GOST 11739.14-99

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  ГОСТ 11739.14-99

GOST 11739.14−99 Alloys aluminum casting and wrought. Methods for determination of arsenic

GOST 11739.14−99

Group B59

INTERSTATE STANDARD

ALLOYS ALUMINIUM CAST AND WROUGHT

Methods for determination of arsenic

Aluminium casting and wrought alloys.
Methods for determination of arsenic

ISS 77.120.10
AXTU 1709

Date of introduction 2000−09−01

Preface

1 DEVELOPED by JSC «Russian Institute of light alloys» (JSC VILS), the Interstate technical Committee for standardization MTK 297 «Materials and semi-finished products of light alloys"

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 16−99 dated 8 October 1999)

The adoption voted:

3 Resolution of the State Committee of the Russian Federation for standardization and Metrology dated February 18, 2000 N 41-St inter-state standard GOST 11739.14−99 introduced directly as state standard of the Russian Federation from September 1, 2000

4 REPLACE GOST 11739.14−82

1 Scope

This standard establishes photometric methods for determination of arsenic in aluminum casting and wrought alloys with the mass fraction of arsenic, respectively from 0.002% to 0.02% and from 0.002% to 0.04%.

2 Normative references

The present standard features references to the following standards:

GOST 1973−77 arsenious Anhydride. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3640−94 Zinc. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3765−78 Ammonium molybdate. Specifications

GOST 4159−79 Iodine. Specifications

GOST 4201−79 Sodium carbonate acidic. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4232−74 Potassium iodide. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 5841−74 Reagents. Hydrazine sulfate

GOST 10484−78 hydrofluoric Acid. Specifications

GOST 10929−76 Hydrogen peroxide. Specifications

GOST 11683−76 (ISO 3627−76) sodium Pyrosulfite technical. Specifications

GOST 14261−77 hydrochloric Acid of high purity. Specifications

GOST 18300−87 ethyl rectified technical. Specifications

GOST 20288−74 Carbon tetrachloride. Specifications

GOST 25086−87 non-ferrous metals and their alloys. General requirements for methods of analysis

3 General requirements

3.1 General requirements for methods of analysis GOST 25086 with the Supplement.

3.1.1 the result of the analysis be the arithmetic mean of results of two parallel measurements.

4 Photometric method for the determination of arsenic (in mass fraction of arsenic from 0.002% to 0.02%)

4.1 the essence of the method

The method is based on dissolving the samples in hydrochloric acid in the presence of hydrogen peroxide, the separation of arsenic from other components of the alloy Stripping ARSENICAL hydrogen education michalopolous of heteroalicyclic, restore her to her blue form a hydrazine sulfate in sulfuric acid solution of 0.12−0.2 mol/DM, and measuring the optical density of the solution at a wavelength of 800 nm.

4.2 Equipment, reagents and solutions

Spectrophotometer or photoelectrocolorimeter.

Apparatus for distillation of arsenic (figure 1).

Figure 1. Apparatus for distillation of arsenic

1 flat — bottomed flask with cone with a capacity of 50−100 cm; 2 — tube U-shaped curved
with a diameter of 5 mm with a drawn into the capillary end is attached to the cone to flat-bottomed flask 1;
3 — absorption vessel is a conical tube with a capacity of 10 cm;
4 — tube short glass with a diameter of 6−7 mm

Figure 1

Hydrochloric acid according to GOST 3118 density of 1.19 g/cmand a solution of 1:1.

Sulfuric acid according to GOST 4204 density 1.84 g/cmand a solution of 1:5 and 1 mol/DM.

Hydrogen peroxide according to GOST 10929.

Hydrazine sulfate according to GOST 5841, a solution of 1.5 g/DM.

Sodium carbonate acidic, GOST 4201, a solution of 0.5 mol/DM: 4.2 g of salt is dissolved in 50 cmof water, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Tin dichloride 2-water [1] (Appendix A), a solution of 500 g/DM: 50 g of tin dichloride was dissolved in 65 cmof hydrochloric acid, transferred into a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Potassium iodide according to GOST 4232 and a solution of 150 g/DM. Stored in a flask made of dark glass, protected from light.

