GOST 13938.5-78
GOST 13938.5−78 Copper. Methods for determination of zinc (with Amendments No. 1, 2, 3, 4)
GOST 13938.5−78
Group B59
INTERSTATE STANDARD
COPPER
Methods for determination of zinc
Copper. Methods for determination of zinc
AXTU 1709
Date of introduction 1979−01−01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of nonferrous metallurgy of the USSR
DEVELOPERS
G. P. Giganov, E. M. Peneva, A. A. Blyahman, E. D. Shuvalov, A. N. Savelieva
2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from
3. REPLACE GOST 13938.5−68
4. The standard corresponds to the international standard ISO 4740−85
5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
6. Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 5−6-93)
7. REPRINT (November 1999) with Amendments No. 1, 2, 3, 4, approved in March 1979, April 1983, June 1985, April 1988 (IUS 5−79, 7 to 83, 8−85, 7−88)
This standard specifies the polarographic and atomic absorption methods for the determination of zinc in copper grades according to GOST 859*, except M00k and M00b (with mass fraction of zinc from 0.0005 to 0,006%).
_______________
* On the territory of the Russian Federation GOST 859−2001, here and hereafter. — Note the manufacturer’s database.
(Changed edition, Rev. N 4).
1. GENERAL REQUIREMENTS
General requirements for methods of analysis and safety requirements when performing tests according to GOST 13938.1.
Sec. 1. (Changed edition, Rev. N 4).
2. POLAROGRAPHIC METHOD FOR DETERMINING ZINC
2.1. The essence of the method
The method is based on the polarographic determination of zinc on the background of a 1 M solution of potassium iodide after a preliminary separation of copper by electrolysis.
2.2. Apparatus, reagents and solutions
Polarograph with the applied voltage.
Nitrogen in the cylinder according to GOST 9293.
Water bidistilled.
Ammonium radamisty.
Potassium iodide according to GOST 4232, 5 M solution, freshly prepared: 830 g dissolved in 1 DMof water.
Potassium hydroxide according to GOST 24363, a solution of 200 g/DM.
Nitric acid according to GOST 4461.
Hydrochloric acid according to GOST 3118, diluted 1:1, and the solutions of 0.5 and 2 M.
Mercury GOST 4658.
Utensil to dissolve the sample copper and evaporating the solutions must be of quartz or heat-resistant glass, zinc.
Zinc GOST 3640.
Solutions of the zinc standard.
Solution A, prepared as follows: 1,000 g of zinc is dissolved by weak heating in 15 cmof hydrochloric acid diluted 1:1, pour the solution into volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.
1 cmof the solution contains 1 mg of zinc.
Solution B is prepared as follows: 10 cmof solution A is placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.
1 cmof the solution contains 0.1 mg of zinc.
Solution; prepared as follows: 10 cmof solution B is placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.
1 cmof the solution contains 0.01 mg of zinc.
Solutions B and C were prepared before use.
The zinc standard solutions in volumetric flasks with a capacity of 50 cmmeasured 1,0; 2,0; 3,0 cmV. solution In the fourth flask standard solution is not administered (background). All flasks is poured a solution of potassium hydroxide (200 g/DM). The volume of injected solution of potassium hydroxide should be equal to the volume of solution used in the neutralization of hydrochloric acid eluates when performing analysis of copper.
The solutions were neutralized with 2 n hydrochloric acid to obtain a pH of 1.5−2.0, using as indicator a strip of universal indicator paper. After neutralization poured 10 cmof a solution of potassium iodide, the solution is topped up to the mark with water and mix. Solutions contain 0,2; 0,4; 0,6 mg/kg DMzinc (prepared immediately before polarographically).
Universal indicator paper.
Methyl orange indicator solution 1 g/DM.
Phenolphthalein (the indicator) at the NTD, solution in alcohol 1 g/DM.
Copper according to the GOST 859.
Installation for electrolysis with a platinum mesh electrode according to GOST 6563.
The mixture of acids to dissolve: mix 100 cmof sulphuric acid and 250 cmof water, after cooling, add 70 cmof nitric acid.
Allowed the use of other reagents, subject to obtaining the metrological characteristics are not inferior to those specified in the standard.
2.1, 2.2. (Changed edition, Rev. N 2, 4).
2.3. Analysis
2.3.1. A sample of copper with a mass of 2.0 g was placed in a beaker with a capacity of 200−250 cm, 20−25 cm, pour themixture of acids to dissolve, cover the beaker with a cover glass and heated to dissolve the sample, removal of the bulk of the nitrogen oxides. Remove the glass, wash it with water over a Cup, the Cup poured 100−150 cmof water and heated solution to a temperature of 40−50 °C. Immerse in a solution of a platinum mesh electrodes and conduct electrolysis at a current density of 2−3 A/DMand a voltage of 2−2,5 In, stirring the solution with a stirrer. When in solution will remain 200−300 mg of copper to establish a comparison with a previously prepared solution of copper, electrolysis is stopped.
