ISO 3071:2020 pdf download.Textiles – Determination of pH of aqueous extract.
6 Apparatus
6.1 Stoppered glass or polypropylene flasks, chemically resistant, for preparation of the aqueous extract.It is recommended that the glassware used for this test be set aside for this purpose only.
6.2 Mechanical shaker, providing rotational or reciprocating movement sufficient to obtain a ready exchange of liquid between the interior of the textile material and the solution used in preparing the extract. A to-and-fro movement at a rate of 60 r/min or a rotational frequency of 30 r/min has been found satisfactory.
6.3 Beakers, chemically resistant, with a capacity of 150 ml (see ii).
6.4 Rods, chemically resistant (see ii).
6.5 pH-meter, with a glass electrode, with a resolution of at least 0,01 pH-units. A pH-meter with temperature compensation is recommended.
6.6 Balance, with a resolution of at least 0,01 g.
6.7 1 1 volumetric flasks, of grade A quality.
7 Preparation of test specimens
Take a laboratory test sample representative of the bulk of the textile material and sufficient to provide all the test specimens required. Cut the laboratory test sample into pieces having approximately 5 mm sides or of such a size as to allow the test specimens to wet out rapidly.
To avoid contamination, handle the material as little as possible. Take from the laboratory test sample two test specimens of (2,00 ± 0,05) g each.
8 Procedure
8.1 Preparation of the aqueous extract
Prepare the extract of each test specimen at room temperature as follows.
Place each test specimen and 100 ml of extracting solution [potassium chloride solution (5.2)] into a stoppered flask (i). Agitate the flask for a short period by hand to ensure that the textile material is properly wetted out, then shake it mechanically (f2) for 2 h ± 5 mm.
8.2 Measurement of the pH of the aqueous extract
Record the temperature of the extracting solution used.
Calibrate the pH-meter, according to the manufacturer instructions, at the temperature of the extract to be measured. Check the calibration of the pH-meter using two buffer solutions.
Immerse the electrode several times in the KC1 solution used to prepare the extract until the indicated pH-value stabilizes.
Decant a portion of the first extract into a beaker, immediately immerse the electrode to a depth of at least 10 mm and stir gently with a rod until the pH-value stabilizes (do not record the pH-value of this solution).
Decant the remaining first into another beaker, immediately immerse the electrode, without washing, in the beaker to a depth of at least 10 mm and allow to stand without stirring until the pH-value stabilizes. Record this value as the first measurement.
Decant the second extract into another beaker, immediately immerse the electrode, without washing, in the beaker to a depth of at least 10 mm and allow to stand without stirring until the pH-value stabilizes. Record this value as the second measurement.
9 Calculation
If the difference between the two pH-values, expressed to the nearest 0,1 pH-units, is greater than 0,2, repeat the procedure with other test specimens. When two valid measurements have been obtained, calculate the mean value.
10 Precision
Interlaboratory trials were carried out between nine laboratories measuring seven samples. Statistical analysis was carried out and the following result was obtained:
Using KCI solution (52) as the extracting solution: Reproducibility limit R = 1,1 pH-units. NOTE The statistical analysis was carried out in accordance with ISO 5725-2.
11 Test report
The test report shall include the following in formation:
a) a reference to this document, i.e. ISO 307 1:2020;
b) the mean pH-value, to the nearest 0,1 pH-units;
c) the pH of the extracting solution;
d) the temperature of the extracting solution;
e) any factor likely to have had an effect on the results, including any resistance to wetting out of the test samples;
f) the date of the test.ISO 3071 pdf download.