GOST 851.1-93

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  ГОСТ 851.1-93

GOST 851.1−93 Magnesium primary. Methods of iron determination

GOST 851.1−93
Group B59

INTERSTATE STANDARD

MAGNESIUM PRIMARY

Methods of iron determination

Primary magnesium.
Methods for determination of iron

ISS 77.120.20
AXTU 1709

Date of introduction 1997−01−01

Preface

1 DEVELOPED by the Ukrainian scientific-research and design Institute of titanium

INTRODUCED by Gosstandart of Ukraine

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 3 dated February 17, 1993)

The adoption voted:

The name of the state	The name of the national authority standardization
The Republic Of Armenia	Armastajad
The Republic Of Belarus	Belstandart
The Republic Of Kazakhstan	Gosstandart Of The Republic Of Kazakhstan
The Republic Of Moldova	Moldovastandart
Russian Federation	Gosstandart Of Russia
Turkmenistan	Turkmengeologiya
The Republic Of Uzbekistan	Standards
Ukraine	Gosstandart Of Ukraine

3 Decree of the Russian Federation Committee on standardization, Metrology and certification from February, 20th, 1996 N 72 inter-state standard GOST 851.1−93 introduced directly as state standard of the Russian Federation from January 1, 1997

4 REPLACE GOST 851.1−87

5 REISSUE

INFORMATION DATA

REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

The designation of the reference document, to which this links	The number of the paragraph, subparagraph
GOST 8.315−97	2.2; 3.2; 4.2
GOST 61−75	2.2
GOST 199−78	2.2
GOST 3118−77	2.2
GOST 5456−79	2.2
GOST 5457−75	4.2
GOST 10157−79	3.2
GOST 11125−84	3.2; 4.2
GOST 14261−77	2.2; 3.2; 4.2
GOST 24231−80	1.2
GOST 25086−87	1.1; 1.5; 2.3.3; 2.4.3; 3.4.3: 4.3.2; 4.4.3
THAT 6−09−2227−85	2.2; 3.2; 4.2
THAT 6−09−3673−85	2.2

This standard specifies the photometric (with a mass fraction of iron from 0.002 to 0,060%) and atomic absorption (at a mass fraction of iron from 0.0005 to 0,060%) methods for determination of iron in primary magnesium.

If there are differences in the analysis carried out by the photometric method.

1 General requirements

1.1 General requirements for methods of analysis GOST 25086.

1.2 Sample pre-ofmagnesium according to GOST 24231.

1.3 Mass fraction of iron determined from two parallel batches.

1.4 When constructing a calibration chart, each point building on the average result of the three definitions of optical density or atomic absorption.

1.5 Permissible differences in results of analysis of the same samples obtained by the two methods, calculated according to GOST 25086.

1.6 When making the results of the analysis make reference to this standard, specify the method of determining and method of controlling the accuracy of the analysis.

2 the Photometric method for determination of iron

2.1 the essence of the method

The method is based on the formation in weak acidic medium is colored orange-red complex compound of bivalent iron with o-phenanthroline or 2,2'-dipyridil and subsequent measurement of optical density of the solution.

2.2 the Instrument, reagents and solutions

The spectrophotometer or photoelectric colorimeter.

Hydrochloric acid — according to GOST 3118, diluted 1:1, and the solution with molar concentration of 0.1 mol/DM.

Hydrochloric acid — according to GOST 14261.

Hydroxylamine hydrochloric acid — according to GOST 5456, solution with a mass concentration of 200 g/DM.

on-fenantrolin production of Czechoslovakia, a solution with a mass concentration of 2.5 g/DM.

2,2'-dipyridyl on the other 6−09−3673, a solution with a mass concentration of 5 g/DM: 0.5 g 2,2'-dipyridyl dissolved in 100 cmof water with the addition of 0.5 cmof a hydrochloric acid solution with molar concentration of 0.1 mol/DM.

Sodium acetate 3-water — GOST 199.

Acetic acid — according to GOST 61.

Buffer solution with pH 5: 272 g sodium acetate and dissolve in 500 cmof water, filter, add 240 cmof acetic acid, add water to 1000 cmand mixed.

Iron metal restored — on the other 6−09−2227.

State standard samples made in accordance with GOST 8.315.

Standard iron solution:

Solution a: 0,100 g of iron when heated, dissolved in 30 cmof hydrochloric acid according to GOST 14261. The solution was cooled to room temperature, poured into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix; fit for use for 6 months.

1 cmof solution A contains 0.1 mg of iron.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix; prepare before use.

1 cmof solution B contains 0.01

mg of iron.