The cathodes are removed, washed 2−3 times with water, the electrolyte is heated and then evaporated to wet salts. Pour 20−30cmof water, heated to dissolve the salts, cooled and placed in a volumetric flask with a capacity of 50 cm. Add 10 cmof a solution of potassium iodide, dilute to the mark with water and mix. In a vessel for passing gas placed part of the solution and flow nitrogen for 10−15 min.
The solution is poured into the cell and polarographic in the range of potentials from minus to minus 0,85 0,45 V. at the same time polarographic solutions in the reference experiment and the standard solutions of zinc.
(Changed edition, Rev. N 4).
3. ATOMIC ABSORPTION METHOD FOR DETERMINING ZINC
3.1. The method is based on dissolving the samples in nitric acid and the measurement of atomic absorption of zinc in the flame acetylene-air.
(Changed edition, Rev. N 4).
3.2. Apparatus, reagents and solutions
Spectrophotometer, atomic absorption, comprising a lamp with a zinc hollow cathode burner flame acetylene-air or propane-butane-air and spray system.
Acetylene according to GOST 5457.
Propane-butane according to GOST 20448.
Air compressor.
Water bidistilled.
Nitric acid, OS.CH., according to GOST 11125, diluted 1:1, or nitric acid according to GOST 4461 (boiled to remove oxides of nitrogen).
Copper according to the GOST 859.
Zinc GOST 3640.
Solutions of the zinc standard.
Solution A, prepared as follows: 0,100 g of zinc is dissolved in 10 cmof nitric acid, diluted 1:1, the solution was transferred to volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.
1 cmof the solution contains 0.1 mg of zinc.
Solution B is prepared as follows: 10 cmof solution A is placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.
1 cmof the solution contains 0.01 mg of zinc.
(Changed edition, Rev. N 2, 4).
3.3. Analysis
3.3.1. A sample of copper with a mass of 1.0 g was placed in a beaker with a capacity of 100 cmand dissolved in 10 cmof nitric acid solution to remove oxides of nitrogen. Cool the solution and placed in a volumetric flask with a capacity of 100 cm, is diluted to the mark with water. The resulting copper solution sprayed into the flame of atomic absorption spectrophotometer and measure the absorbance in the flame at a wavelength of 213,8 nm.
In the solution of the sample allowed the determination of Nickel (from 0.1 to 0.5%), lead (from 0.005 to 0.06%), iron (0.01 to 0.08%) and cobalt (0.005 to 0.2%).
At the same time conducting follow-up experience with all the applied reagents. The value of the optical density of the solution in the reference experiment is subtracted from the value of the optical density of the analyzed solution.
The mass of zinc in the solution is determined by the calibration schedule.
Allowed to determine the mass fraction of zinc to use the addition method.
(Changed edition, Rev. N 2, 4).
3.3.2. Building a graded graphics
To build a calibration curve in five out of six volumetric flasks with a capacity of 100 cmis placed 0,5; 1,0; 2,0; 4,0 and 6,0 cmstandard solution B. In all flasks add 2cmof a solution of nitric acid, dilute to the mark with water and mix.
Measure the absorbance of the solutions prepared as described in section
According to the obtained values of optical density of solutions and the corresponding content of zinc build a calibration curve. When plotting the signal values of the background solution is subtracted from the signal values of each standard solution and carry out the schedule from the origin.
(Changed edition, Rev. N 4).
3.3.3. Allow the definition of zinc from the chloride solutions.
(Added, Rev. N 4).
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of zinc () in the percentage polarographic determination calculated by the formula
,
where the wave height of the zinc obtained with the test solution polarographically, minus the height of the waves in the reference experiment, mm.
— the volume of the analyzed solution, cm;
— weight of copper corresponding to aliquote part of the solution, taken for polarographically, g;
the value of the ratio of the wave height of the zinc standard solution by its concentration, mm/mg/DM.
The value for the selected sensitivity of the instrument find, polarography two standard solution (similar concentration of zinc and its concentration in the sample solution) in the same interval of potentials, and calculated by the formula
,
where , ,
where , — concentration of standard solutions, mg/DM;
— height of waves, obtained by polarography standard solutions minus the height of the wave solution of the background.
4.2. Mass fraction of zinc () while atomic-absorption determination is calculated by the formula
,
where is the mass of zinc in the sample solution found by the calibration schedule, mg;
— weight of copper,
4.3. Discrepancies in the results of two parallel measurements and the two tests should not exceed the values given in the table.
4.2, 4.3. (Changed edition, Rev. N 4).
4.4. The differences in the evaluation of the mass fraction of the zinc used atomic absorption method.
(Added, Rev. N 4).
APP. (Deleted, Rev. N 4).