ISO 3139:1976

Overview - ISO 3139:1976 (Aqueous hydrofluoric acid - Sampling & methods of test)

ISO 3139:1976 specifies standardized procedures for sampling and chemical testing of aqueous hydrofluoric acid (HF) for industrial use. The standard covers safe sample preparation and a set of titrimetric methods to determine: total acidity, hexafluorosilicic acid (H2SiF6) content, non‑volatile acids content, and a calculation method to derive the hydrogen fluoride (HF) content from those determinations. The edition consolidates an earlier addendum and applies to industrial HF solutions in the typical commercial range (about 40–85% mass).

Key topics and technical requirements

• Scope and application: Laboratory titrimetric methods for industrial HF solutions; method applicability ranges are specified (for example, H2SiF6 typically 0.2–10% mass; non‑volatile acids 0.025–5% mass).
• Sampling & sample preparation: Use polyolefin sample bottles (150 ml capacity), dilution and cooling of hazardous samples, and use of ice/water mixtures to prepare test samples. Samples must be handled under a fume hood.
• Titrimetric procedures:
  • Determination of total acidity and hexafluorosilicic acid: a two‑stage titration - a cold titration (in presence of KNO3 and phenolphthalein) followed by a hot titration; uses standardized NaOH titrants (1 N and 0.1 N are referenced).
  • Determination of non‑volatile acids: evaporation to remove volatile acids, then titration at 100 °C with 0.1 N NaOH using phenolphthalein.
• Calculation of HF content: HF mass percent is calculated from measured values using the formula:
  • HF = a − 0.833·b − 0.408·c
    • where a = total acidity (% mass HF), b = H2SiF6 (% mass), c = non‑volatile acids (% mass as H2SO4).
• Reagents and apparatus: Specifies analytical‑grade reagents (distilled water, KNO3, NaOH titrants, phenolphthalein), common lab glassware/containers (polyolefin, PTFE), and platinum capsules for evaporation steps.
• Safety: Emphasizes HF hazards - extreme corrosivity, glass attack, severe skin/eye burns - and mandates PPE and fume hood use.

Practical applications and users

ISO 3139 is used by:

• Chemical producers and refineries that manufacture or distribute industrial HF
• Quality control and analytical laboratories performing routine compositional analysis
• Materials suppliers and downstream users (fluorination, etching, metal treatment industries) who require verified HF composition
• Regulatory and safety auditors assessing compliance with handling and testing procedures

Benefits include consistent test results, safer handling practices for hazardous samples, and a reliable basis for product specification and quality control.

Related standards

Relevant ISO documents (annex) include:

• ISO 3137 (anhydrous HF sampling)
• ISO 3138 (non‑volatile acids titration)
• ISO 3699 / 3700 (water determination: Karl Fischer, conductimetric)
• ISO 3701 (H2SiF6 photometric method)
• ISO 3702 (SO2 determination)

Keywords: ISO 3139, aqueous hydrofluoric acid, sampling, methods of test, titrimetric methods, total acidity, hexafluorosilicic acid, non‑volatile acids, hydrogen fluoride content, HF analysis.