2.3 analysis

2.3.1 Sample weighing 1.0 g was placed in a beaker with a capacity of 100−150 cm, add 10 cmof water, and small portions of 20 cmof a hydrochloric acid solution (1:1) was dissolved initially at room temperature and then by heating on a hot plate.

The solution was cooled to room temperature, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Aliquot part of the solution was 50 cm(at a mass fraction of iron up to 0.03%) or 25 cm(with mass fraction of iron in excess of 0.03%) is poured into a measuring flask with a capacity of 100 cm, add 2 cmof a solution of hydroxylamine hydrochloride, 15 cmbuffer solution, 5 cmof a solution of o-phenanthroline or 5 cmof a solution of 2,2'-dipyridyl, made up to the mark with water and mix. After 30 min, measure the optical density of the solution at a wavelength of 510 nm on the spectrophotometer or from 490 to 540 nm in photoelectric colorimeter. Solution comparison is the solution of the control about

trying.

2.3.2 For preparation of solution of control experience of 20 cmof a hydrochloric acid solution (1:1) was evaporated in a beaker with a capacity of 100−150 cmvolume cm 3, cooled to room temperature, poured into a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix. Then do as described in 2.3.1.

2.3.3 Construction of calibration graphs

To construct the calibration curve in mass fraction of iron from 0.002 to 0.01% in six of the seven volumetric flasks with a capacity of 100 cmplaced 1,0; 1,5; 2,0; 3,0; 4,0; 5,0 cmstandard solution B, which corresponds to 0,010; 0,015; 0,020; 0,030; 0,040; 0,050 mg of iron.

A seventh solution of the flask is a solution of the reference experiment.

To construct the calibration curve for the mass concentration of iron from 0.01 to 0.06% in six of the seven volumetric flasks with a capacity of 100 cmpour 0,5; 1,0; 1,5; 2,0; 2,5; 3,0 cmstandard solution A, which corresponds to 0,05; 0,10; 0,15; 0,20; 0,25; 0,30 mg of iron. A seventh solution of the flask is a solution of the reference experiment.

The solutions in all flasks was diluted to about 50 cmwith water, add 2 cmof a solution of hydroxylamine hydrochloric acid and then act as described in 2.3.1.

Solution comparison is the solution of the reference experiment.

According to the obtained results of the optical density of the calibration graphs built in accordance with GOST 25086.

2.4 Processing of results of analysis

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

, (1)

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

 — total volume of sample solution, cm;

 — the mass of sample, g;

 — volume aliquote parts of a solution of the sample, cm.

2.4.2 Standards of accuracy of analysis results

The values of the characteristics of error definitions: permitted discrepancies in the results of parallel measurements (the rate of convergence) and the results of the analysis for the same samples, obtained in two laboratories or in the same, but in different conditions (a measure of reproducibility), and the margins of error definitions ( — accuracy rate) at a confidence level =0.95 is shown in table 1.

Table 1

Mass fraction of iron, %	Characteristics error definitions %
From 0.002 to 0.005 incl.	0,0010	0,0015	0,0010
SV. 0,005 «0,010 «	0,0020	0,0030	0,0025
«0,010» 0,040 «	0,0030	0,0045	0,0035
«0,040» 0,060 «	0,0040	0,0060	0,0050

2.4.3 Control of accuracy of analysis results

Control of accuracy of analysis results is carried out according to state standard sample in accordance with GOST 25086.

Allowed to monitor the accuracy of analysis results by the method of additives in accordance with GOST 25086.

Additives is a standard solution A.

3 Atomic absorption method for determination of iron at a mass fraction of from 0.0005 to 0.0025%

3.1 the essence of the method

The method is based on measuring atomic absorption of iron at a wavelength of 248.3 nm in the electrothermal atomization mode.

The determination is carried out by standard addition.

3.2 Equipment, reagents and solutions

Spectrophotometer atomic absorption equipped with graphite atomizer, a source of excitation of spectral lines of iron.

Microspec with a capacity of 2 µm.

Argon — GOST 10157.

Hydrochloric acid — according to GOST 14261, diluted 1:1 and 1:99.

Nitric acid — according to GOST 11125.

Iron metal restored — on the other 6−09−2227.

State standard samples made in accordance with GOST 8.315.

Water bidistilled.

Standard iron solution:

Solution a: prepared according to 2.2.

Solution B: 5 cmsolution And placed in a volumetric flask with a capacity of 100 cm, is poured a solution of hydrochloric acid (1:99) to the mark and mix; prepare before use.

1 cmof solution B contains 5 µg of iron.

3.3 analysis

3.3.1 Sample weighing 0.5 g was placed in six beakers with a capacity of 300 cm, is added to 10 cmwater, 10 cmof hydrochloric acid (1:1) and lead dissolution, initially at room temperature and then under heating on an electric stove.

