GOST 3240.20-76
GOST 3240.20−76 magnesium Alloys. Methods for determination of iron (with Change No. 1)
GOST 3240.20−76
Group B59
INTERSTATE STANDARD
MAGNESIUM ALLOYS
Methods of iron determination
Magnesium alloys.
Methods for determination of iron
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. REPLACE GOST 3240.27−76 in part in sect. VII
4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
The number of the paragraph, subparagraph |
| GOST 8.315−97 |
2.5 |
| GOST 804−93 |
3.2 |
| GOST 3118−77 |
2.2, 3.2 |
| GOST 3240.0−76 |
1.1 |
| GOST 3760−79 |
2.2 |
| GOST 4461−77 |
2.2, 3.2 |
| GOST 5456−79 |
2.2 |
| GOST 5457−75 |
3.2 |
| GOST 25086−87 |
2.2 |
| THAT 6−09−5404−88 |
2.2 |
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 sets the photometric method for the determination of iron (at mass fraction of iron from 0.001 to 0.2%) and atomic absorption method for determination of iron (at mass fraction of iron from 0.01 to 0.2%).
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 3240.0.
2. THE PHOTOMETRIC METHOD FOR THE DETERMINATION IRON CONTENT
2.1. The essence of the method
The method is based on reduction of iron to ferrous with hydroxylamine. Ferrous ions form at pH 3.5 to 4.5 with ortofenantrolinom compound, colored red. The intensity of the color measured at 
2.2. Apparatus, reagents and solutions
Spectrophotometer or photocolorimeter.
Hydrochloric acid according to GOST 3118, diluted 1:1.
Nitric acid according to GOST 4461.
Anhydrous sodium preservatory on the other 6−09−5404.
Hydroxylamine hydrochloric acid according to GOST 5456, 10% freshly prepared solution.
Ammonia according to GOST 3760 and diluted 1:1, 1:5.
Orthophenanthroline, 0,25% solution.
Standard iron solution
Solution A, prepared as follows: 1 g of iron metal recovered was dissolved in 30 cmof hydrochloric acid diluted 1:1, filtered in 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 iron.
Solution B is prepared as follows: 10 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 0.01 mg of iron
.
2.3. Analysis
2.3.1. When the mass fraction of iron to 0.01%
The shavings before taking the sample atminciai. A sample of alloy weighing 0.5 g was dissolved with heating in 20−25 cmof hydrochloric acid diluted 1:1. In the presence of a black precipitate of elemental zirconium are added dropwise nitric acid and boil to complete dissolution of the precipitate. If the precipitate is not completely dissolved, it should be filtered on a medium density filter, collecting the filtrate in a volumetric flask with a capacity of 100 cm
.
The filter with precipitate was placed in a porcelain crucible, calcined at 500 °C, cool, add 3 g of sodium peacemaking and fused at 600 °C. the Melt is dissolved in water, add 5 cmof hydrochloric acid diluted 1:1, and added to the main filtrate. To the solution add 5 cm
of a solution of hydroxylamine hydrochloric acid, neutralized with ammonia, initially diluted 1:1 and then diluted 1:5, to lilac paper «Congo», add 20 cm
orthophenanthroline solution, dilute to the mark with water and mix.
If the alloy contains zinc, then add 35−40 cmorthophenanthroline.
After 1 hour, measure the optical density of colored solution at 
(Changed edition, Rev. N 1)
.
2.3.2. When the mass fraction of iron in excess of 0.01%
The alloy solution is transferred into a measuring flask with a capacity of 100 cm, is diluted to the mark with water and mix. Pipetted 10 cm
of solution in a volumetric flask with a capacity of 100 cm
, add 5 cm
of hydrochloric acid hydroxylamine, neutralized as indicated above, add 20 cm
orthophenanthroline solution, dilute to the mark with water and mix.
Optical density of the solution measured as described in section 3.1. Mass fraction of iron found by the calibration schedule.
2.3.3. Construction of calibration curve
Eight volumetric flasks with a capacity of 100 cmmaking 0; 0,5; 1,0; 2,0; 4,0; 6,0; 8,0; 10,0 cm
of solution B, which corresponds to 0; 0,005; 0,01; 0,02; 0,04; 0,06; 0,08 and 0.1 mg of iron. To each flask add 2 cm
of hydrochloric acid diluted 1:1, 5 cm
of a solution of hydrochloric acid hydroxylamine, 25 cm
of water, then neutralized with ammonia, diluted 1:5, to lilac paper «Congo», add 20 cm
orthophenanthroline, dilute to the mark with water, mix and after 1 hour, measure the optical density of colored solutions.