Iodine GOST 4159, a solution of 2.5 g/DM: 0.25 g iodine and 0.4 g potassium iodide was placed in a volumetric flask with a glass stopper with a capacity of 100 cm, flow 10 cmof water, shake until complete dissolution of iodine, made up to the mark with water and mix. The solution was stored in a flask made of dark glass, protected from light.

The technical rectified ethyl alcohol according to GOST 18300.

Ammonia water according to GOST 3760.

Ammonium molybdate according to GOST 3765 recrystallized, a solution of 10 g/DM: 1 g ammonium molybdate dissolved in 10 cmof water, poured 90 cmof sulfuric acid solution 1:5 and stirred. The solution was stored in a plastic container.

For recrystallization 250 g ammonium molybdate was placed in a beaker with a capacity of 1 DM, pour 400 cmof water, heated to a temperature of (80±2) °C, dissolved under stirring with a glass rod, add ammonia until the smell and the hot solution is filtered through a dense filter («blue ribbon») in a glass contains 300 cmof ethyl alcohol. The solution is cooled to a temperature of (10±2) °C and allowed to settle for 1 h. Precipitated crystals are filtered off through a Buchner funnel, sucking mother liquor through the filter medium density («white ribbon»).

The crystals are washed three times with ethanol in portions of 30 cm, after which they are spread evenly on a sheet of filter paper covering the second sheet of paper, and dried in air for 8−10 hours

The mixture of reagents: 10 cmof a solution of molybdate of ammonium is placed in a volumetric flask with a capacity of 100 cm, flow 10 cmof hydrazine sulfate solution, made up to the mark with water and mix. The solution is prepared immediately before use.

Sodium sanitarily Piro according to GOST 11683, solution 50 g/lfreshly prepared.

Sodium hydroxide according to GOST 4328, solution 100 g/DM. Prepare and store in a plastic container.

Zinc GOST 3640 brand CV00.

To clean the surface of the granules are treated with hydrochloric acid, washed with water and stored in boxe with water until use.

The indicator Congo red: 0.1 g of the reagent dissolved in 100 cmof water at weak heating, the solution was cooled and stirred.

Indicator paper Congo: medium-density filters («white ribbon») is impregnated with a solution of the Congo, dried in a drying Cabinet at a temperature of 100−105 °C, sliced and stored in boxe. The paper is suitable for use within 1 month.

Arsenious anhydride according to GOST 1973.

Standard solutions of arsenic.

Solution a: 0,1320 g of arsenious anhydride are placed in a conical flask with a capacity of 100 cmand dissolved in 10 cmof sodium hydroxide solution. Pour a solution of hydrochloric acid until the red color of Congo paper violet, transferred to a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.0002 g of arsenic.

Solution B: 25 cmsolution And transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix. The solution is prepared before use.

1 cmof the solution

contains of 0.00005 g of arsenic.

4.3 analysis

4.3.1 the sample the sample weight of 0.5 g was placed in a flask with a capacity of 50−100 cmof the device for distillation of arsenic, poured 15 cmwater, 10 cmof hydrochloric acid solution and immediately close the flask with a U-shaped tube, the end of which is immersed in the absorption vessel containing 5 cmof iodine solution and 0.5 cmof a solution of sodium carbonic acid (absorbing solution).

After dissolving pour the 9.5 cmhydrochloric acid solution, 1 cmof hydrogen peroxide, are thoroughly mixed, pour 2 cmof a solution of potassium iodide, 5 min — 1 cmof a solution of tin dichloride and allowed to stand at room temperature for 30 min. Then the flask was quickly immersed nine pellets of zinc, immediately close the U-shaped tube and passed the hydrogen produced via the absorption solution for 1.5

h

4.3.2 Absorption solution is transferred to a volumetric flask with a capacity of 25 cm, 12.5 cm pour themixture of the reagents dropwise a solution of sodium semitecolo to the disappearance of color of iodine was stirred and heated in a boiling water bath for 15−20 min. the Solution was cooled, made up to the mark with water and mix.

4.3.3 Solution of the reference experiment is prepared in accordance with 4.3.1 and 4.3.2 all used during the analysis reagents.

4.3.4 the Optical density of the sample solution and control solution experience is measured at a wavelength of 800 nm in a cuvette with a layer thickness of 10 mm Solution comparison is water.

4.3.5 Mass of arsenic is determined by calibration schedule, subtracting out the optical density of the sample solution and the optical density of the solution in the reference experiment.

