1、BSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06Leather - Chemical tests - Determination of pH and difference figureBS EN ISO 4045:2018National forewordThis British Standard is the UK implementation of EN ISO 4045:2018. It is identical to ISO 4045:2018. It supersedes
2、 BS EN ISO 4045:2008, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee TCI/69, Footwear 5.1 and 6.1 have been revised; Clause 7 has been revised: two samples are only prepared when there is enough leather; 8.1 has been revised to more clearly explain th
3、e procedure; 8.2 has been added (previously part of the next clause); 8.3 and 8.4 (previously 8.2 and 8.3) have been revised and the previous title of 8.4 deleted; Clause 9 b) and d) have been revised.iv ISO 2018 All rights reservedBS EN ISO 4045:2018Leather - Chemical tests - Determination of pH an
4、d difference figure1 ScopeThis 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 referencesThe following documents are referred to in the text in such a way that some or all of their
5、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 locationIS
6、O 3696, Water for analytical laboratory use Specification and test methodsISO 4044, Leather Chemical tests Preparation of chemical test samples3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.ISO and IEC maintain terminological databases for use in
7、standardization at the following addresses: ISO Online browsing platform: available at https:/www.iso.org/obp IEC Electropedia: available at http:/www.electropedia.org/3.1difference figuredifference between the pH value of a solution and that of its tenfold dilutionNote 1 to entry: The difference fi
8、gure 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 differe
9、nce 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 PrinciplePreparation 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
10、 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 Reagents5.1 Water, minimum grade 3 in accordance with ISO 3696.INTERNATIONAL STANDARDISO 4045:2018(E) ISO 2018 All rights reserved 1BS EN ISO 4045:2018ISO 4045:20185.2 Buffer
11、solution, for calibrating the electrode system.It is preferable to purchase a commercially available standard buffer solution for measurement as recommended by the pH meter manufacturer. The length of time for which buffer solutions will keep depends on their composition and the method of use. Contr
12、ol of the accuracy of the buffer solution is therefore indispensable. Used buffer solution shall be discarded.6 Apparatus6.1 Suitable shaker, rotating shaker with a frequency of (50 10) r/min or other suitable shaker after validation.6.2 pH meter, with glass electrode, with a measuring range of 0 pH
13、 units to 14 pH units, graduated in 0,01 pH units. The electrode system shall be calibrated prior to each series of measurements against the buffer solution (5.2).Aqueous extracts of heavily fat-liquored leather may in time make the electrode membrane dirty. In such cases, the membrane shall be ligh
14、tly rubbed with a piece of cotton wool dipped in acetone or the electrode should be suspended in a 1:1 water:acetone mixture. After cleaning, the membrane should again be thoroughly soaked in water.6.3 Analytical balance, capable of weighing to an accuracy of 0,01 g.6.4 Wide mouthed flask, with leak
15、-proof stopper, capacity 250 ml.6.5 Measuring cylinder, capacity 100 ml, graduated in 1 ml divisions.6.6 Volumetric flask, capacity 100 ml.6.7 Pipette, capacity 10 ml.7 Sampling and preparation of the samplesSample in accordance with ISO 2418. If sampling in accordance with ISO 2418 is not possible,
16、 then details about sampling shall be given in the test report. Prepare the leather sample in accordance with ISO 4044.Samples should be analysed in duplicate, if it is possible.8 Procedure8.1 Preparation of the extractWeigh (5,0 0,1) g of the test sample into the wide-mouthed flask (6.4) and using
17、the measuring cylinder (6.5) add (100 1) ml of water (5.1) at (20 2) C. Shake well by hand for about 30 s so that the test portion is uniformly wet. Shake mechanically in the shaker (6.1) for between 6,0 h and 6,5 h. Allow the extract to settle. Decant and take the liquid phase for pH measurement, e
18、nsuring that there are no suspended solids.If difficulty is experienced in decanting the extract from the slurry, it may be strained through a clean, dry, non-absorbent mesh (for example, nylon cloth or a coarse sintered glass filter) or centrifuged.2 ISO 2018 All rights reservedBS EN ISO 4045:2018I
19、SO 4045:20188.2 Calibration of the pH meterCalibrate 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
20、.8.3 Determination of the pH valueEnsure that the extract (8.1) is at (20 2) C. Immediately after stirring, immerse the electrode in the extract solution and determine the pH value with the pH meter (6.2), to the nearest 0,05 pH unit, as soon as a steady reading has been reached. The reading should
21、be taken within 30 s to 60 s.The result of the pH value is either the mean value of the two individual determinations, or the value for a single sample.The figures shall be given to the nearest 0,05 pH unit.8.4 Determination of the difference figureIf the pH value is below 4,00 or over 10,00, the di
22、fference figure shall be determined, except if precluded by the client or specification. For this determination, using the pipette (6.7), transfer 10 ml of the extract solution into the volumetric flask (6.6) and fill up to the mark with water (5.1). Rinse the electrodes with approximately 20 ml of
23、the diluted solution and then measure the pH value, as in 8.3.The result of the difference figure value is either the mean value of the two individual determinations, or the value for a single sample.The figures shall be given to the nearest 0,05 pH unit.The difference figure is calculated by subtra
24、cting the pH value obtained in 8.4 from that obtained in 8.3. The difference figure result is quoted to the nearest 0,05 pH unit.9 Test reportThe test report shall include the following:a) a reference to this document (i.e. ISO 4045);b) a description of the sample;c) a reference to any instability o
25、f the pH reading of the extract which prevents an unequivocal statement of the pH value or difference figure;d) pH and, if requested, difference figures as measured in 8.3 and 8.4;e) details of any deviations from the prescribed test conditions. ISO 2018 All rights reserved 3BS EN ISO 4045:2018This
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