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GB/T 13025.8-2012 English PDF (GBT13025.8-2012)

GB/T 13025.8-2012 English PDF (GBT13025.8-2012)

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GB/T 13025.8-2012: General test method in salt industry -- Determination of sulfate

This Part of GB/T 13025 specifies the method for determination of sulfate in salt products and salt chemical products. This Standard applies to the determination of sulfate in salt products and salt chemical products as well as their raw materials.
GB/T 13025.8-2012
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 71.020.50
X 35
Replacing GB/T 13025.8-1991
General Test Method in Salt Industry ?€?
Determination of Sulfate
ISSUED ON. JUNE 29, 2012
IMPLEMENTED ON. DECEMBER 1, 2012
Issued by. General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Gravimetric Method ... 5
4 Volumetric Method (EDTA Complex Titration Method) ... 7
Foreword
This Standard belongs to a complete group of general test methods in salt industry; the complete group comprises the following 13 parts at present; and other test method standards will be developed in the future, if necessary.
-- GB/T 13025.1 General Test Method in Salt Industry ?€? Determination of Grain Size
-- GB/T 13025.2 General Test Method in Salt Industry ?€? Determination of Whiteness
-- GB/T 13025.3 General Test Method in Salt Industry ?€? Determination of Moisture -- GB/T 13025.4 General Test Method in Salt Industry ?€? Determination of Insoluble Matter
-- GB/T 13025.5 General Test Method in Salt Industry ?€? Determination of Chloride Ion
-- GB/T 13025.6 General Test Method in Salt Industry ?€? Determination of Calcium And Magnesium
-- GB/T 13025.7 General Test Method in Salt Industry ?€? Determination of Iodine -- GB/T 13025.8 General Test Method in Salt Industry ?€? Determination of Sulfate -- GB/T 13025.9 General Test Method in Salt Industry ?€? Determination of Lead -- GB/T 13025.10 General Test Method in Salt Industry ?€? Determination of Ferrocyanide
-- GB/T 13025.11 General Test Method in Salt Industry ?€? Determination of Fluoride -- GB/T 13025.12 General Test Method in Salt Industry ?€? Determination of Barium -- GB/T 13025.13 General Test Method in Salt Industry ?€? Determination of Arsenic This Standard is the 8th part of GB/T 13025.
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009. This Standard replaces GB/T 13025.8-1991, General Test Method in Salt Industry - Determination of Sulfate Ion. Compared with GB/T 13025.8-1991, the main technical differences of this Standard, except editorial modifications, are as follows. -- it cancels the photometric analysis method.
This Standard was proposed by China National Light Industry Council and shall be General Test Method in Salt Industry ?€?
Determination of Sulfate
1 Scope
This Part of GB/T 13025 specifies the method for determination of sulfate in salt products and salt chemical products.
This Standard applies to the determination of sulfate in salt products and salt chemical products as well as their raw materials.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition dated applies to this document. For undated references, the latest edition of the referenced document (including any amendments) applies to this Standard.
GB/T 6682-2008 Water for Analytical Laboratory Use ?€? Specification and Test Methods
3 Gravimetric Method
3.1 Principle
Adjust the sample solution to acidity; add barium chloride solution to form barium sulfate precipitation; filter, wash, dry and weigh the precipitate; and calculate the content of sulfate.
3.2 Reagents
3.2.1 Specifications of reagents
Unless otherwise specified, only reagents identified as Analytical Grade and Grade 3 water as specified in GB/T 6682-2008 are used in the analysis.
3.2.2 Hydrochloric acid solution (2 mol/L)
Measure 24 mL of concentrated hydrochloric acid; use water to dilute to 100 mL. 3.2.3 Barium chloride solution (0.02 mol/L)
Weigh 2.40 g of barium chloride; dissolve in 500 mL of water; store at room temperature for 24 h; filter before use.
c(ZnO) ?€? concentration of ZnO standard solution, in mol/L;
V1 ?€? volume of ZnO standard solution absorbed, in mL; and
V2 ?€? amount of EDTA standard titration solution consumed, in mL.
4.2.7 Barium chloride standard solution
Preparation. the same as 3.2.3.
Standardization. draw 5.00 mL of barium chloride standard solution (4.2.7); store in a 150 mL beaker; add 5 mL of ethylenediaminetetraacetic acid disodium magnesium salt hydrate (Mg-EDTA) solution (4.2.4), 10 mL of absolute ethanol, 5 mL of ammonia- ammonium chloride buffer solution and 4 drops of eriochrome black T indicator; use EDTA standard titration solution (4.2.6) for titration until the solution turns from wine red to bright blue; record the volume of EDTA standard titration solution consumed, V1. 4.2.8 Eriochrome black T indicator
Weigh 0.2 g of eriochrome black T and 2 g of hydroxylamine hydrochloride; dissolve in absolute ethanol; use absolute ethanol to dilute to 100 mL; store in a brown bottle. 4.3 Apparatus
General laboratory apparatus.
4.4 Analytical procedure
4.4.1 Preparation
Weigh 25 g of sample crushed to below 2 mm (it is not necessary to crush magnesium chloride samples), accurate to 0.001 g; place into a 400 mL beaker; add 200 mL of water. Heat to nearly boiling until the sample is completely dissolved; transfer to a 500 mL volumetric flask after cooling; add water to dilute to scale before shaking up; and filter if necessary. When the content of the substance to be tested in the sample is too high, it can be diluted properly and then measured.
4.4.2 Draw a certain volume (containing sulfate below 18 mg) of sample solution (4.4.1); place in a 150 mL beaker; add 1 drop of hydrochloric acid solution (4.2.2); add 5.00 mL of barium chloride solution (or add 10.00 mL of barium chloride standard solution when the amount of sulfate is more than 8 mg); stir on a stirrer for a moment; store for 5 min; add 5 mL or 10 mL of Mg-EDTA solution (the same as the volume of barium chloride standard solution added), 10 mL or 15 mL of absolute ethanol (approximately 30% of the total volume), 5 mL of ammonia-ammonium chloride buffer solution and 4 drops of eriochrome black T indicator; use EDTA standard titration solution to titrate until the solution turns from wine red to bright blue; and record the volume of EDTA standard titration solution consumed, V3.
Draw the sample solution of the same volume as that of sulfate tested; store in a 150

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