence limits and precision data for Digestion A and AAS are provided in the standard.
- Safety and handling
- Detailed hazard warnings (CNI is hazardous; risk of hydrogen cyanide evolution during digestion). Mandatory safety practices include fume hood use, protective equipment, and the strict prohibition of pipetting by mouth (use bulb/plunger).
- Supporting information
- Annex A gives reagent preparation (CNI, silver standards, iodide/silver titrants) and the standard lists normative references for glassware, sampling and reagent quality.
Applications and users
- Who uses it
- Photographic laboratories, environmental compliance units, industrial wastewater analysts, contract testing labs and regulatory agencies concerned with silver discharge from photographic processing.
- Practical applications
- Routine monitoring of photographic effluents for regulatory compliance.
- In‑house or outsourced analysis to quantify dissolved and particulate silver.
- Method selection guidance (AAS for rapid analysis of CNI‑preserved samples; PT for samples needing digestion).
Related standards
Relevant referenced standards include sampling and laboratory‑ware and reagent quality norms such as ISO 5667 (water sampling), ISO 835 (pipettes), ISO 1042 (volumetric flasks), ISO 3696 (water for analysis) and ISO 6353 (reagents).
Keywords: ISO 10348:1993, silver determination, photographic processing wastes, cyanogen iodide, AAS, potentiometric iodide titration, sample preservation, digestion methods, photographic effluents, wastewater analysis.