Overview - ISO 3220:1975 (Copper and copper alloys - Determination of arsenic - Photometric method)
ISO 3220:1975 specifies a photometric (spectrophotometric) method for the determination of arsenic in copper and copper alloys. It covers the full analytical workflow: principle, reagents, apparatus, sampling, detailed procedure, expression of results and test reporting. The method is applicable when arsenic is present either as an alloying element or as an impurity in copper and in all types of copper alloys referenced in ISO publications.
Key topics and technical requirements
- Analytical principle: Extraction of arsenic into benzene from an acidified solution, re-extraction to aqueous phase, and colorimetric determination as molybdenum blue (spectrophotometric measurement).
- Reagents listed: benzene; hydrochloric, hydrobromic, perchloric and sulphuric acids; hydrogen peroxide; potassium permanganate; ammonium heptamolybdate (molybdate reagent); ascorbic acid; arsenic stock and standard solutions. Reagents must be of analytical grade with distilled or deionized water.
- Apparatus: standard laboratory glassware and a photometer. Measurement wavelengths are 840 nm (primary, max absorption) and 578 nm (alternative, mercury line) using 1 cm or 2 cm cells depending on arsenic amount.
- Sample/test portion guidance: specified sample masses and aliquot sizes for expected arsenic ranges (e.g., up to 0.02% uses 2 g portions; 0.02–0.8% uses 0.5 g portions). Procedure includes controlled evaporation, oxidation (permanganate), molybdate reaction and development with ascorbic acid.
- Interferences: phosphorus and silicon at milligram amounts are reported not to interfere.
- Calibration and expression: prepare calibration graph with arsenic standards; calculate arsenic content as percentage by mass. Blanks must be determined and results corrected.
- Reporting: include method reference, results and expression, notable characteristics and any non‑standard operations.
Applications and who uses ISO 3220
- Metallurgical and analytical laboratories performing chemical analysis of copper and copper alloys for quality control, specification compliance, and material certification.
- Copper producers, recyclers and alloy manufacturers monitoring arsenic as an impurity or controlled alloying element.
- Regulatory and standards bodies and testing services that require reproducible, standardized arsenic determination methods.
- Useful where a photometric/spectrophotometric approach is preferred over instrumental techniques (e.g., atomic absorption), or where harmonized ISO methodology is required.
Related standards
- Prepared by ISO/TC 26 (Copper and copper alloys). ISO 3220 is intended to be used alongside other ISO recommendations and standards for copper alloys (refer to the relevant ISO publications for sampling and alloy specifications).