Interpretation Of New Standard For Determination Of &Nbsp Value Of Textiles And Ph Value Of Aqueous Extracts
1, foreword
National standard
GB/T7573-2009, the determination of pH value of textile water extraction fluid, mainly refers to ISO3071:2005's "determination of the value of textile water extract liquid". The major technical contents have been adjusted. Compared with GB/T7573-2002, the main amendments are as follows: (1) increase the KCl (0.1mol/L) extraction medium; (2) the pH value range of distilled water or deionized water is changed to 5 to 7.5; (3) add a standard buffer solution; (4) change the accuracy requirements of some experimental instruments; (5) the time of oscillation extraction is changed from 1H to 2H + 5min; (6) the requirement of parallel error should not exceed 0.2; (7) the requirement of humidity control of samples is eliminated (7). (ISO3071:2005)
This article mainly aims at (1), (2), (5), (7) modification part to carry out experimental analysis and explore more scientific and reasonable technical conditions.
2. Experiment part
Part of this experiment
Basis
GB/T7573-2009 the implementation plan of the determination of pH value of textile water extraction solution. In view of the technical part of the new standard, the influence of 0.1mol/L KCl extraction medium, extraction time, experimental water, test time, sample humidity control and other factors on the determination of pH value of water extraction solution is emphatically discussed, so as to find the best way for testing and analysis in modern textile laboratory.
In addition to comparing the technical conditions of the experimental part, all other technical conditions of the experiment are carried out in accordance with GB/T7573-2009, without special explanation.
2.1 the influence of extraction medium and extraction time
2.1.1 grade three water (5 to 7.5)
[1]
Extraction medium
Principle: water is a very weak electrolyte, and its ionization equation can be expressed as: H
Two
O H
+
+OH
-
The ion extremely limited, the ionic strength is small, the conductivity of the solution is low, the electrical conductivity of the three level water in the laboratory for the preparation of the water extraction liquid in the textile is generally 2~5 S/cm, the resistance of the water extraction liquid is very high, and it is not negligible compared with the other resistance of the measurement circuit. At the same time, the fluctuation of the liquid junction potential causes the change of the indication of the value of the liquid, which leads to the large amplitude of the indication drift, thus it is not easy to reproduce the result.
2.1.2 KCl (0.1mol/L) extraction
medium
Principle: KCl solution is a typical neutral solution, strong acid and strong base salt, completely ionized in water, K
+
And Cl
-
Will not change H in water
+
The concentration is H
Two
O H
+
+OH
-
The ionization equilibrium will not be destroyed, so the KCl solution will not interfere with the pH value of the test solution itself. It can be used as an ionic strength regulator to increase ionic strength and enhance electrical conductivity, so as to enhance the stability of pH value.
[2]
。
2.1.3 experimental results and analysis
Table 1:
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