GOST 12072.3-79
INTERSTATE STANDARD
CADMIUMMethods for determination of zincCadmium. Methods of zinc determination |
GOST |
Date of introduction 01.12.80
This standard specifies the polarographic and atomic absorption methods for the determination of zinc (at a mass fraction of zinc from 0.0005% to 0.3%). The standard fully complies ST SEV 915−78.
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis and security requirements — according to GOST 12072.0.
(Changed edition, Rev. No. 2).
2. POLAROGRAPHIC METHOD
2.1. The essence of the method
The method is based on extraction of zinc by ether in the form of Rodenstock complex and polarogram-verovanii of zinc on ammonium-ammonia background at the half-wave potential of minus 1.45, against the background of the solution of phosphoric acid at a potential of half-wave minus 1.3 V relative to a saturated calomel electrode.
2.2. Apparatus, materials and reagents
Polarography oscillographic or polarograph AC complete with all accessories.
Hydrochloric acid according to GOST 3118, diluted 1:1 and 1:9.
Nitric acid according to GOST 4461 and diluted 1:1.
Orthophosphoric acid according to GOST 6552, a solution of 0.03 mol/DM3.
Sulfuric acid according to GOST 4204, diluted 1:1, 1:9, and the solution of 0.5 mol/DM3.
Hydrogen peroxide (peroxide) according to GOST 10929.
Ammonia water according to GOST 3760.
Ammonium radamisty according to GOST 27067, a solution of 600 g/DM3.
Ammonium chloride according to GOST 3773.
Sodium sanitarily on the other 6−09−5313.
Ammonia background electrolyte: in a flask with a capacity of 1 DM3 were placed 50 g of ammonium chloride, 20 g of sodium semitecolo, pour 500 cm3 of water, stirred, poured 50 cm3 of ammonia, 10 cm3 of a solution of gelatin, made up to a volume of 1 DM3 with water and mix.
The expiration date of the background electrolyte is 7 days.
Gelatin food according to GOST 11293, solution 5 g/DM3, freshly prepared.
Ammonium undeviatingly meta GOST 9336, saturated solution.
Wash solution: to 100 cm3 of sulfuric acid of 0.5 mol/DM3 added to 25 cm3 of a solution of ammonium Rodenstock and stirred.
Ether ethyl (medical) or the isopropyl ether on the other 6−09−3704.
Nitrogen gas according to GOST 9293. Nitrogen purified from oxygen in the following manner: a stream of nitrogen was passed through three bottles containing at the bottom of the zinc amalgam and filled with a saturated solution of ammonium anadalucia in sulfuric acid solution, diluted 1:9, and previously restored with amalgam of zinc (violet color).
Zinc amalgam: 200 g of zinc was treated in a thick-walled vessel in a mixture containing 10 cm3 of mercury and 50 cm3 of sulphuric acid, diluted 1:9.
Zinc GOST 3640.
Mercury GOST 4658.
Standard solutions of zinc.
Solution a: a sample of zinc with a mass dissolve 0,250 g in a volumetric flask with a capacity of 500 cm3 50 cm3 of hydrochloric acid diluted 1:1, made up to the mark with water and mix.
1 cm3 of solution contains 0.5 mg of zinc.
Solution B: in a volumetric flask with a capacity of 500 cm3 metered pipette 20 cm3 of solution A, pour 50 cm3 of hydrochloric acid diluted 1:1, made up to the mark with water and mix.
1 cm3 of a solution contains 0.02 mg of zinc.
Calibration solutions of zinc (supplements to the standard method of solution): two batches of cadmium metered pipette standard solution of zinc B according to table. 1, pour 10 cm3 of nitric acid, diluted 1:1, heated to dissolution of the sample and evaporated to dryness. Then do as described in section 2.3.
Table 1
| Mark of cadmium | The mass of charge, g | Standard solution | The amount of added standard solution |
Volume volumetric flasks, cm3 | Mass concentration zinc, mg/DM3 | |
| cm3 | mg | |||||
| Кд0А | 1,000 | B | 0,25 | 0,005 | 25 | 0,2 |
| Кд0А | 1,000 | B | 0,5 | 0,01 | 25 | 0,4 |
| Кд0 | 1,000 | B | 1,0 | 0,02 | 25 | 0,8 |
| Кд0 | 1,000 | B | 2,0 | 0,04 | 25 | 1,6 |
| Кд1 | 1,000 | B | 2,5 | 0,05 | 25 | 2,0 |
| Кд1 | 1,000 | B | 3,5 | 0,07 | 25 | 2,8 |
| Кд0С | 1,000 | B | 4,0 | 0,08 | 25 | 3,2 |
| Кд1С | 1,000 | B | 5,0 | 0,1 | 25 | 4,0 |
| Кд2С | 0,200 | And | 0,4 | 0,2 | 50 | 4,0 |
| Кд2С | 0,200 | And | 0,8 | 0,4 | 50 | 8,0 |
| Кд2С | 0,200 | And | 1,2 | 0,6 | 50 | 12,0 |
2.3. Analysis
In a conical flask with a capacity of 250 cm3 put the weight of cadmium weight of 1,000 g, pour 10 cm3 of nitric acid, diluted 1:1, and heated to dryness. Pour 5 cm3 of hydrochloric acid and evaporated to dryness.
