GOST 12358-2002

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  ГОСТ 12358-2002

GOST 12358−2002 Steel alloyed and high alloy. Methods for determination of arsenic

GOST 12358−2002

Group B39

INTERSTATE STANDARD

STEEL ALLOYED AND HIGH-ALLOYED

Methods for determination of arsenic

Alloyed and highalloyed steels. Methods for determination of arsenic

ISS 77.080.20
AXTU 0709

Date of introduction 2003−05−01

Preface

1 DEVELOPED by the Interstate technical Committee for standardization MTK 145 «monitoring Methods of steel products"

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 21 dated may 30, 2002)

The adoption voted:

3 Resolution of the State Committee of the Russian Federation on standardization and Metrology from September, 11th, 2002 N 331-St inter-state standard GOST 12358−2002 introduced directly as state standard of the Russian Federation from 1 may 2003.

4 REPLACE GOST 12358−82

The re-release (as of April 2008)

1 Scope

This standard specifies the flameless atomic absorption (when the mass fraction of arsenic from 0.0002% to 0.01%), photometric (at a mass fraction of arsenic from 0.002% to 0.2%) and potentiometric (when the mass fraction of arsenic from 0,05% to 0,2%) methods for determination of arsenic in the alloy and high-alloy steels.

2 Normative references

The present standard features references to the following standards:

GOST 859−2001 Copper. Brand

GOST 1973−77 arsenious Anhydride. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3765−78 Ammonium molybdate. Specifications

GOST 4160−74 Potassium bromide. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4457−74 Potassium branovitsky. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 5456−79 of Hydroxylamine hydrochloride. Specifications

GOST 5817−77 tartaric Acid. Specifications

GOST 5841−74 Hydrazine sulfate

GOST 5962−67* ethyl Alcohol rectified. Specifications

________________

* On the territory of the Russian Federation GOST R 51652−2000.


GOST 6552−80 orthophosphoric Acid. Specifications

GOST 9949−76 Xylene of coal-tar. Specifications

GOST 10157−79 Argon gaseous and liquid. Specifications

GOST 11125−84 nitric Acid of high purity. Specifications

GOST 14204−69 Device for separation of arsenic in steels, cast irons and alloys. Specifications

GOST 14261−77 hydrochloric Acid of high purity. Specifications

GOST 14262−78 sulphuric Acid of high purity. Specifications

GOST 18300−87 ethyl rectified technical. Specifications

GOST 19522−74 Ammonium radamisty technical. Specifications

GOST 24147−80 aqueous Ammonia of high purity. Specifications

GOST 28473−90 Iron, steel, ferroalloys, chromium and manganese metal. General requirements for methods of analysis

3 General requirements

General requirements for methods of analysis GOST 28473.

4 Flameless atomic absorption method for the determination of arsenic

4.1 the essence of the method

The method is based on the measurement values of the absorption of resonance radiation by free atoms of arsenic at a wavelength of 193.7 nm, formed with the introduction of the analyzed solution into the graphite oven.

Arsenic is pre-separated by distillation from the basic components of steel in the form of trichloride of arsenic from hydrochloric acid solution in the presence of sulfate hydrazine and potassium bromide or by precipitation with thioacetamide as a sulfide in 0.5 mol/DMsulfuric acid solution in the presence of the collector of sulphide of copper and tartaric acid as complexing agents.

4.2 Equipment, reagents, solutions

Atomic absorption spectrophotometer with all accessories, equipped with a graphite atomizer.

Lamp for determination of arsenic.

Micropipettes with a capacity of 20 and 50 micysmf.

Argon of high purity according to GOST 10157 and a mixture of argon with 5% hydrogen.

Apparatus for separation of arsenic GOST 14204 or any other type.

Hydrochloric acid according to GOST 3118 or GOST 14261 and diluted 1:1.

Nitric acid according to GOST 4461 or GOST 11125 and diluted 1:1.

Sulfuric acid according to GOST 4204 or GOST 14262, diluted 1:1 solution of 2.5 mol/DM.

Orthophosphoric acid according to GOST 6552 and diluted 1:1.

A mixture of hydrochloric and nitric acids (3:1): to 150 cmof hydrochloric acid add 50 cmof nitric acid and stirred; prepared immediately before use.