As a solution comparison using the solution that does not contain a standard solution of iron.
On the found values of optical densities and their corresponding iron concentrations to build calibration curve.
(Changed edition, Rev. N 1).
2.4. Processing of the results
2.4.1. Mass fraction of iron () in percent is calculated by the formula
where — the amount of iron was found in the calibration schedule g;
— the weight of the portion of the alloy taken for photometry,
2.4.2. Allowable absolute differences of the results of the parallel definitions should not exceed the values given in table.1.
Table 1
| Mass fraction of iron, % |
The absolute allowable difference, % |
| From 0.001 to 0.005 |
0,0005 |
| SV. A 0.005 «0.010 is |
0,001 |
| «0,010» 0,030 |
0,003 |
| «0,03» 0,08 |
0,005 |
| «Of 0.08» to 0.20 |
0,01 |
2.4.1;
2.5. Control of measurement accuracy
Control of accuracy of measurement of mass fraction of iron from 0.01 to 0.2% is carried out using the State standard sample GSO 3363.
In addition, use the national 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 iron, using addition method.
(Added, Rev. N 1).
3. ATOMIC ABSORPTION METHOD FOR THE DETERMINATION IRON CONTENT
3.1. The essence of the method
The method is based on measuring the atomic absorption at the resonance line of iron 249,3 nm in the flames of mixtures of acetylene with air. Height fotometricheskogo plot of flame 2 see Framework components and impurities in the magnesium alloys definition of iron do not interfere. However, to identify the conditions of sputtering analyzed and calibration solutions in the past introduced based alloy (mg) and hydrochloric acid in appropriate concentrations.
3.2. Apparatus, reagents and solutions
Spectrophotometer atomic absorption.
Hydrochloric acid according to GOST 3118 and diluted 1:1.
Nitric acid according to GOST 4461, diluted 1:1.
Iron metal has been restored.
Standard solution of iron
1 g of iron is placed in a conical flask with a capacity of 250−300 cmand dissolved in 50 cm
of hydrochloric acid. 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 0.001 g of iron.
Primary magnesium ingots brand Mg95 according to GOST 804 in the form of chips.
A solution of magnesium 50 g/DM: 50 g of magnesium was dissolved in 800 cm
of a hydrochloric acid solution, transferred to a volumetric flask with a capacity of 1 DM
, made up to the mark with water, mix.
Acetylene in cylinders GOST 5457.
(Changed edition, Rev. N 1)
.
3.3. Analysis
3.3.1. The shavings before taking the sample atminciai. A sample of alloy weighing 1 g is placed in a conical flask with a capacity of 300−400 cmand dissolved in 30 cm
of hydrochloric acid. For the dissolution of copper-oxidized solution with a few drops of nitric acid and transferred to volumetric flask with a capacity of 100 cm
. The vessel, which conducted the dilution, rinsed with two portions of distilled water of 20 cm
and attach washings to the main solution. The mixture was diluted to the mark with water and mix thoroughly.
Solutions injected into the capillary of the spectrophotometer and measure the optical density of the flame. In order to avoid errors in unstable operation of the device after every four samples to check the slope of the calibration curve re-photoretrieval one of the previously analyzed solutions. When you change the optical density by more than 2% the analysis of the last four samples is repeated.
Are parallel to the analysis of control samples.
3.3.2. Construction of calibration curve
In seven volumetric flasks with a capacity of 100 cmis administered at 20 cm
of a solution of magnesium, from microburette add 0; 0,1; 0,25; 0,5; 1,0; 2,0 cm
standard solution of iron, which corresponds to 0; 0,1; 0,25; 0,5; 1,0 and 2,0 mg of iron, dilute to the mark with water, stirred, the solution is sprayed into the flame of acetylene-air and measure the magnitude of the absorption of iron. The measurement build the calibration graph.
(Changed edition, Rev. N 1).
3.4. Processing of the results
3.4.1. Mass fraction of iron () in percent is calculated by the formula
where is the mass of iron was found in the calibration schedule g;
— the weight of the portion of alloy,
(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.2.
Table 2
| Mass fraction of iron, % |
The absolute allowable difference, % |
| From 0.01 to 0.02 |
0,001 |
| SV. 0,02 «0,05 |
0,002 |
| «0,05» 0,10 |
0,003 |
| «To 0.10» to 0.20 |
0,004 |
3.5. Control of measurement accuracy
Accuracy control measurement is carried out according to claim 2.5.
(Added, Rev. N 1).
