The automation of Clay Fraction analysis (ISO 11277)

In Europe, the determination of the clay fraction or “LUTUM” (Method of Robinson-Köhn, ISO11277) is used to characterize soil for construction works or to determine the capacity of soil to transport pollution.

The analysis to determine the clay fraction is carried-out in 5 steps:

  • Weighing the sample
  • Removal of Organic Matter
  • Removal of Carbonates
  • Transferring a portion of the sample into a 1000 ml measuring cylinder
  • Determination of the clay fraction

The last step in this process, the determination of the clay fraction, consists of the addition of 50 ml sodium pyrophosphate to the sample. After this, the cylinder is made-up to volume (1000 ml) with dilution water and the sample is stirred. Then the sample is allowed to settle for several hours. The different soil fractions will settle at different speeds, i.e small stones and sand will settle faster then clay. This settling time is usually between 4 and 8 hours, so transferring a fraction will generally happen outside working hours. At a specific time and depth in the cylinder during the settling-process, a portion of the sample is taken and transferred into an evaporation dish. The water is evaporated and the remaining soil fraction is the clay fraction of the original soil sample.



This procedure is very labor-intensive and lengthy, especially since the settling time of the sample has to be very accurate. Therefore timing in this manual procedure is very critical, which makes it rather complex and time-consuming.

Skalar has developed a concept to automate the determination of the clay fraction with the SP1000 Robotic Analyzer. This provides a walk-away solution and includes the automation of the addition of sodium pyrophosphate, dilution water, transfer of a small portion of the sample and heating. Controlled by the WindowsTM based software, all actions are programmed to be carried out at accurate time intervals, which can be pre-set. Not only the clay fraction can be determined, but also other fractions (16 µm or 32 µm) can be measured. This once again shows the flexibility, which can be offered on the SP1000 unit.



If you require more information about the automation of Clay Fraction analysis with the Skalar SP1000 Robotic Analyzer or if you want to know if your analytical procedure can be automated, please contact Skalar.

For more information on the Skalar Robotic Analyzers or other Skalar products, please contact Skalar Analytical BV