A mixture of hydrochloric and nitric acids, diluted (1:1): to 150 cmof hydrochloric acid add 50 cmof nitric acid, 200 cmof water and mix; prepare immediately before use.

Tartaric acid according to GOST 5817, a solution of 500 g/DM.

Ammonia water according to GOST 3760 or GOST 24147.

Hydroxylamine hydrochloride according to GOST 5456.

Ammonium radamisty according to GOST 19522, a solution of 50 g/DM.

Potassium bromide according to GOST 4160.

Sodium hydroxide according to GOST 4328, a solution of 50 g/cm.

Hydrazine sulfate according to GOST 5841.

Xylene according to GOST 9949.

The thioacetamide, recrystallized in xylene, a solution of 20 g/DM.

Recrystallization of thioacetamide: 30 g of thioacetamide dissolved in 100 cmof xylene at 85−90 °C with stirring. The upper layer of solution carefully decanted into a dry beaker with a capacity of 600−800 cm. In the glass with the remainder added to 100 cmof xylene, and dissolve again at 85−90 °C. the Upper layer of a solution of thioacetamide poured into the same beaker with a capacity of 600−800 cm. The operation is performed 4−5 times. The rest is thrown away. The resulting solution was cooled in running water. Precipitated crystals of the thioacetamide was filtered on a Buchner funnel with two filter «white ribbon». The crystals are washed 2−3 times with xylene, dried in air.

Copper grade М00бк according to the GOST 859.

Copper nitrate, solution 0,01 g/cm: 1 g of copper is dissolved by heating in 15−20 cmof nitric acid (1:1). The solution was boiled to remove oxides of nitrogen, cooled, diluted with water to 100 cmand mixed.

Iron metal, OS.CH., carbonyl.

Universal indicator paper pH 1−10.

Arsenious anhydride mark «refined» according to GOST 1973.

Sodium mistakemistake ortho (NaAsO·HO).

Standard solutions of arsenic.

Solution a: 0,132 g of arsenious anhydride is dissolved in 5 cmof sodium hydroxide solution, dilute with water to 200 cm, and was added sulfuric acid (1:1) until neutral reaction of universal indicator paper. The solution was transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

Preparation of a standard solution of sodium michalowskiego ortho: 0,2801 g michalowskiego sodium ortho dissolved in 200 cmof water is added sulfuric acid (1:1) until neutral reaction of universal indicator paper. The solution was transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmstandard solution contains 0.0001 g of arsenic.

Solution B: 10 cmstandard solution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

1 cmstandard solution B has the 0.00001 g of arsenic.

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

1 cmstandard solution contains 0,000001 g of arsenic.

4.3 analysis

4.3.1 Preparation of test solution

4.3.1.1 separation of the arsenic by distillation in the form of arsenic trichloride

Weigh a portion of the sample in accordance with table 1. Weighing results in grams is recorded with precision to the fourth decimal place. The sample is placed in a beaker (or flask) with a capacity of 250−300 cm, 30 cm, pour themixture of hydrochloric and nitric acids (3:1), 20 cmof sulphuric acid (1:1) and 10 cmof phosphoric acid (1:1).

Table 1

A glass (or flask) cover watch glass, and dissolve a portion with a moderate heat. Rinse watch glass with a little water and evaporate the solution prior to the allocation of sulphuric acid fumes. After cooling, cautiously add 30 cmof hydrochloric acid (1:1) and transfer the solution into a flask for the separation of arsenic. To the solution was added 0.5 g of potassium bromide, 0.5 g of hydrazine sulphate and slowly distilled arsenic trichloride in the apparatus for distillation at 110−120 °C in the mantle. The distillate is collected in a glass receiver with a capacity of 100 cm, containing 10 cmof water. Distillation continued until until the receiver will not pass the original volume. To the distillate add 10 cmof nitric acid.

