EN 13038:2011 – Soil improvers and growing media – Determination of electrical conductivity
1 Scope
This European Standard specifies an instrumental method for the routine determination of electrical conductivity in a water extract of a soil improver or growing medium. The determination is carried out to obtain an indication of the content of water soluble electrolytes in either soil improvers or growing media.
This method is not applicable to liming materials and preformed materials such as mineral wool slabs and foam slabs.
NOTE The requirements of the standard may differ from the national legal requirements for the declaration of the products concerned.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
EN 13040:2007, Soil improvers and growing media – Sample preparation for chemical and physical tests,determination of dry matter content, moisture content and laboratory compacted bulk density
EN ISO 3696, Water for analytical laboratory use – Specification and test methods (ISO 3696:1987)
ISO 1770, Solid-stem general purposes thermometers
3 Terms and definitions
For the purposes of this document the terms and definitions given in EN 13040:2007 and the following apply.
3.1
electrical conductivity
ability of an aqueous extract of the sample to conduct electricity as a function of the ion concentration
4 Principle
A test portion is extracted with water at (22 ± 3,0) °C in an extraction ratio of 1 : 5 (1 V sample + 5 V water) to dissolve the electrolytes. The specific electrical conductivity of the extract is measured and the result is adjusted to a measurement temperature of 25 °C.
5 Reagents
5.1 Water having an electrical conductivity not higher than 0,2 mS/m at 25 °C and a pH >5,6 (grade 2 water according to EN ISO 3696).
5.2 Potassium chloride solution, c(KCl) = 0,100 mol/l
Dissolve 7,456 g potassium chloride, (KCl), previously dried for 2 h at 105 °C, in water (see 5.1) and dilute to 1000 ml. The specific electrical conductivity of this solution at 25 °C is 1290 mS/m.
5.3 Potassium chloride solution, c(KCl) = 0,0100 mol/l
Add 100,0 ml of potassium chloride solution (see 5.2) into a 1000 ml volumetric flask and dilute to the mark with water (see 5.1) at 20 °C. The specific electrical conductivity of this solution at 25 °C is 141 mS/m.
Commercially available solutions may also be used.
NOTE All potassium chloride solutions used for calibration should be stored in tightly sealed glass bottles which do not release alkali metal or alkali earth cations.
6 Apparatus
6.1 Conductivity meter fitted with a conductivity cell and equipped with adjustable measuring range setting and (automatic) temperature correction and having a resolution not greater than 1 mS/m at 25 °C. Preferably, the conductivity meter should also be equipped with a cell constant control.
EN 13038:2011 – Soil improvers and growing media – Determination of electrical conductivity