BS EN ISO 4045:2018 pdf download – Leather – Chemical tests – Determination of pH and difference figure This document specifies a method for determining the pH value and the difference figure of an aqueous leather extract. It is applicable to all types of leather. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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. ISO 2418, Leather — Chemical, physical and mechanical and fastness tests — Sampling location ISO 3696, Water for analytical laboratory use — Specification and test methods ISO 4044, Leather — Chemical tests — Preparation of chemical test samples 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https://www.iso.org/obp — IEC Electropedia: available at http://www.electropedia.org/ 3.1 difference figure difference between the pH value of a solution and that of its tenfold dilution Note 1 to entry: The difference figure is a measure of the strength of acids and bases and can never exceed a value of 1. The difference figure amounts to 0,70 to 1,00 when a solution contains a free strong acid (or a free strong base). The ionization of weak acids and bases increases with greater dilution, and therefore the difference figure can only act as a criterion for the presence of free strong acid or base in aqueous extracts with pH values below 4 or above 10. 4 Principle Preparation of an aqueous extract from a test portion of the leather and measurement of the pH of the extract, using a pH meter. In cases where the pH value obtained is below 4,00 or above 10,00, the pH value of a tenfold dilution of the aqueous extract is also determined. 5 Reagents 5.1 Water, minimum grade 3 in accordance with ISO 3696. 8.2 Calibration of the pH meter Calibrate the pH meter with a minimum of two buffer solutions: at least one below the expected value and at least one above the expected value. Both these buffer readings shall be within 0,02 pH units of the correct reading when the pH meter is standardized. 8.3...
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