4.3.1.2 Separation of arsenic by precipitation as a sulfide by thioacetamide

Weigh a portion of the sample in accordance with table 1. Weighing results in grams is recorded with precision to the fourth decimal place. The sample is placed in a beaker (or flask) with a capacity of 250−300 cm, 30 cm, pour themixture of hydrochloric and nitric acids (3:1), cover the beaker (or flask) watch glass and dissolve a portion with a moderate heat, cool, remove the watch glass by rinsing it with a little water. Pour 20 cmof sulphuric acid (1:1) and evaporated the solution to start the selection of sulfuric acid vapor, is cooled. Salt dissolved in 40−50 cmof water when heated, pour 10 cmof a solution of tartaric acid, the solution is heated for 5−10 minutes, cool, add ammonia to pH 8−9 by universal indicator solution and heated for 15−20 min at 90−95 °C until complete dissolution of the precipitate tungsten acid, cool. The solution was poured sulfuric acid (1:1) to pH 2 by universal indicator paper and 10 cmin excess, made up solution to 180 cmand heated to boiling. Carefully add 2−5 g of hydroxylamine hydrochloride, and boil the solution until complete reduction of iron (by the reaction with ammonium radamisty). Add 10 cmof a solution of thioacetamide, 1 cmof solution of nitrate of copper, kept the solution from precipitated sediment sulphides in 10−15 minutes on a warm spot plate, add another 10 cmof a solution of thioacetamide, allowed to stand at 85−90 °C for 30−40 min and cooled. Through 4−18 h, the precipitate filtered off sulphides on the two filters «white ribbon», washed 6−7 times with cold water. The filtrate is discarded. The filter cake is dissolved in 30−40 cm(chunks 10 cm) of a hot mixture of hydrochloric and nitric acids, diluted (1:1) and washed the filter with hot water 3−4 times, collecting the filtrate and washings into the beaker (or flask), which conducted the deposition. The filter is discarded.

4.3.2 Spectrometric measurement

The test solution prepared according to 4.3.1.1 or 4.3.1.2 and evaporated to dryness. Salt is dissolved by heating in 5 cmof nitric acid (1:1), covering the beaker (or flask) watch glass, and cooled. The solution was transferred to a volumetric flask with a capacity of 25 cm, top up to the mark with water and mix. Take a micropipette aliquot part of the solution, equal to 20−50 micysmf(table 1), injected into the graphite furnace and record the value of the absorption of resonance radiation by free atoms of arsenic at a wavelength of 193.7 nm. For measurements taken at least three alikvotnih parts of the solution. Oven burn at a maximum temperature within 5 s.

The mass of arsenic found at the calibration schedule subject to amendments the reference experiment.

4.3.3 preparation of the device for measuring

Activation of the device, setting the spectrophotometer at the resonant radiation, the adjustment of the control unit, the automation unit is carried out according to the instructions supplied with the device.

The conditions of determination of arsenic:

analytical line (s) — of 193.7 nm;

the spectral slit width of 0.7 nm;

time of drying at 145 °C — 15 s;

the decomposition at 900 °C — 12;

time atomization at 2250 °C — 5 s;

mode of inert gas, the minimum disconnecting under autorizatii.

4.3.4 Construction of calibration curve

In the beakers (or flasks) with a capacity of 250−300 cmis placed sample of carbonyl iron in the amount corresponding to the weight of the sample (table 1), and measured amount of standard solution of arsenic (table 2).

Table 2

All the glasses are poured acid as the dissolution of the sample, and further receives, as described in 4.3.1−4.3.3.

From the values of absorbance of analyzed solutions is subtracted the value of the optical density of the solution in the reference experiment. On the found values of optical density and corresponding mass of arsenic build the calibration graph.

5 Photometric method for the determination of arsenic

5.1 the essence of the method

The method is based on formation of blue arsenic-molybdenum complex in the interaction of pentavalent arsenic with ammonium molybdate in the presence of the reducing agent is hydrazine sulphate, or ascorbic acid.

Arsenic is pre-separated from the main steel components by distillation in the form of trichloride of arsenic from hydrochloric acid solution in the presence of sulfate hydrazine and potassium bromide or by precipitation with thioacetamide as a sulfide in 0.5 mol/DMsulfuric acid solution in the presence of the collector of sulphide of copper and tartaric acid as complexing agents.

5.2 Equipment, chemicals, solutions

Spectrophotometer or photoelectrocolorimeter with all accessories.

Perchloric acid, H. C., a density of 1.51 g/cm, or h. e. a., a density of 1.22 g/cm.

Ethyl alcohol according to GOST 5962 or GOST 18300.

Ammonium molybdate according to GOST 3765, recrystallized from alcoholic solution.

