ISO 10084:1992

Overview

ISO 10084:1992 specifies a gravimetric method for the determination of mineral‑acid‑soluble sulfate content in solid fertilizers. The method is designed for fertilizers with sulfate contents, expressed as SO3, in the range 3% to 50% (dm). It defines the analytical principle, required reagents, apparatus, sample preparation references and calculation and reporting rules for routine laboratory determination.

Key topics and technical requirements

• Analytical principle: dissolve acid‑soluble sulfates in hydrochloric acid, precipitate sulfate as barium sulfate (BaSO4) using barium chloride, filter, wash, dry, ignite and weigh the precipitate (gravimetric determination).
• Reagents: analytical‑grade reagents including hydrochloric acid, barium chloride dihydrate (c = 122 g/l), and silver nitrate solution for chloride testing.
• Apparatus: common laboratory equipment supplemented by:
  • electric hot‑plate,
  • filter crucibles with porcelain disc (porosity grade P10),
  • ovens capable of 120 °C and 800 °C,
  • desiccator.
• Sample preparation: prepare laboratory sample according to ISO 8358 and take an adequate test portion so the SO3 in the test portion is 200–600 mg (select test portion mass per clause/table guidance).
• Procedure highlights: boiling in HCl, dilution and filtration, controlled precipitation at ~60 °C with BaCl2, thorough washing to remove chlorides (verified with AgNO3), drying at 120 °C, ignition at 800 °C, and weighing to 0.1 mg.
• Calculation: mineral‑acid‑soluble sulfate as SO3 is calculated using: Ws = 85.75 × m1 / m0 where m1 = mass of dried/ignited BaSO4 precipitate (g) and m0 = mass of test portion (g). Results are rounded to 0.01% (dm).
• Precision: method precision established by inter‑laboratory studies (ISO 5725). Repeatability and reproducibility limits are defined by formulae in the standard:
  • r = 0.042% + 0.0091 × Es (repeatability)
  • R = 0.098% + 0.0284 × Ws (reproducibility)

Applications and users

• Quality control and production testing in fertilizer manufacturing.
• Regulatory compliance testing where official sulfate content certification is required.
• Analytical and contract laboratories performing routine fertilizer chemical analysis.
• Agronomists and R&D groups verifying sulfate supply in soil conditioners and fertilizer blends.
• Standardization bodies and proficiency testing organizers using validated gravimetric procedures.

Related standards

• ISO 8358 - Preparation of samples for chemical and physical analysis of solid fertilizers (sample splitting and lab sample).
• ISO 5725 - Precision of test methods (used to establish repeatability and reproducibility).

Keywords: ISO 10084:1992, solid fertilizers, mineral‑acid‑soluble sulfate, gravimetric method, sulfate determination, BaSO4 precipitation, fertilizer analysis, ISO 8358, ISO 5725.