GOST 3240.6-76
GOST 3240.6−76 magnesium Alloys. Methods for determination of cadmium (Change No. 1)
GOST 3240.6−76
Group B59
INTERSTATE STANDARD
MAGNESIUM ALLOYS
Methods for determination of cadmium
Magnesium alloys.
Methods for determination of cadmium
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
3. INTRODUCED FOR THE FIRST TIME
4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
Item number |
| GOST 8.315−97 |
2.5 |
| GOST 195−77 |
2.2 |
| GOST 804−93 |
2.2, 3.2 |
| GOST 1467−93 |
2.2, 3.2 |
| GOST 3118−77 |
2.2, 3.2 |
| GOST 3240.0−76 |
1.1 |
| GOST 3760−79 |
2.2 |
| GOST 3773−72 |
2.2 |
| GOST 4461−77 |
3.2 |
| GOST 5457−75 |
3.2 |
| GOST 25086−87 |
2.5 |
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 cadmium (at a mass fraction of cadmium from 0.02 to 2%).
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 3240.0.
2. POLAROGRAPHIC METHOD FOR THE DETERMINATION OF CADMIUM
2.1. The method is based on the recovery of cadmium on dripping mercuric electrode in ammonia background electrolyte in the region of potentials from minus 0.6 to minus 0,8 Century
2.2. Apparatus, reagents and solutions
Oscillographic polarograph the type of OP-2 or a device of another type.
Ammonia water according to GOST 3760.
Ammonium chloride according to GOST 3773.
Hydrochloric acid according to GOST 3118.
Sodium sanitarily according to GOST 195.
Electrolyte background; prepared as follows: 500 cmof hot water dissolve sequentially 100 cm
of ammonia, 50 g of anhydrous salt semitecolo sodium and 100 g of ammonium chloride, stirred and filtered in a volumetric flask with a capacity of 1 DM
, then cooled. Then to the filtrate is added 170 cm
ammonia and adjusted to the mark with water.
Cadmium GOST 1467.
Primary magnesium ingots according to GOST 804 in the form of chips.
A standard solution of cadmium; prepared as follows: 1 g of cadmium of 99.9% purity is dissolved in 20 cmof hydrochloric acid, transferred into 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 cadmium
.
2.1; 2.2. (Changed edition, Rev. N 1).
2.3. Analysis
2.3.1. A portion of the alloy depending on the mass fraction of cadmium (table.1) dissolved in 20 cmof hydrochloric acid and transferred to volumetric flask with a capacity of 250 cm
. The solution was topped up to the mark and the background electrolyte, mixed and polarographic at a potential of minus 0.6 to minus 0,8 Century
Table 1
| Mass fraction of cadmium, % |
The mass of charge, g |
| From 0.02 to 0.1 |
1,0 |
| SV. 0,1 «1 |
0,5 |
| «1» 2 |
0,25 |
Mass fraction of cadmium found at additives or calibration schedule.
(Changed edition, Rev. N 1).
2.3.2. Construction of calibration curve
Six glasses are placed 1 g of pure magnesium, dissolved in 20 cmof hydrochloric acid, add 1−2 cm
of the solution naternicola ammonium is evaporated to obtain a moist salt, dissolve the salt in 10 cm
of hydrochloric acid and transferred the solution in the volumetric flask with a capacity of 100 cm
. Poured from the burette 0; 0,2; 0,6; 0,8; 1,0; 2,0 3.0 cm and
a standard solution of cadmium. The solution was diluted to the mark with background electrolyte, mixed and polarographic.
2.4. Processing of the results
2.4.1. Mass fraction of cadmium (a) 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 cadmium, mm;
— weight of cadmium, corresponding to the standard additive, g;
— the weight of the portion of alloy,
(Changed edition, Rev. N 1).
2.4.1 a. Mass fraction of cadmium (a) in percent for the calibration schedule is calculated by the formula
where the wave height of test solution, mm;
— the total volume of solution, cm
;
— the ratio of the height of the standard solution in mm concentration of cadmium 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
| Mass fraction of cadmium, % |
The absolute allowable difference, % |
| From 0.02 to 0.05 |
0,002 |
| SV. 0,05 «0,10 |
0,005 |
| «0,10» 0,3 |
0,01 |
| «Of 0.3» to 0.8 |
0,04 |
| «To 0.8» to 2.0 |
0,10 |
2.5 accuracy Control measurements
To control the accuracy of measuring the mass fraction of cadmium from 0.02 to 2% using the state standard samples of magnesium alloys, and industry 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 cadmium by the method of additions.