To the residue poured in 20 cm3 of sulfuric acid of 0.5 mol/DM3 solution, heated to dissolve the salts, cooled, poured into a separatory funnel with a capacity of 150 cm3, pour 5 cm3 of a solution of ammonium Rodenstock, made up to a volume of 50 cm3 of water, previously was washed flask, where the sample, add 50 cm3 of isopropyl or ethyl ether, and shaken for 2 minutes, the Lower aqueous phase is discarded, and the ether extract washed with 25 cm3 wash solution for 10 s. the Washing of the extract is repeated. The ether extract was transferred to conical flask with a capacity of 100−250 cm —3 and distilled off the ether on a water bath.
To the residue add 2 cm3 of sulfuric acid diluted 1:1, add 5−6 drops of nitric acid and the solution was evaporated to dryness, occasionally adding 2 drops of hydrogen peroxide.
In the determination of zinc on the oscilloscope polarography the residue treated with 2−3 drops of ammonia, pour 10 cm3 background electrolyte, mixed and according to table. 1 transferred quantitatively to the appropriate volumetric flask, made up to the mark and the background electrolyte and stirred. Part of the solution is poured into the polarographic cell and conduct polaro-gravirovani zinc at optimal current range, and half-wave potential of minus 1.45 relative to the saturated calomel electrode. In similar conditions hold polarography calibration solutions of zinc and solutions of control experiments.
In the determination of zinc perimentally polarographic method to the cooled residue is poured 10 cm3 of a solution of phosphoric acid, heat the solution to dissolve the salt, cooled, transferred to a volumetric flask with a capacity of 25 or 50 cm3, pour the solution of phosphoric acid to the mark and mix. Part of the solution is poured into the polarographic cell, purged for 5 min with nitrogen (nitrogen previously passed through a flask with ammonium Vanadate) and spend polarographically with a corresponding current range and the peak capacity minus the 1.25−1.30 In relative to the saturated calomel electrode. In similar conditions hold polarography calibration solutions of zinc and solutions of control experiments.
When calculating the amount of zinc from the value of the wave height of the sample subtract the height of the waves in the reference experiment, and the values of the wave height of the sample with the addition of the wave height of the sample and the reference experiment.
2.1 — 2.3. (Changed edition, Rev. No. 3).
3. ATOMIC ABSORPTION METHOD
3.1. The essence of the method
The method is based on measurement of the absorption of the analytical line of zinc at a wavelength of 213,8 nm with the introduction of solutions of the analyzed sample and calibration solutions in the air-acetylene flame. A portion of the cadmium pre-transferred into solution by acid decomposition.
3.2. Apparatus, materials and reagents
Atomic absorption spectrophotometer any brand with a radiation source for zinc.
Air, compressed under a pressure of 2105-6105 PA (2−6 ATM).
Acetylene in the cylinder.
Nitric acid according to GOST 11125, diluted 1:1 and solution 2 mol/DM3.
Standard solutions of zinc.
Zinc GOST 3640 not below grade C2.
Solution a: a sample of zinc weight 0,100 g were placed in a glass with a capacity of 100 cm3, pour 10 cm3 of a solution of nitric acid, diluted 1:1, heated to remove oxides of nitrogen, cooled, quantitatively transferred to a volumetric flask with a capacity of 1 DM3, made up to the mark with water and mix.
1 cm3 of solution contains 0.1 mg of zinc.
Solution B: 25 cm3 solution And transferred to a volumetric flask with a capacity of 250 cm3, made up to the mark with water and mix.
1 cm3 of solution contains 0.01 mg of zinc.
Cadmium GOST 1467 or GOST 22860 containing zinc of not more than 110-4 %, solution 100 mg/DM3; 100 g of cadmium in the form of pieces or shavings dissolved in 200−250 cm3 of nitric acid. Pour the acid slowly in small portions (about 10 cm3). If you add another portion of acid, the reaction goes slowly, poured the resulting solution of cadmium nitrate to another flask and continue the decomposition. Then combine all the solution, boil to remove oxides of nitrogen, diluted with water, transferred into a measuring flask with volume capacity of 1000 cm3 and mixed.
(Changed edition, Rev. No. 1, 2, 3).