After complete dissolution of batches in each glass add 3−4 drops of nitric acid and boil for 1−2 min. the Solutions were cooled to room temperature and poured into volumetric flasks with a capacity of 50 cm.

In five out of six volumetric flasks with a solution of the sample add 0,5; 1,0; 1,5; 2,0; 2,5 cmstandard solution B, which corresponds to the mass concentration of the added iron 0,05; 0,10; 0,15; 0,20; 0,25 µg/cm.

The solutions in all flasks is poured to the mark with water and mix.

To prepare the solution in the reference experiment in a beaker with a capacity of 300 cmpour 10 cmof water, 10 cmof hydrochloric acid (1:1); heated to boiling, add 3−4 drops of nitric acid and boil for 1−2 min. the solution was Then cooled to room temperature, transferred to a volumetric flask with a capacity of 50 cm, made up to the mark with water and mix.

Consistently in a graphite cuvette with microspace enter solution: in the reference experiment, the sample, and in order of increasing iron concentration — solutions with additions of a standard solution of iron. Measurement of atomic absorption of iron is produced in the mode;

type of atomization is electro;

the lamp current, mA 10;

wavelength, nm — of 248.3;

the slot width of the device, nm — 0,2;

the drying temperature of the first stage, 353−393;

Stage II, 393−473;

the drying time stage I, 5;

II stage — 5;

the temperature of the ashing stage I, 473−873;

Stage II, 873−1473;

time ashing stage I, 5;

II stage — 5;

the temperature of the atomization, K — 2773;

the time of atomization, with — 5;

cleaning temperature, K — 2773;

cleaning — 2;

the speed of the argon cm/min — 200.

At the stage of atomization, the argon flow is stopped.

From the values of atomic absorption solutions containing additives of a standard solution of iron, deduct the value of atomic absorption of the sample solution. According to the obtained values of the difference between of atomic absorption and corresponding mass concentrations of added iron in µg/cmbuild a calibration curve, which find a massive concentration of iron in solution in the reference experiment and

sample.

3.3.2 In the case when the instrument is in aromatizirovannaya mode and performs its graduations, hinge samples weighing 0.5 g was poured into four glasses with a capacity of 300 cm, is poured 10 cmof water, 10 cmof hydrochloric acid (1:1) and further conducting the dissolution as described in 3.3.1. The solutions were transferred to volumetric flasks with a capacity of 50 cm.

In three of the four volumetric flasks with a solution of the sample add 0,5; 1,5; 2,5 cmstandard solution B, which corresponds to the mass concentration of the added iron 0,05; 0,15; 0,25 µg/cm.

The solutions in all flasks is poured to the mark with water and mix.

The solution in the reference experiment prepared as described in 3.3.1.

Microspace introduced into a graphite cuvette and the sample solution, and then in ascending concentrations of iron solutions containing additives of a standard solution of iron, and carry out the calibration of an instrument.

Measurement of atomic absorption of iron is carried out in mode on 3.3.1.

Then injected into the graphite cuvette, the solutions in the reference experiment and the sample, then conduct a measurement of the atomic absorption mode on 3.3.1.

After every 4−5 measurements of atomic absorption is carried out the purification of the graphite cuvette: microspace introduce water into it and produce the atomization process mode on 3.3.1.

3.4 Processing of analysis results

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

, (2)

where  — mass concentration of iron in the sample solution, µg/cm;

 — mass concentration of iron in solution in the reference experiment, µ g/cm;

 — the volume of the sample solution, cm;

 — weight of charge, g

.

3.4.2 Standards of accuracy of analysis results

The values of the characteristics of error definitions: permitted discrepancies in the results of parallel measurements (the rate of convergence) and the results of the analysis for the same samples, obtained in two laboratories or in the same, but in different conditions (a measure of reproducibility), and the margins of error definitions ( — accuracy rate) at a confidence level =0.95 is shown in table 2.

Table 2

Mass fraction of iron, %	Characteristics error definitions %
Between 0.0005 and 0.0015 incl.	0,0002	0,0003	0,0002
SV. 0,0015 «0,0025 «	0,0005	0,0008	About 0.0006

3.4.3 Control of accuracy of analysis results

Control of accuracy of analysis results is carried out according to state standard sample in accordance with GOST 25086.

4 Atomic absorption method for determination of iron at a mass fraction of from 0.002 to 0,060%

4.1 the essence of the method

The method is based on measuring atomic absorption of iron in the flame of acetylene-air at a wavelength of 248.3 nm.

4.2 Equipment, reagents and solutions

Spectrophotometer of atomic absorption with the excitation source spectral line of iron.

