Overview
ISO 10702:1993 specifies a titrimetric method after distillation for the determination of nitrogen in steel and iron. The standard defines the chemical principle, apparatus, reagents and detailed procedure for quantitative analysis of nitrogen in metallic samples. It is applicable to nitrogen contents from 0.002 % (m/m) to 0.5 % (m/m) and explicitly excludes samples containing silicon nitride. Annex A gives example steam-distillation assemblies; Annexes B and C summarize interlaboratory precision data.
Key topics and technical requirements
- Analysis principle: dissolve test portion in hydrochloric acid, oxidize with hydrogen peroxide, fume the acid‑insoluble residue in sulfuric acid with potassium sulfate and copper(II) sulfate, make the solution alkaline with sodium hydroxide, distill ammonia into orthoboric acid solution, then titrate the collected ammonium with amidosulfuric acid.
- Measurement range: 0.002 % to 0.5 % nitrogen (m/m).
- Exclusion: not applicable to samples containing silicon nitride or other fine nitrides unless special filtration is used.
- Reagents & apparatus: requires analytical‑grade reagents (HCl, H2O2, H2SO4, NaOH, orthoboric acid, amidosulfuric acid), grade A volumetric glassware, burette, and steam‑distillation apparatus (examples in Annex A).
- Quality control: duplicate blank tests are required with each batch to monitor contamination; recommended blank reproducibility limits are given. The method’s precision (repeatability and reproducibility) was established by international trials and treated per ISO 5725.
- Safety & contamination control: perform operations in a well‑ventilated area and use cleaned, reserved glassware; hydrogen peroxide and strong acids require careful handling.
Practical applications
- Routine metallurgical quality control for steel mills, foundries and iron producers to monitor nitrogen content.
- Laboratory certification and compositional analysis for alloy specification compliance.
- Research and failure analysis where accurate determination of nitrogen influences properties (e.g., hardness, embrittlement, nitriding process control).
- Applicable for low‑level nitrogen determinations in unalloyed and alloy steels and pig iron within the stated concentration range.
Who should use this standard
- Metallurgical and analytical laboratories performing elemental analysis of steel and iron.
- Quality assurance engineers and materials scientists involved in production control.
- Accreditation bodies and auditors assessing laboratory methods against ISO requirements.
Related standards
- ISO 3696 - Water for analytical laboratory use
- ISO 377‑2 - Sampling for chemical composition of wrought steels
- ISO 385‑1, ISO 648, ISO 1042 - Laboratory glassware standards
- ISO 5725 - Precision of measurement methods (repeatability/reproducibility)
Keywords: ISO 10702:1993, nitrogen determination, steel and iron, titrimetric method, distillation, ammonium titration, amidosulfuric acid, orthoboric acid, precision, repeatability, reproducibility.