Overview
ISO 4742:1984 specifies a gravimetric method for the determination of nickel content in copper alloys. The standard covers principle, reagents, apparatus, detailed procedure, expression of results and test report requirements. It is applicable to nickel contents between 2% and 50% (m/m). The procedure requires dissolution of the sample, removal of interfering elements (tin, silicon), separation of copper by electrolysis, and precipitation of nickel as the dimethylglyoxime complex for gravimetric measurement. Normal precautions for perchloric acid use are emphasized.
Key topics and requirements
- Scope: Applicable for Ni content from 2 to 50% (m/m).
- Principle: Dissolve sample in nitric acid, remove tin/silicon if present, electrolyze to remove copper (per ISO 1554), precipitate nickel with sodium dimethylglyoximate in presence of citric acid, filter, dry and weigh precipitate.
- Reagents (examples):
- Nitric acid, perchloric acid, hydrobromic acid, ammonia solution
- Sulfamic acid, citric acid solution
- Sodium dimethylglyoximate solution (precipitant)
- Apparatus: Standard laboratory glassware, electrolytic beakers (300–400 ml), electrolysis equipment with platinum electrodes (as specified in ISO 1554), fritted glass filter crucible (16–40 µm).
- Test portion guidance:
- Ni 2–4.25%: ~2 g sample (≈40–85 mg Ni)
- Ni 4–8.5%: ~1 g sample (≈40–85 mg Ni)
- Ni 8–50%: 0.25–1 g sample (≈80–125 mg Ni)
- Key steps: dissolution, oxide expulsion (boiling), electrolysis to remove copper, acid treatment and precipitation with sodium dimethylglyoximate, filtration on dried fritted crucible, drying 1 h at 150 °C, weighing.
- Expression of results: Nickel content expressed as percentage by mass. The standard gives the calculation using the mass of the dimethylglyoxime precipitate and mass of test portion (formula includes a constant factor present in the standard).
- Safety note: Observe precautions when using perchloric acid and other hazardous reagents; hydrobromic acid used to volatilize tin.
Applications and users
- Quality control and composition verification in copper alloy manufacturing (brass, bronze, cupronickel)
- Metallurgical and chemical analysis laboratories performing elemental assay of alloys
- Material certification, incoming inspection, and compliance testing against material specifications
- Failure analysis and research where accurate nickel quantification is required
Related standards
- ISO 1554 - Wrought and cast copper alloys: electrolytic determination of copper (electrolysis parameters cited by ISO 4742)
Keywords: ISO 4742:1984, copper alloys, nickel determination, gravimetric method, sodium dimethylglyoximate, electrolysis, perchloric acid safety, ISO 1554, laboratory analysis.