3.3. Analysis
3.3.1. The weight of cadmium weight of 1,000−5,000 grams is placed in a conical flask with a capacity of 250 cm3, poured 15−25 cm3 of nitric acid, diluted 1:1, heated until complete dissolution of the metal and remove oxides of nitrogen. Pour 25 cm3 of water, stirred, cooled, the solution was quantitatively transferred to a volumetric flask with a capacity of 100 cm3 and mix. The solution of the analyzed sample and calibration solutions is injected into air-acetylene flame and measuring the absorption of the analytical line zinc 213,8 nm according to GOST 12072.0.
If necessary, in solution of the sample can be determined also the content of thallium, lead, iron, copper and Nickel.
3.3.2. To build a calibration curve prepared two series of calibration solutions.
I series: in twelve of the thirteen volumetric flasks with a capacity of 100 cm3 metered 2,0; 5,0; 10,0 and 20,0 cm3 of a solution and 4,0; 6,0; 8,0; 10,0; 15,0; 20,0; 25,0 and 30.0 cm3 of solution A (corresponding to 0,2; 0,5; 1,0; 2,0; 4,0; 6,0; 8,0; 10,0; 15,0; 20,0; 25,0; 30,0 mg/DM3, zinc), to each flask pour 10 cm3 of a solution of nitric acid 2 mol/DM3, made up to the mark with water and mix. The basis of these calibration solutions is water.
II series: in four of the five volumetric flasks with a capacity of 100 cm3 metered 2,0; 5,0; 10,0 and 20,0 cm3 of solution B (which corresponds to 0.2, 0.5, 1.0 and 2.0 mg/DM3, zinc); in each flask pour 10 cm3 of a solution of nitric acid 2 mol/DM3, 50 cm3 of a solution of cadmium 100 g/DM3, made up to the mark with water and mix. The basis of these calibration solutions is the solution of cadmium. For the calibration solutions I series measure the sample solution from a sample mass of 1.0−2.5 g II a series of calibration solutions is used for the analysis of the sample solution from a sample weighing 5 g.
In the determination of one solution of iron, lead, thallium, copper and Nickel in each of the above flasks one of a series of calibration solutions add such amounts of standard solutions of the elements that would correspond to their concentrations in the calibration solutions.
3.3.1,
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of zinc (X), %, polarographic determination calculated by the formula
where H is the wave height of zinc in the analyzed sample solution, mm;
V — volume of the volumetric flask, cm3;
h — height of zinc calibration solution;
With — mass concentration of zinc in calibration solution, mg/DM3;
t — the weight of the portion,
(Changed edition, Rev. No. 3).
4.2. Mass fraction of zinc (X), %, atomic absorption determination is calculated by the formula
where With1 — mass concentration of zinc in the sample solution, mg/DM3;
With2 — mass concentration of zinc in solution in the reference experiment, mg/DM3;
t — mass of sample, g;
V — volume of the volumetric flask, cm3.
(Changed edition, Rev. No. 1, 3).
4.3. Allowable absolute discrepancies in the results of parallel measurements and the results of the analysis shall not exceed the values given in table. 2.
Table 2
| Mass fraction of zinc, % | The permissible difference for parallel definitions % | The permissible discrepancy between the results of the analysis % |
| To from 0,0005 0,0010 incl. | 0,0003 | 0,0004 |
| SV. 0,0010 «0,0040 « | 0,0005 | About 0.0006 |
| «0,0040» 0,0100 « | 0,0015 | 0,0020 |
| «0,010» 0,040 « | 0,003 | 0,004 |
| «0,040» 0,100 « | 0,010 | 0,013 |
| «To 0.10» to 0.30 « | 0,02 | 0,03 |
(Changed edition, Rev. No. 3).
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of nonferrous metallurgy of the USSR
2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from
3. The standard fully complies ST SEV 915−78
4. REPLACE GOST 12072.3−71
5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced | The number of the paragraph, subparagraph | The designation of the reference document referenced | The number of the paragraph, subparagraph |
| GOST 1467−93 | 3.2 | GOST 9336−75 | 2.2 |
| GOST 3118−77 | 2.2 | GOST 10929−76 | 2.2 |
| GOST 3640−94 | 2.2, 3.2 | GOST 11125−84 | 3.2 |
| GOST 3760−79 | 2.2 | GOST 11293−89 | 2.2 |
| GOST 3773−72 | 2.2 | GOST 12072.0−79 | 1.1, 3.3.1 |
| GOST 4204−77 | 2.2 | GOST 22860−93 | 3.2 |
| GOST 4461−77 | 2.2 | GOST 27067−86 | 2.2 |
| GOST 4658−73 | 2.2 | THAT 6−09−3704−74 | 2.2 |
| GOST 6552−80 | 2.2 | THAT 6−09−5313−87 | 2.2 |
| GOST 9293−74 | 2.2 |