4.3.6 Construction of calibration curve

In seven of the eight volumetric flasks with a capacity of 25 cmeach measure 0,2; 0,4; 0,6; 0,8; 1,0; 1,5; 2,0 cmstandard solution B, which corresponds to 0,00001; 0,00002; 0,00003; 0,00004; 0,00005; 0,000075; 0,0001 g arsenic, pour 2.5 cmof iodine solution, a 0.5 cmof a solution of acidic sodium carbonate and then act on 4.3.2 and 4.3.4. Solution comparison is the solution in which the arsenic is not introduced.

According to the obtained values of optical density of the solutions and their corresponding mass of arsenic build the calibration graph.

4.4 Processing of results

4.4.1 Mass fraction of arsenic , %, is calculated by the formula

, (1)

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

 — the weight of the portion of the sample,

4.4.2 discrepancies in the results must not exceed the values given in table 1.


Table 1

Percentage

5 Photometric method for the determination of arsenic (in mass fraction of arsenic from 0.002% to 0.04%)

5.1 the essence of the method

The method is based on dissolving the samples in hydrochloric acid, extraction of the iodide of arsenic III carbon tetrachloride from a solution of hydrochloric acid of 9 mol/DM, the re-extraction of arsenic III water, the oxidation of arsenic to arsenic-IIl V iodine, the formation of arsenic-molybdenum complex with the restoration of its ascorbic acid to arsenic-molybdenum blue in the presence of a catalyst — potassium Armenonville and measuring the optical density of the solution at a wavelength of 800 nm.

5.2 the Instrument, reagents and solutions

Spectrophotometer or photoelectrocolorimeter.

Oven muffle.

Drying oven with thermostat.

Hydrochloric acid of high purity according to GOST 14261 density of 1.19 g/cmand a solution of 1:1 and 2:1.

Nitric acid according to GOST 4461 density of 1,35−1,40 g/cm, a solution of 1:1.

Sulfuric acid according to GOST 4204 density 1.84 g/cm, mortar 1:1 and 1 mol/DM.

Acids mixture: equal volumes of solutions of 1:1 sulphuric, nitric and hydrochloric acids.

Sodium hydroxide according to GOST 4328, solution 100 g/DM. Prepare and store in a plastic container.

Potassium iodide according to GOST 4232, a solution of 1 g/cm: 20 g of potassium iodide dissolved in 20 cmof water.

Iodine GOST 4159, saturated solution: 25 g of potassium iodide and 20 g of iodine placed in a flask with a glass stopper with a capacity of 250 cm, 70 cm pouredwater and shaken until complete dissolution of iodine, made up to the volume 250 cmwith water, add 1−2 g of iodine, is shaken and left overnight, the solution must be undissolved crystals of iodine. The solution was stored in a flask made of dark glass, protected from light.

Ascorbic acid, a solution of 4 g/DMfreshly prepared.

The technical rectified ethyl alcohol according to GOST 18300.

Ammonia water according to GOST 3760.

Hydrofluoric acid according to GOST 10484.

Ammonium molybdate according to GOST 3765 recrystallized, solution 7 g/DM: 3.5 g ammonium molybdate dissolved in 100 cmof solution sulfuric acid 1 mol/DM, is transferred into a volumetric flask with a capacity of 500 cm, made up with the same solution of sulfuric acid to the mark and mix.

The procedure for the recrystallization of the ammonium molybdate — 4.2.

Potassium armanavicius, a solution of 1.5 g/lfreshly prepared.

Carbon tetrachloride according to GOST 20288.

The indicator Congo red, 0.1 GM of reagent was dissolved in 100 cmof water at weak heating, the solution was cooled and stirred.

Indicator paper Congo: medium-density filters («white ribbon») is impregnated with a solution of the Congo, dried in a drying Cabinet at a temperature of 100−105 °C, sliced and stored in boxe. The paper is suitable for use within 1 month.

Arsenious anhydride according to GOST 1973.

Standard solutions of arsenic.

Solution a: 0,1320 g of arsenious anhydride are placed in a conical flask with a capacity of 100 cmand dissolved in 10 cmof sodium hydroxide solution. Pour a solution of hydrochloric acid 1:1 to change the red color of Congo paper lilac, cooled, transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.0001 g of arsenic.