(Added, Rev. N 1).
3. ATOMIC ABSORPTION METHOD FOR DETERMINATION OF CADMIUM
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 of cadmium at a wavelength of 228,8 nm in the flame acetylene-air. Height fotometricheskogo plot flame 1 see Components of magnesium alloys, and impurities on the results of determinations are not affected, however, to identify the conditions of sputtering and analyze the calibration solutions should approximate the adjustment of the content of acids and bases alloy.
3.2. Apparatus, reagents and solutions
Atomic absorption spectrophotometer.
Hydrochloric acid according to GOST 3118, diluted 1:1.
Nitric acid according to GOST 4461, diluted 1:1.
Magnesium chloride, solution; is prepared as follows: 50 g of magnesium brand Мг96 according to GOST 804 is dissolved in 800 cmof hydrochloric acid, transferred to a volumetric flask with a capacity of 1 DM
, diluted with distilled water to the mark and mix.
1 cmof the solution contains 0.05 g of magnesium.
Standard solutions of cadmium chloride.
Solution A, prepared as follows: 1 g of cadmium of high purity according to GOST 1467растворяют by heating in 25 cmof nitric acid, add 50 cm
of hydrochloric acid, transferred into a volumetric flask with a capacity of 1 DM
and dilute to the mark with water.
1 cmof the solution contains 1 mg of cadmium.
Solution B is prepared as follows: 100 cmof solution A is taken in a volumetric flask with a capacity of 1 DM
, dilute to the mark with water and mix.
1 cmof a solution contains 0.1 mg of cadmium.
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 with a capacity of 300 cm, is dissolved in 30 cm
of a hydrochloric acid solution, add 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
, made up to the mark with water, mix and carry out dilution in accordance with the table.3.
Table 3
| Mass fraction of cadmium, % |
Dilution is the solution, cm |
| From 0.02 to 0.15 |
The entire solution |
| SV. 0,15 «1,0 |
10/100 |
| «1,0» 2,0 |
5/100 |
Parallel to the sample conduct analysis of control experience.
Measure the atomic absorption of cadmium in the sample solution, the solution control experience and solutions to build the calibration curve in atomic absorption spectrophotometer relative to distilled water at a wavelength of 228,8 nm in the flame acetylene-air.
The concentration of cadmium 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 cadmium ranging from 0.02 to 0.15% in a series of volumetric flasks with a capacity of 100 cmis administered at 20 cm
of a solution of magnesium and 0; 1,0; 2,0; 4,0; 6,0; 8,0; 10,0; 12,0 and 15.0 cm
of a solution that fits 0; 0,10; 0,20; 0,40; 0,60; 0,80; 1,00; 1,20 and 1.50 mg of cadmium.
When the mass fraction of cadmium from 0.15 to 1.00% in a series of volumetric flasks with a capacity of 100 cmis administered at 2 cm
of a solution of magnesium, 0; 0,15; 0,20; 0,40; 0,80 and 1,00 mg of cadmium, which corresponds to the amount of solution B 0; 1,5; 2,0; 4,0; 6,0; 8,0 and 10.0 cm
.
When the mass fraction of cadmium from 1.0 to 2.0% in a series of volumetric flasks with a capacity of 100 cminject 1 cm
of solution of magnesium, 0; 5,0; 6,0; 8,0 and 10,0 cm
of solution B, which corresponds to 0; 0,5; 0,6; 0,8 and 1,0 mg of cadmium.
Solutions for calibration topped up to the mark with water, mix and measure the atomic absorption of cadmium according to claim
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 atomic absorption and corresponding contents of cadmium build the calibration graph
IR.
3.4. Processing of the results
3.4.1. Mass fraction of cadmium (a) in percent is calculated by the formula
where is the mass of cadmium in the sample solution found by the calibration schedule g;
— mass of cadmium in solution in the reference experiment, was found in the calibration schedule g;
— the weight of the portion of sample taken for spectrophotometry,
3.4.2. Allowable absolute differences of the results of the parallel definitions should not exceed the values given in table.4.
Table 4
| Mass fraction of cadmium, % |
The absolute allowable difference, % |
| From 0.02 to 0.05 |
0,0015 |
| SV. Of 0.05 «to 0.15 |
0,005 |
| «To 0.15» to 0.40 |
0,01 |
| «Of 0.4» to 1.0 |
0,02 |
| «1,0» 2,0 |
0,04 |
3.1
3.5. Control of measurement accuracy
Accuracy control measurement is carried out according to claim 2.5.
(Added, Rev. N 1).
