GB/T 33948.2-2017 English PDF (GBT33948.2-2017)

This Part of GB/T 33948 specifies the determination method of zinc content of copper-steel composite metal. This Part applies to the determination of zinc content of copper-steel composite metal. The determination range is 0.50% ~ 6.50%.

GB/T 33948.2-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.120.30
H 13
Method for chemical analysis of copper-steel
composite metal - Part 2. Determination of zinc
content - Na2EDTA titration method
ISSUED ON. JULY 12, 2017
IMPLEMENTED ON. FEBRUARY 1, 2018
Issued by. General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration Committee.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Method summary ... 4
3 Reagents ... 4
4 Specimen ... 6
5 Analysis steps ... 6
6 Calculation of analysis results ... 7
7 Precision... 8
8 Test report ... 8
Method for chemical analysis of copper-steel
composite metal - Part 2. Determination of zinc
content - Na2EDTA titration method
1 Scope
This Part of GB/T 33948 specifies the determination method of zinc content of copper-steel composite metal.
This Part applies to the determination of zinc content of copper-steel composite metal. The determination range is >0.50% ~ 6.50%.
2 Method summary
The test material is dissolved in hydrochloric acid. Zinc and thiocyanate form a complex anion in dilute hydrochloric acid medium. After extracting and
removing most of the interference elements with 4-methyl-2-pentanone
extraction, in hexamethyltetramine buffer solution with a pH of 5.5-6.0, add concealer to xylenol orange as indicator, titrate with Na2EDTA standard titration solution until the solution turns from red to yellow. Calculate the amount of zinc based on the volume of Na2EDTA standard solution consumed.
3 Reagents
Unless otherwise stated, only analytically pure reagents and distilled or deionized water or equivalent water are used in the analysis.
3.1 4-methyl-2-pentanone.
3.2 Hydrogen peroxide (ρ=1.11 g/mL).
3.3 Hydrochloric acid (1+1).
3.4 Nitric acid (1+1).
3.5 Ammonium fluoride solution (200 g/L), stored in plastic bottle.
3.6 Thiourea Solution (100 g/L).
3.7 Ammonium thiocyanate solution (500 g/L).
V0 - the volume of Na2EDTA titration solution consumed when titrating a blank solution, in milliliters (mL);
63.55 - mole mass of zinc, in grams per mole (g/mol).
3.12.3 Parallel calibration
Perform 3 copies of parallel calibration. The standard volume of Na2EDTA standard titration solution used for calibration is not more than 0.10 mL. Take its average value, otherwise, recalibrate.
4 Specimen
4.1 Wipe clean the surface of the copper-steel composite metal specimen with acetone of thickness less than or equal to 0.7 mm, without oxidation, oil stain. Then make the sample into pieces with a width of no more than 1mm. And
ensure that the coating metal is consistent when preparing double-sided (or single-sided) composite specimen.
4.2 Copper-steel composite metal sample with a thickness greater than 0.7 mm is first made into thin strips with a width of 1 mm. And wipe it clean with acetone, without oxidation, oil stain. Then make it to pieces less than 1 mm in width. And ensure that the coating metal is consistent when preparing double- sided (or single-sided) composite specimen.
5 Analysis steps
5.1 Test material
Weigh 0.200 g of specimen (Clause 4), to the nearest of 0.0001 g.
5.2 Number of determinations
Perform two determinations independently. Take the average value.
5.3 Blank test
Perform the blank test with test materials.
5.4 Determination
5.4.1 Place the test material (5.1) in a 500-mL conical beaker. Add 10 mL of hydrochloric acid (3.3). Drop hydrogen peroxide 4 times (3.2), 2 mL for each (shake for a moment for each adding). Dissolve at low temperature until the sample dissolves completely (solution is transparent without impurities). Cover the watch glass, boil, remove excessive hydrogen peroxide, cool. If the