Solution B: 10 cmsolution And transferred to a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof the solution contains 0,000002 grams of arsenic.

The solution is prepared

before use.

5.3 analysis

5.3.1 Sample the sample weight in accordance with table 2 is placed in a conical flask with a capacity of 250 cm, poured in small portions 40 cmof the mixture of acids and heated until dissolved.


Table 2

After the violent reaction add 5 or 10 cmof sulfuric acid solution 1:1 (depending on the mass of sample samples), evaporated with moderate heat to the advent of the white fumes of sulfuric acid and wet salts. The solution was cooled to room temperature, washed walls 20−30 cmof water, stirred and again evaporated to release vapors of sulfuric acid. To the cooled residue wet salts cautiously, with stirring, poured 20 cmof water, 40 cmof hydrochloric acid and heat, without boiling, to dissolve the salts.

5.3.2 When the mass fraction of silicon of more than 4% solution and the precipitate was filtered through a filter medium density («white ribbon»), washed the filter twice with 10 cmsolution of hydrochloric acid 2:1, collecting the filtrate and washings in a conical flask with a capacity of 250 cm(stock solution).

The filter with precipitate was placed in a platinum crucible, dried, incinerated, preventing ignition, and calcined at 500−600 °C for 2−3 min. After cooling in the crucible add five drops of sulfuric acid, 5 cmhydrofluoric acid and drop by drop nitric acid (approximately 1 cm) to obtain a transparent solution. The solution was evaporated to dryness, cooled, poured to the dry residue in the crucible is 5 cm.of hydrochloric acid 1:1 and dissolved under moderate heating. After cooling, the solution attached to the base solution in the conical flask.

5.3.3 Cooled solution was transferred to separatory funnel No. 1 with a capacity of 250 cm, washed the walls of the bulb 20 cmof hydrochloric acid, poured 1 cmof a solution of potassium iodide in 10 min 20 cmof carbon tetrachloride.

The solution was shaken for 1 min, allowed to settle and decanted the organic phase in a separatory funnel No. 2 with a capacity of 100 cm.

Re-extraction is carried out as in separating funnel N 1 with 20 cmof carbon tetrachloride for 1 min, pouring the organic phase into separatory funnel No. 2. The aqueous phase is discarded.

5.3.4 To the organic phase in a separating funnel N 2 flow of 20 cmof water, shaken for 1 min and after settling, the organic phase is discarded.

5.3.5 the Aqueous phase was transferred to volumetric flask with a capacity of 50 cmand poured dropwise a saturated solution of iodine to obtain a stable coloring of iodine. After 5 min, poured dropwise a solution of ascorbic acid with stirring until the disappearance of color of iodine; if in the solution there are drops of carbon tetrachloride, painted in pink color, then add three more drops of ascorbic acid solution and shaken until discoloration; poured 10 cmof a solution of molybdate of ammonium, 5 cmof ascorbic acid solution, 1 cmof a solution of potassium Armenonville, made up to the mark with water and mix.

5.3.6 Solution in the reference experiment is prepared in accordance with 5.3.1 to 5.3.5 with all used during the analysis reagents.

5.3.7 Optical density of test solution and control solution experience is measured after 40 min at a wavelength of 800 nm in a cuvette with a layer thickness of 50 mm. Solution of comparison is water.

5.3.8 Mass of arsenic is determined by calibration schedule by subtracting the optical density of test solution-optical density of the solution in the reference experiment.

5.3.9 Construction of calibration curve

In five out of six volumetric flasks with a capacity of 50 cmeach measure 2,0; 5,0; 10,0; 15,0; 20,0 cmstandard solution B, which corresponds to 0,000004; 0,00001; 0,00002; 0,00003; 0,00004 g of arsenic, and then continue on 5.3.5 and 5.3.7. Solution comparison is the solution in which the arsenic is not introduced.

According to the obtained values of optical density of the solutions and their corresponding mass of arsenic build the calibration graph.

5.4 processing of the results

5.4.1 Mass fraction of arsenic , %, is calculated by the formula

, (2)

where - the mass of arsenic in the sample solution found by the calibration schedule g;

 — the weight of the portion of the sample,

5.4.2 the Divergence of results should not exceed the values given in table 3.


Table 3

Percentage