Recrystallization of ammonium molybdate in 250 g of ammonium molybdate was dissolved in 400 cmof water at 70−80 °C. the Hot solution is filtered through filter «blue ribbon» in a glass contains 300 cmof ethyl alcohol. The solution was cooled and allowed to stand in running water for 1 h. Precipitated crystals are filtered off on a Buchner funnel with filter «white ribbon». The crystals are washed 2−3 times with ethanol in batches of 20−30 cmand dried in air.

Ammonium molybdate, solution 10 g/lsulfuric acid 2.5 mol/DM.

Hydrazine sulfate, a solution of 1.5 g/DM.

Molybdate-hydrazine reaction mixture: in a volumetric flask with a capacity of 1 DMpour 100 cmof ammonium molybdate solution, dilute with water to volume 900 cm, add 10 cmof hydrazine sulfate solution, made up to the mark with water and stirred; the reaction mixture was prepared on the day of application.

Chornobryvtsy reagent: 5 g of ammonium molybdate dissolved in 100 cmwater when it is heated, cooled. Then in a volumetric flask with a capacity of 1 DMpour 500 cmof water, 280 cmof perchloric acid h. d. a. or 230 cmof perchloric acid H. h and gradually with stirring enter solution of ammonium molybdate. The solution was topped to the mark with water and mix; prepared on the day of application.

Ascorbic acid, a solution of 5 g/DM; prepared on the day of application.

The rest of the reagents, equipment and solutions — for 4.2.

5.3 analysis

5.3.1 Preparation of test solution

Weigh a portion of the sample in accordance with table 3. Weighing results in grams is recorded with precision to the fourth decimal place. The sample is placed in a beaker (or flask) with a capacity of 250−300 cm.

Table 3

Then do as specified in 4.3.1, 4.3.1.1, 4.3.1.2, separating the arsenic from the basic components of steel as a sulfide by thioacetamide or by distillation.

The test solution prepared according to 4.3.1.1 or 4.3.1.2, evaporated to a volume of 30−40 cm.

When the mass fraction of arsenic from 0.02% to 0.2% solution transferred to a volumetric flask with a capacity of 50 cm, made up to the mark with water and mix. Aliquot part of the solution 25−5 cm(table 3) were placed in a glass with a capacity of 100 cm.

To the solution was added 2 cmof perchloric acid and evaporated until the appearance of fumes of perchloric acid.

Warning: avoid contact of the vapors of perchloric acid with organic materials, ammonia and the vapors of nitrous acid.

The side of the Cup then rinsed with water and repeat evaporation to fumes of perchloric acid.

5.3.2 Spectrophotometric measurement

5.3.2.1 Determination of arsenic molybdate-gerasimovoj the reaction mixture

To the residue obtained by 5.3.1, poured 20 cmmolibdate-gerasimovoj the reaction mixture, the beaker cover watch glass and heated in a boiling water bath for 10 min. the Solution was cooled, transferred to a volumetric flask with a capacity of 50 cm. The walls of the beaker and the watch glass rinsed molybdate-gerasimovoj the reaction mixture, the contents of the volumetric flasks were topped up to the mark the same reaction mixture and stirred.

After 30 min measure the optical density of colored solution with spectrophotometer at a wavelength of 840 nm or photoelectrocolorimeter in a region of absorption from 750 to 900 nm. The thickness of the light absorbing layer is chosen so to obtain the optimal value of optical density.

As a solution comparison, use water.

The mass of arsenic found at the calibration schedule subject to amendments the reference experiment.

5.3.2.2 Determination of arsenic chlorotoluidines reagent

To the residue obtained by 5.3.1, poured 20 cmchlorotoluidines reagent, 1 cmof sulfuric acid solution of hydrazine or 1 cmof a solution of ascorbic acid, stirred and heated solution in a boiling water bath for 10−15 min. the Solution was cooled, transferred to a volumetric flask with a capacity of 50 cm, made up to the mark chlorotoluidines reagent and mix.

The optical density of colored solution is measured on the spectrophotometer at a wavelength of 840 nm or photoelectrocolorimeter in a field of light transmission from 750 to 900 nm.

The thickness of the light absorbing layer of the cell is chosen so to obtain the optimal value of optical density.

As a solution comparison, use water.

The mass of arsenic found at the calibration schedule subject to amendments the reference experiment.

