Overview
ISO 7105:1985 - Liquefied anhydrous ammonia for industrial use - Determination of water content - Karl Fischer method specifies a laboratory procedure for measuring the water content of liquefied anhydrous ammonia using the Karl Fischer direct electrometric titration. The method applies to samples with water contents ≥ 50 mg/kg. For high water levels (> 1 000 mg/kg), the standard recommends diluting the evaporation residue with anhydrous methanol (per ISO 4276) and titrating an aliquot.
Key topics and requirements
- Scope and applicability: Designed for industrial-grade liquefied anhydrous ammonia; applicable from 50 mg/kg upward.
- Principle: Evaporate a weighed test portion in the presence of 1,2-ethanediol (ethyleneglycol) to leave a water/ethanediol residue, then determine water by the Karl Fischer direct electrometric method.
- Reagents and materials: Includes freezing mixture (CO2/methanol), sulfuric acid solution, 1,2-ethanediol (very hygroscopic), methanol/acetic acid mixture, and Karl Fischer reagent of analytical grade.
- Apparatus & sampling: Uses a specified glass collection/test tube assembly, Dewar vessel, and conical flasks to collect liquefied ammonia (follow sampling procedure in ISO 7103). Stopcocks must be PTFE or silicone-greased.
- Procedure highlights:
- Collect and weigh a laboratory sample in a cooled test tube.
- Evaporate ammonia slowly to obtain residue; rinse residue into the Karl Fischer titration vessel using methanol/acetic acid mixture.
- Run a simultaneous blank and perform direct electrometric titration per ISO 760.
- Results & reporting: Water content expressed as percentage by mass of H2O. Test report must include sample ID, method reference, titration volumes (including blank), test portion mass, calculated result and any unusual observations.
- Safety: Emphasizes strong hazards of liquefied anhydrous ammonia (toxic, corrosive, -33.3 °C boiling point). Operations must be performed in a well‑ventilated fume cupboard with appropriate PPE (rubber gloves, apron, full-face/head protection, protective gas‑mask).
Practical applications and users
- Quality control and acceptance testing for industrial ammonia suppliers and users.
- Analytical and calibration laboratories performing routine water determination in bulk ammonia.
- Process engineers and storage/transport specialists monitoring product quality and safety.
- Regulatory and procurement teams requiring standardized, traceable water-content data for compliance, safety, and product specifications.
Related standards
- ISO 760 - Determination of water - Karl Fischer method (general method)
- ISO 4276 - Anhydrous ammonia for industrial use - Evaluation of residue on evaporation (gravimetric method)
- ISO 7103 - Liquefied anhydrous ammonia - Sampling
- ISO 3165 - Safety in sampling
Keywords: ISO 7105:1985, liquefied anhydrous ammonia, water content determination, Karl Fischer method, ethanolediol, methanol dilution, ISO 760, ISO 4276, industrial ammonia testing, water in ammonia.
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