GOST 20580.3-80
GOST 20580.3−80 (ST SEV 908−78) Lead. Method for the determination of zinc (with Amendments No. 1, 2)
GOST 20580.3−80*
(ST CMEA 908−78)
Group B59
STATE STANDARD OF THE USSR
LEAD
Method of determining zinc
Lead. Method for the determination of zinc
AXTU 1709**
________________
** Changed revision, Rev. N 2.
Date of introduction 1980−12−01
Resolution of the USSR State Committee for standards, dated April 29, 1980, N 1976 the period of validity set with 01.12.80
Proven in 1983 by the Decree of Gosstandart from
________________
** Expiration removed by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (I & C N 11, 1995). — Note the manufacturer’s database.
REPLACE GOST 20580.3−75
* REPRINT December 1984, Change No. 1, approved in December 1983 (ICS 4−84)
The Change N 2, approved and put in force by the Decision of Gosstandart of the USSR from
Change No. 2 made by the manufacturer of the database in the text IUS N 11, 1990
This standard sets the polarographic method for the determination of zinc from 0.0005 to 0.1% lead (99,992−99,5%).
The method is based on dissolution of lead in nitric acid, deposition it in the form of sulphate and polarographically zinc in the ammonia medium in the range of potentials from minus 1.0 to minus 1.8 V relative to the saturated calomel electrode.
The standard fully complies ST SEV 908−78.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis and security requirements — according to GOST 20580.0−80.
(Changed edition, Rev. N 2).
1.2. (Deleted, Rev. N 2).
2. APPARATUS, REAGENTS AND SOLUTIONS
Polarograph polarograph oscilloscope or AC of any type.
Quartz flask with a capacity of 250 cmaccording to GOST 19908−80*.
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* Standards 19908−90. — Note the manufacturer’s database.
Nitric acid GOST 4461−77 diluted 1:3.
Sulfuric acid GOST 4204−77 and diluted 1:1 and 1:48.
Hydrochloric acid by the GOST 3118−77 and diluted 1:1.
Ammonia water according to GOST 3760−79.
Congo red.
Sanitarily sodium (sodium sulfite) crystal on the other 6−09−5313−87, saturated solution.
Gelatin food according to GOST 11293−78*, a solution with a mass concentration of 10 g/DM, freshly prepared.
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* Valid GOST 11293−89. — Note the manufacturer’s database.
Zinc GOST 3640−79*.
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* Valid GOST 3640−94. — Note the manufacturer’s database.
Mercury GOST 4658−73.
Standard solutions of zinc.
Solution a: 1,000 g of zinc is dissolved by heating in 50 cmof hydrochloric acid (1:1), poured 25 cmof water, stirred, cooled and transferred to a volumetric flask with a capacity of 1 DM. Topped up to the mark with water and mix.
1 cmof the solution contains 1 mg of zinc.
Solution B: in a volumetric flask with a capacity of 500 cmstand 50 cmof solution A, made up to the mark with water and mix.
1 cmof a solution contains 0.1 mg of zinc.
Calibration solutions: six volumetric flasks with a capacity of 100 cmwere taken by pipette or microburette 0,6; 1,0; 2,0; 10,0; 20,0 and 30,0 cmof a solution, pour 10 cmof sulphuric acid (1:1). Neutralize the solutions with aqueous ammonia, Congo red and add an excess of 10 cm. The solutions were cooled, poured in 10 cmsaturated solution of sodium sulfite, 2 cmgelatin in the case of polarographically on the oscilloscope polarography, made up to the mark with water and mix thoroughly.
The calibration solutions contain 0,6; 1,0; 2,0; 10,0; 20,0 and 30,0 mg of zinc in 1 DM.
The shelf life of calibration solutions — 7 days.
(Changed edition, Rev. N 1, 2).
3. ANALYSIS
A portion of lead with a mass of 10.00 g was placed in a conical flask with a capacity of 250 cmand dissolved at 70−80 cmof nitric acid (1:3). The solution was boiled to remove oxides of nitrogen, cooled and transferred to a volumetric flask with a capacity of 250 cm, and then topped to the mark with water and mix thoroughly. Depending on the amount of zinc in a flask with a capacity of 250 cmtaken aliquot part of the solution with mass fraction of zinc from 0.0005 to 0.001% — 100 cm, 0.001 to 0.01% to 50 cm, more than 0.01% to 10 cm.
Aliquot part of the solution is diluted with water to 100 cm, heated to 60−70 °C and poured dropwise 5 cmof sulfuric acid solution (1:1). Solution and the precipitate of sulphate of lead heated to boiling and cooled in running water. The precipitate was filtered off on a tight filter «blue ribbon», washed the flask and the filter with sulfuric acid solution (1:48).
The filtrate and washings evaporated to a volume of 2−3 cm. Wash walls with water and again evaporated until the appearance of fumes of sulphuric anhydride.
The residue is cooled, poured 5−7 cmof water, neutralized with ammonia, Congo red, add 2.5 cmof ammonia in excess, cooled and quantitatively transferred to a volumetric flask with a capacity of 25 cm. Then pour 2.5 cmof a saturated solution of sodium sulfite, 0.5 cmgelatin solution in the case of polarographically on the oscilloscope polarography, made up to the mark with water and mix thoroughly.
The solution of lead is poured into the electrolyser and conduct polarography of zinc in the range of potentials from minus 1.0 to minus 1.8 V (against saturated calomel electrode), the speed of the dripping mercury, 5−6, 4−5 delay with the speed voltage of 0.25−0.5 In/s according to the scheme of the instrument «differential 1−3» on the device-5122. Polarography of zinc with the use of other devices is carried out at optimal operation.
Simultaneously with the solution of lead polarographically conduct calibration and control solutions. To calculate the results of the analysis using calibration solutions of similar wave height to be tested. Allowed to use the addition method.
(Changed edition, Rev. N 2).
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of zinc in percent is calculated by the formula
,
where the wave height of solution of the sample, mm;
— zinc concentration in calibration solution, mg/DM;
the volume of the solution of the sample, cm;
— wave height of the calibration solution;
— the weight of the portion of the sample in aliquotes part,
(Changed edition, Rev. N 1, 2).
4.2. Allowable absolute discrepancies in the results of parallel measurements and the results of the analysis shall not exceed the values given in the table.
Mass fraction of zinc, % |
The allowable divergence of the parallel definitions % |
Permissible discrepancies in the results of the analysis % |
To from 0,0005 0,0010 incl. |
0,0002 |
0,0003 |
SV. 0,0010 «0,0020 « |
0,0003 |
0,0004 |
«0,0020» 0,0050 « |
About 0.0006 |
0,0007 |
«0,0050» 0,0100" |
0,0010 |
0,0013 |
«0,010» 0,040 « |
0,002 |
0,003 |
«0,040» 0,100 « |
0,003 |
0,004 |
(Changed edition, Rev. N 1, 2).