ISO 10248:1996

Overview - ISO 10248:1996 (Fluid fertilizers - De-aeration by film disentrainment)

ISO 10248:1996 specifies a laboratory procedure for the de‑aeration of suspension samples of fluid fertilizers prior to physical testing. The method uses a rotating‑film (film disentrainment) technique under reduced pressure to remove entrained air while minimising viscosity effects and additional air incorporation. It is intended for routine sample preparation where free ammonia is only present as a trace and where viscosity and stability permit the technique.

Key topics and technical requirements

• Scope and limitations
  • Applies to de‑aeration of suspension samples intended for physical tests.
  • Not suitable when the sample contains more than a trace of free ammonia, shows permanent decomposition, or is too viscous.
• Principle
  • Film disentrainment: form a thin film of suspension on a rotating flask to shorten bubble travel distances and promote release of entrained air under reduced pressure.
  • Slow liquid movement reduces viscosity effects and prevents re‑entrainment of air.
• Apparatus
  • Laboratory equipment with specific requirements:
    • Rotary evaporator with minimum 1 L flask capacity and evacuation capability to around 2 × 10^4 Pa (as specified for the apparatus).
    • Water bath able to maintain 25 °C ± 2 °C.
• Procedure (summary)
  • Transfer ~500 g of sample into a clean, dry 1 L flask and weigh to 0.1 g accuracy.
  • Mount flask on the rotary evaporator; set to minimal rotation to produce a thin film.
  • Immerse flask body in 25 °C bath; avoid using the condenser refrigeration and avoid higher bath temperatures to prevent component decomposition (e.g., urea).
  • Reduce system pressure to about 4 × 10^4 Pa and operate for approximately 15 minutes.
  • Return the system slowly to atmospheric pressure, dry the flask exterior and re‑weigh (mass loss should not exceed 0.1%).
  • Carefully sample for subsequent physical tests; store sealed for up to 3 days if testing is delayed.

Applications and users

• Practical for:
  • Quality control laboratories in fertilizer manufacturing
  • Research and development teams evaluating physical properties (density, rheology, homogeneity) of liquid fertilizers
  • Test laboratories preparing suspension samples for standardized physical testing
• Benefits:
  • Produces reproducible, low‑air samples for accurate physical measurements
  • Minimises thermal or mechanical alteration of sensitive fertilizer components when used as specified

Related standards and context

• Published by ISO (ISO/TC 134 - Fertilizers), ISO 10248:1996 complements other ISO methods for fertilizer analysis and physical testing. For complete laboratory programs, consult additional ISO fertilizer standards and national test methods from ISO/TC 134.

Keywords: ISO 10248:1996, fluid fertilizers, de‑aeration, film disentrainment, suspension samples, rotary evaporator, sample preparation, physical testing.