5.3.3 Construction of calibration curve

In the beakers (or flasks) with a capacity of 250−300 cmis placed sample of carbonyl iron in the amount corresponding to the weight of the sample (table 3), and measured amount of a standard solution of arsenic A or B (table 4).

Table 4

All the glasses are poured acid as the dissolution of the sample, and further receives, as specified in 5.3.1 and 5.3.2.

From the values of absorbance of analyzed solutions is subtracted the value of the optical density of the solution in the reference experiment. On the found values of optical density and corresponding mass of arsenic build the calibration graph.

6 Potentiometric method for the determination of arsenic

6.1 the essence of the method

The method is based on potentiometric titration of arsenic (III) solution of potassium polnovatogo to obtain the jump in the potential. Arsenic is pre-separated from the main steel components by distillation in the form of trichloride of arsenic from hydrochloric acid solution in the presence of potassium bromide and hydrazine sulfate.

6.2 Apparatus, reagents and solutions

The setup for potentiometric titration:

a pair of electrodes — a platinum indicator and calomel reference electrode or tungsten;

magnetic or mechanical stirrer;

the DC millivoltmeter or pH meter that clearly capture the potential jump at the end point. If necessary, the instrument sequentially connecting a variable resistance, allows measurement of the full scale range of the device.

Potassium branovitsky according to GOST 4457, solution concentration of 0.01 mol/DM: 0,2783 g previously recrystallized from water solution and dried at 150−180 °C polnovatogo potassium is dissolved in 100−120 cmof water is poured into a measuring flask with a capacity of 1 DM, made up to the mark with water and mix. Allowed preparation of the solution of fiksanala. Mass concentration of solution polnovatogo potassium (g/cmarsenic) is 0,0003746.

The rest of the reagents, equipment and solutions — for 4.2.

6.3 analysis

6.3.1 Preparation of test solution

Weigh a portion of sample weighing 2 g and weighing results in grams is recorded with a precision of the fourth sign.

The sample is placed in a beaker (or flask) with a capacity of 600 cm, flow 60 cmof a mixture of hydrochloric and nitric acids (3:1) and 25−30 cmof sulfuric acid. If the steel contains tungsten, add 30 cmof phosphoric acid (1:1). A glass (or flask) watch glass cover and conduct dissolution initially at room temperature, and then moderately heated until complete dissolution of the sample.

Rinse watch glass with a little water and evaporate the solution prior to the allocation of sulphuric acid fumes. The contents of the beaker (or flask) cool, cautiously add 100 cmof hydrochloric acid (1:1) and quantitatively transfer the solution into the flask of the apparatus for the separation of arsenic with a capacity of 250 cm. To the solution was added 1 g of potassium bromide, 3 g of hydrazine sulfate and slowly distilled arsenic trichloride, heating the solution at 110−120 °C. the Distillate is collected in a glass receiver with a capacity of 400 cm, containing 40 cmof water. Distillation continued until until the receiver will not pass the initial volume of the solution.

6.3.2 Titrimetric procedure

The glass of the distillate is placed in a device for potentiometric titration, lower the stirrer and the electrodes and including a stirrer, stirred solution for 0.5−1 min. Then, without switching off the stirrer, the solution was titrated by adding dropwise a solution of potassium bromoperoxidase from microburette to obtain the jump in the potential.

7 Processing of results

7.1 Mass fraction of arsenic , %, calculated by the formulas:

in the determination of arsenic flameless atomic absorption and photometric methods

, (1)

where - the mass of arsenic, was found in the calibration schedule g;

the weight of steel, g;

in the determination of arsenic by potentiometric method

, (2)

where  — volume of the solution polnovatogo potassium, used for titration of the test solution, cm;

the volume of the solution polnovatogo potassium consumed for titration of the solution in the reference experiment, cm;

 — mass concentration of Bromeliaceae solution potassium with molar concentration of equivalent of 0.01 mol/DM, g/cmarsenic;

the weight of steel,

7.2 Standards of operational control of convergence, reproducibility, and accuracy of determining the mass fraction of arsenic is given in table 5.

Table 5

Standards of operational control of convergence and standards for control of reproducibility is calculated at a confidence level of 0.95. Standards of operational control precision is calculated at the confidence level of 0.85.

Algorithms for real-time control of measurement uncertainty and periodicity —
according to GOST 28473.