Acetylene — GOST 5457.

Nitric acid — according to GOST 11125.

Hydrochloric acid — according to GOST 14261, diluted 1:1 and 1:99.

Iron metal restored — on the other 6−09−2227.

State standard samples made in accordance with GOST 8.315.

Standard iron solution:

Solution a: prepared according to 2.2.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, is poured a solution of hydrochloric acid (1:99) to the mark and mix; prepare before use.

1 cmof a solution contains 0.01 mg of iron.

4.3 analysis

4.3.1 Sample mass of 0.5 g was placed in a beaker with a capacity of 200 cm, is poured 10 cmof water, 10 cmof hydrochloric acid (1:1) and then produce a dissolution as specified in 3.3.1. The solution was poured into a volumetric flask with a capacity of 50 cm.

The solution in the reference experiment prepared as described in 3.3.1.

The solutions in the reference experiment and the sample is sprayed into the flame of acetylene-air and measure the atomic absorption at a wavelength of 248.3 nm.

Before measuring the atomic absorption of the sample solutions and the reference experiment is carried out construction of calibration curve or the calibration of an instrument if the instrument is operated in automated mode.

4.3.2 Construction of calibration graphs

When the mass fraction of iron from 0.002 to 0,010% in five out of six volumetric flasks with a capacity of 50 cmis placed 1,0; 2,0; 3,0; 4,0; 5,0 cmstandard solution B, which corresponds to the mass concentration of iron is 0,2; 0,4; 0,6; 0,8; 1,0 µg/cm. The sixth solution of the flask is a solution of the reference experiment.

When the mass fraction of iron from 0.01 to 0.06% in six of the seven volumetric flasks with a capacity of 50 cmplaced 0,5; 1,0; 1,5; 2,0; 2,5; 3,0 cmstandard solution A, which corresponds to the mass concentration of iron 1,0; 2,0; 3,0; 4,0; 5,0; 6,0 µg/cm. A seventh solution of the flask is a solution of the reference experiment.

The solutions in all flasks is poured a solution of hydrochloric acid (1:99) to the mark, stirred, is sprayed into the flame of acetylene-air and measure the atomic absorption at a wavelength of 248.3 nm.

The results of atomic absorption and corresponding mass concentrations of iron in g/cmbuild calibration charts in accordance with GOST 25086

.

4.3.3 calibration of the spectrophotometer

When the mass fraction of iron from 0.002 to 0,010% in three of the four volumetric flasks with a capacity of 50 cmis placed 1,0; 3,0; 5,0 cmstandard solution B, which corresponds to the mass concentration of iron is 0,2; 0,6; 1,0 µg/cm. The solution to the fourth flask is a solution of the reference experiment.

When the mass fraction of iron from 0.01 to 0.06% in three of the four volumetric flasks with a capacity of 50 cmpour 0,5; 1,5; 3,0 cmstandard solution A, which corresponds to the mass concentration of iron 1,0; 3,0; 6,0 mg/cm. The solution to the fourth flask is a solution of the reference experiment.

The solutions in all flasks is poured a solution of hydrochloric acid (1:99) to the mark, mixed and sprayed in the flame acetylene-air, in sequence: a solution of the reference experiment and the standard solutions in ascending concentrations of iron and carry out the calibration of an instrument.

Measurement of atomic absorption is carried out at a wavelength of 248.3 nm.

4.4 Processing of analysis results

4.4.1 Mass fraction of iron () in percent is calculated by the formula

, (3)

where  — mass concentration of iron in the sample solution, µg/cm;

 — mass concentration of iron in solution in the reference experiment, µ g/cm;

 — the volume of the sample solution, cm;

 — weight of charge, g

.

4.4.2 Standards of accuracy of analysis results

The values of the characteristics of error definitions: permitted discrepancies in the results of parallel measurements (the rate of convergence) and the results of the analysis of the same samples obtained in two laboratories or in the same, but in different conditions (a measure of reproducibility), and the margins of error definitions ( — accuracy rate) at a confidence level =0.95 is shown in table 3.

Table 3

Mass fraction of iron, %	Characteristics error definitions %
From 0.002 to 0.005 incl.	0,0007	0,0010	0,0008
SV. 0,005 «0,010 «	0,0015	0,0020	0.0016 inch
«0,010» 0,030 «	0,0030	0,0045	0,0035
«0,030» to 0,060 «	0,0050	0,0070	0,0060

4.4.3 Control of accuracy of analysis results

Control of accuracy of analysis results is carried out according to state standard sample in accordance with GOST 25086.

Allowed to monitor the accuracy of analysis results by the method of additives in accordance with GOST 25086.

Additives are standard solutions A or B.