GB/T 7573-2025Textiles - Determination of pH of aqueous extract (English PDF)

Foreword

This document was drafted in accordance with the provisions of GB/T 1.1-2020

"Directives for standardization - Part 1.Rules for the structure and drafting of

standardizing documents".

This document replaces GB/T 7573-2009 " Textiles - Determination of pH of aqueous

extract". Compared with GB/T 7573-2009, in addition to structural adjustments and

editorial changes, the main technical changes are as follows.

- ADD examples of various textile products "(such as fibers, yarns, fabrics, down

and other fillings)" (see Chapter 1);

- ADD "or directly purchased" (see 5.3);

- DELETE "filled with distilled water when not in use, the same below." (see 6.1 of

the 2009 edition);

- DELETE "6.5 measuring cylinder. 100 mL, chemically stable" (see 6.5 of the 2009

edition);

- CHANGE "measurement accuracy of at least 0.1" to "resolution of at least 0.01 pH

unit" (see 6.5; 6.6 of the 2009 edition);

- ADD "thermometer" (see 6.8);

- ADD the size requirement "or a size that allows the sample to be wetted quickly"

(see 7.1);

- CHANGE "avoid contamination and direct contact with the sample by hand" into

that "avoid contamination of the specimen during specimen preparation";

CHANGE "prepare 3 parallel samples for each test sample" to "prepare 2

specimens for each test sample" (see 7.2; 7.2 of the 2009 edition);

- CHANGE "100 mL of water (5.1) or potassium chloride solution (5.2)" into "100

mL of potassium chloride (KCl) solution (5.2)" (see 8.1; 8.1 of the 2009 edition);

- ADD "If an electrode without temperature compensation is used, use a thermometer

(6.8) to measure and record the temperature of the extract"; CHANGE the three

parallel samples in the test process to 2 specimens. (See 8.2; 8.2 of the 2009 edition);

- DELETE "Using water (5.1) as the extraction medium. Reproducibility limit R =

3696 (see 5.1; 5.1 of ISO 3071.2020) for easy understanding;

- CHANGE the frequency of the mechanical oscillator from "is suitable" to "at least"

(see 6.2; 6.2 of ISO 3071.2020) for easy understanding;

- ADD the thermometer (see 6.8) for easy operation;

- CHANGE that "The pH meter is calibrated with two buffer solutions at the

temperature of the extract" into that "The pH meter is calibrated with two or three

buffer solutions at the temperature of the extract" (see 8.2; 8.2 of ISO 3071.2020),

for easy operation;

- ADD "b) Sample description" to the test report for easier understanding (see

Chapter 11).

1 Scope

This document describes the method for determining the pH value of aqueous extracts

of textiles.

This document is applicable to various textile products (such as fibers, yarns, fabrics,

down and other fillings).

2 Normative references

The contents of the following documents constitute the essential terms of this document

through normative references in the text. Among them, for dated references, only the

version corresponding to that date applies to this document; for undated references, the

latest version (including all amendments) applies to this document.

GB/T 6682 Water for analytical laboratory use - Specification and test methods

(GB/T 6682-2008, ISO 3696.1987, MOD)

3 Terms and definitions

The following terms and definitions apply to this document.

3.1

pH value

The negative logarithm of the hydrogen ion concentration in the aqueous extract.

4 Principle

The pH value of the aqueous extract of the textile is determined at room temperature

using a pH meter with a glass electrode.

5 Reagents

Distilled or deionized water, at least meeting the requirements of GB/T 6682 Grade

3 water, with a pH value within 5.0 ~ 7.5.

6 Instruments

Stoppered glass or polypropylene flask. 250 mL, chemically resistant.

Mechanical oscillator. Capable of rotating or reciprocating to ensure sufficient

liquid exchange between the sample and the extract, with a reciprocating rate of at least

60 times/min and a rotary rate of at least 30 cycles/min.

7 Specimen preparation

Select representative laboratory samples from the batch of large samples, the

number of which shall meet the amount required for all tests.

8 Measurement steps

Prepare the extracts of two specimens at room temperature. Add one set of specimen to

a stoppered flask (6.1); measure 100 mL of potassium chloride (KCl) solution (5.2);

cover the flask tightly; shake it for a while to make the sample completely wet. Place

the flask on a mechanical oscillator (6.2) and oscillate for 2 h ± 5 min.

9 Calculation and expression of results

If the difference between two pH measurement values (accurate to 0.1) is greater than

10 Precision

9 laboratories jointly tested 7 specimens and obtained the following results after

statistical analysis.

Appendix A

Preparation of standard buffer solution

All reagents are analytically pure. The water used to prepare the buffer solution must at

least meet the requirements of GB/T 6682 Grade 3 water; it shall be replaced at least

once a month.

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