BS EN ISO 14254 pdf download

BS EN ISO 14254 pdf download Soil quality — Determination of exchangeable acidity in barium chloride extracts (ISO 14254:2001)
1 Scope
This International Standard specifies a method for the determination of exchangeable acidity in barium chloride extracts of soil samples obtained according to ISO 11260. The procedure described herein mainly concerns the determination of total exchangeable acidity by means of a fixed-pH end-point titration (see note).
Two optional procedures are also given, describing respectively, determinations of free H + acidity and of aluminium in the extracts. This International Standard is applicable to all types of air-dry soil samples which have been pretreated in accordance with ISO 11464. NOTE Titration of exchangeable acidity by means of a fixed-pH end-point may not be specific to a given acid species.
The end- point pH value retained is 7,8, corresponding to complete precipitation of Al +3 ions in synthetic solutions.
Titration of soil extracts to this pH may also include some more weakly ionized species or weak acid organic compounds.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.
ISO 3696, Water for analytical laboratory use —Specification and test methods
ISO 11260, Soil quality — Determination of effective cation exchange capacity and base saturation level using barium chloride solution
ISO 11464, Soil quality —Pretreatment of samples for physico-chemical analyses
ISO 11465, Soil quality —Determination of dry matter and water content on a mass basis —Gravimetric method
3 Principle
The soil sample is extracted in accordance with ISO 11260. The extract is titrated with a NaOH solution up to pH = 7,8. The use of phenolphthalein as indicator is allowed, but shall be specified in the test report. An alternative method for determination of the free H + acidity is proposed, in which sodium fluoride is added to the soil extract before the titration (BaF 2 precipitates but an excess of NaF is not necessary).
Aluminium ions are complexed and only the H + acidity is detected during the titration process.
Two other optional methods for the determination of aluminium are proposed, using respectively flame atomic absorption spectrometry and inductively coupled plasma emission spectrometry.