GOST 3240.3-76

• gost-32403-76.pdf (191.37 KiB)
  ГОСТ 3240.3-76

GOST 3240.3−76 magnesium Alloys. Methods for determination of zinc (with Change No. 1)

GOST 3240.3−76

Group B59

INTERSTATE STANDARD

MAGNESIUM ALLOYS

Methods for determination of zinc

Magnesium alloys.
Methods for determination of zinc

ISS 77.120.20
AXTU 1709

Date of introduction 1978−01−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of aviation industry of the USSR

2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 28.12.76 N 2889

3. REPLACE GOST 3240−56 in part of sec. IV

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Limitation of actions taken by Protocol No. 2−92 of the Interstate Council for standardization, Metrology and certification (ICS 2−93)

6. EDITION with Change No. 1, approved in June 1987 (IUS 11−87)


This standard specifies the polarographic and atomic absorption methods for the determination of zinc (at a mass fraction of zinc from 0.02 to 8%).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 3240.0.

2. POLAROGRAPHIC METHOD FOR THE DETERMINATION OF ZINC CONTENT

2.1. The essence of the method

The method is based on the recovery of zinc on dripping mercuric electrode in ammonium electrolyte background in the field of potentials from minus 1.0 to 1.4 V.

2.2. Apparatus, reagents and solutions

The OP polarograph type or other, providing the sensitivity.

Hydrochloric acid according to GOST 3118, diluted 1:1.

Ammonia according to GOST 3760.

Ammonium chloride according to GOST 3773.

Sodium sanitarily according to GOST 195, saturated solution.

Background electrolyte; prepared as follows: 1000 cmof solution take 100 g of ammonium chloride, 100 CCof ammonia, 50 g of sodium semitecolo.

Zinc GOST 3640 brand C0.

Standard solution of zinc, 1 g of zinc is dissolved in 30 cmof a hydrochloric acid solution, transferred to a volumetric flask with a capacity of 1 DM, dilute to the mark with water and mix.

1 cmof the solution contains 1 mg of zinc.

Primary magnesium ingots according to GOST 804 in the form of chips.

2.3. The weight of the portion of the alloy is determined depending on the mass fraction of zinc in the amounts indicated in the table.1. The sample is placed in a beaker with a capacity of 250 cm, and dissolved in 30 cmof hydrochloric acid and transferred to volumetric flask of capacity indicated in the table.1. To the solution was added 15 cmof ammonia and add to the label background electrolyte, mixed and polarographic at a potential of minus 1.0 to minus 1.4 V.

Table 1

2.1−2.3. (Changed edition, Rev. N 1).

2.3.1. Construction of calibration curve

The weight of magnesium metal take depending on the mass fraction of zinc in the amounts indicated in the table.1, five glasses with a capacity of 100 cm, is dissolved in 30 cmof a hydrochloric acid solution, adding successively to each a glass of 0; 0,5; 1,0; 5,0; 10,0 and 20,0 cmstandard solution of zinc, which corresponds to 0; 0,5; 1,0; 5,0; 10,0 and 20,0 mg of zinc. The solution was transferred to volumetric flask with a capacity of 100 cm, made up to the mark and the background electrolyte, mixed and removed a diffusion wave of zinc at a potential of minus 1.0 to minus 1.4 V.

(Added, Rev. N 1).

2.4. Processing of the results

2.4.1. Mass fraction of zinc () in percent is calculated by the formula

,

where the wave height of the investigated solution;

 — wave heights of the investigated solution with the addition of a standard solution of zinc, mm;

 — the amount of zinc corresponding to the standard additive, g;

 — the weight of the portion of alloy,

2.4.1. Mass fraction of zinc () on the calibration schedule in percent is calculated by the formula

,

where the wave height of test solution, mm;

 — the total volume of solution, cm;

 — the ratio of the wave height of a standard solution in mm concentration of lead in mg/DM;

 — the weight of the portion of alloy,

(Added, Rev. N 1).

2.4.2. Allowable absolute differences of the results of the parallel definitions should not exceed the values given in table.2.

Table 2

(Changed edition, Rev. N 1).

2.5. Control of measurement accuracy

Control the accuracy of measuring the mass fraction of zinc from 0.02 to 8.0% is carried out using the State standard sample GSO 3363.

In addition, there may be used the state standard samples of magnesium alloys, newly issued, as well as industry standard samples and standard samples of the enterprise of magnesium alloys, issued in accordance with GOST 8.315. Accuracy control measurement is carried out in accordance with GOST 25086.

Allowed to control the accuracy of measuring the mass fraction of zinc by the method of additions.

(Added, Rev. N 1).

3. ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF ZINC CONTENT

3.1. The essence of the method

The method is based on dissolving the samples in hydrochloric acid in the presence of nitric acid and subsequent measurement of the atomic absorption with zinc at a wavelength of 213,9 nm in the flame acetylene-air. Height fotometricheskogo phase 1, see Components and impurities contained in the magnesium alloys, the results of the analysis are not affected, however, to identify the conditions of sputtering analyzed and calibration solutions in the last equation of the content of the basics of samples, as well as acids.

3.2. Apparatus, reagents and solutions

Spectrophotometer atomic absorption.

Hydrochloric acid according to GOST 3118, distilled, diluted 1:1.

Magnesium GOST-804 brand Мг96.

A solution of magnesium 50 g/DM: 50 g of magnesium carefully dissolved in 800 cmof hydrochloric acid. The solution was cooled, transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof the solution contains 0.05 g of magnesium.

Zinc GOST 3640 brand C0.

Standard solutions of zinc

Solution A, prepared as follows: 0.5 g of zinc is dissolved in 50 cmof hydrochloric acid, transferred into a volumetric flask with a capacity of 500 cm, is diluted with bidistilled water to the mark and mix.

1 cmof the solution contains 0.001 g of zinc.

Solution B is prepared as follows: 100 cmof solution A is taken in a volumetric flask with a capacity of 1 DMand diluted with bidistilled water to the mark.

1 cmof the solution contains 0.0001 g of zinc.

Bidistilled water according to GOST 4517.

Acetylene in cylinders GOST 5

457.

3.3. Analysis

3.3.1. A portion of the sample weighing 1 g is placed in a beaker or conical flask with a capacity of 250−300 cm, dissolved in 30 cmof hydrochloric acid with addition of 5−10 drops of nitric acid and boil to remove oxides of nitrogen. The solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, top up to the mark with water, mix and carry out dilution in accordance with the table.3.

Table 3

Parallel to the sample conduct analysis of control experience.

Measure the atomic absorption of zinc in the sample solution, the solution control experience and solutions to build the calibration curve in atomic absorption spectrophotometer relative to double-distilled water at a wavelength of 213,9 nm in the flame acetylene-air.

Mass fraction of zinc in the sample solution and the reference experiment is determined by the calibration schedule.

3.3.2 Construction of calibration curve

To construct the calibration curve for the mass concentration of zinc ranging from 0.02 to 0.08% in a series of volumetric flasks with a capacity of 100 cmis administered at 20 cmof a solution of magnesium and 0; 1,0; 2,0; 4,0; 6,0; 8,0 and 10 cmof solution B, which corresponds to 0; 0,1; 0,2; 0,4; 0,6; 0,8 and 1.0 mg of zinc.

When the mass fraction of zinc from 0.08 to 0.7% in a series of volumetric flasks with a capacity of 100 cmis administered at 2 cmof a solution of magnesium, 0; 0,8; 2,0; 4,0; 6,0 and 8,0 cmof solution B, which corresponds to 0; 0,08; 0,20; 0,40; 0,60 and 0,80 mg of zinc.

When the mass fraction of zinc from 0.7 to 5.0% in a series of volumetric flasks with a capacity of 100 cmis administered at 0.2 cmof a solution of magnesium and 0; 0,6; 1,0; 2,0; 3,0; 4,0 and 5.0 cmof solution B, which corresponds to 0; 0,06; 0,10; 0,20; 0,30; 0,40 and 0.50 mg of zinc.

When the mass fraction of zinc from 5 to 10% in a series of volumetric flasks with a capacity of 250 cmis administered at 0.2 cmof a solution of magnesium, 0; 5,0; 7,5; 10,0; 12,5 cmof solution B, which corresponds to 0; 0,50; 0,75; 1,00; 1,25 mg of zinc.

Solutions for calibration topped up to the mark with water, mix and measure the atomic absorption of zinc according to claim 3.3.1.

From the obtained values of atomic absorption solutions containing a standard solution, subtract the value of atomic absorption of a solution containing a standard solution, and the obtained values of the atomic absorption of the solution and the respective contents of the zinc build calibration g

Rafik.

3.1−3.3.2. (Changed edition, Rev. N 1).

3.4. Processing of the results

3.4.1. Mass fraction of zinc () in percent is calculated by the formula

,

where is the mass of zinc in the sample solution found by the calibration schedule g;

 — the mass of zinc in solution in the reference experiment, was found in the calibration schedule g;

 — the weight of the portion of sample taken for spectrophotometry,

(Changed edition, Rev. N 1).

3.4.2. Allowable absolute differences of the results of the parallel definitions should not exceed the values given in table.4.

Table 4

3.5. Accuracy control measurement is carried out according to claim 2.5.

(Added, Rev. N 1).