GB/T 5211.13-1986 Determination of pH value of aqueous pigment extracts GB/T5211.13-1986 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of acidity or alkalinity of the aqueous extract of pigments
UDC 667.622
GB 5211.13-86Www.bzxZ.net
This standard specifies the general test method for determining the acidity or alkalinity of the aqueous extract of pigments samples. This standard is equivalent to the international standard ISO787/4-1981 "General test methods for pigments and extenders-Part 4: Determination of acidity and alkalinity of aqueous extracts".
Note: When this general method is applicable to a specified pigment or extender, it is only necessary to include a reference to this method in the product standard of the pigment or extender, and indicate the changes required due to the characteristics of the product. Only when this general method is not applicable to a specific product, a special method should be specified to determine the acidity and alkalinity.
1 Reagents
All reagents used are analytically pure. Use distilled water or water with the same purity as distilled water. 1.1 Hydrochloric acid standard solution, 0.05mol/L. 1.2 Sodium hydroxide standard solution, 0.05mol/L. Or potassium hydroxide standard solution, 0.05mol/L. 1.3 Methyl red indicator, 1g/L, 60% (V/V) ethanol solution. 2 Instruments
In addition to conventional laboratory instruments, the following instruments are required. 2.1 Burette, capacity of 50ml.
2.2 pH measuring device, capable of measuring to o.1 unit, calibrated with a buffer solution of known pH at the test temperature. 3 Test steps
Two samples need to be measured in parallel.
3.1 Test solution
Perform the operation specified in GB5211.2-85 "Determination of water-soluble pigments by thermal extraction method", and the sample size shall be in accordance with the product standard.
Note: If specified or agreed upon, the operation may be carried out in accordance with GB5211.1-85 "Determination of Water-soluble Pigments by Cold Extraction Method". In this case, the stirring time should be reduced to 5 min.
3.2 Determination
3.2.1 Indicator Method
Add 5 drops of red indicator (1.3) to 100 ml of the test solution (3.1). If the solution is orange, it is considered to be neutral. If the solution is yellow (alkaline), titrate with hydrochloric acid solution (1.1) until the color turns orange as the endpoint. If the solution is red (acidic), titrate with sodium hydroxide or potassium hydroxide solution (1.2) until the color turns orange as the endpoint. Note: Another indicator may be used upon agreement between the parties concerned. ② If the filtrate is colored, the indicator method (3.2.1) should not be used, and the potentiometric titration method (3.2.2) should be used. 3.2.2 Potentiometric titration
Insert the electrode of the pH measuring device into 100 ml of the test solution (3.1) and read the pH value. Issued by the National Bureau of Standards on August 26, 1986
Implemented on August 1, 1987
GB 5211.13-86
If the pH value is between 4 and 8, the solution is considered neutral. If the pH value is greater than 8 (alkaline), titrate with hydrochloric acid solution (1.1) to just less than 8. If the pH value is less than 4 (acidic), titrate with sodium hydroxide or potassium hydroxide solution (1.2) to just greater than 4. 3.2.3 Repeat determination
If the difference between the results of the two parallel samples exceeds 5% of the higher value, repeat the test procedure (Chapter 3). Result expression
Calculate the acidity (alkalinity) according to the following formula:
A = 125 ×
武t:A
-acidity (alkalinity), expressed in milliliters of 0.1 mol/L alkali (hydrochloric acid) solution required to neutralize 100 g of the product extract,
-mass of sample taken to prepare the test solution (3.1), g; volume of sodium hydroxide, potassium hydroxide solution (1.2) or hydrochloric acid solution (1.1), ml. V
Report the average of two determinations.
If the extract is neutral, report the result as "neutral". 5
Test report
The test report shall at least include the following contents: the type and name of the test pigment,
whether the test solution is prepared by cold extraction or hot extraction; whether the indicator method or potentiometric titration method is used, the test results expressed in Chapter 4,
the difference from the operation specified in this test,
the test date.
Additional notes:
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China and is under the jurisdiction of the National Technical Committee for Standardization of Paints and Pigments. This standard was drafted by the 15th Working Group of the Standard Technical Committee for Pigment Inspection Methods. The main drafters of this standard are Suo Yunxia and Ji Jun. 1208
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