GOST 11739.7-99

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  ГОСТ 11739.7-99

GOST 11739.7−99 Alloys aluminum casting and wrought. Methods for determination of silicon

GOST 11739.7−99

Group B59

INTERSTATE STANDARD

ALLOYS ALUMINIUM CAST AND WROUGHT
Methods for determination of silicon

Aluminium casting and wrought alloys. Methods for determination of silicon

ISS 77.120.10
AXTU 1709

Date of introduction 2000−03−01

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 (minutes N 15 of 28 may 1999)

The adoption voted:

3 Resolution of the State Committee of the Russian Federation on standardization and Metrology from September 6, 1999 N 288-St inter-state standard GOST 11739.7−99 introduced directly as state standard of the Russian Federation from March 1, 2000

4 REPLACE GOST 11739.7−82

5 REISSUE. July 2003

1 Scope

This standard specifies the photometric (with a mass fraction of silicon from 0.02 to 1.0%), gravimetric (when the mass fraction of silicon from 0.3 to 25.0%) and atomic absorption (at a mass fraction of silicon from 0.10 to 1.0% and from 1.0 to 25.0%) methods for determination of silicon.

2 Normative references

The present standard features references to the following standards:

GOST 83−79 Sodium carbonate. Specifications

GOST 195−77 Sodium sanitarily. Specifications

GOST 2062−77 Acid methyl and hydrogen. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3765−78 Ammonium molybdate. Specifications

GOST 4109−79 Bromine. Specifications

GOST 4197−74 Sodium atomistically. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4221−76 Potassium carbonate. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 5457−75 Acetylene, dissolved and gaseous. Specifications

GOST 5817−77 tartaric Acid. Specifications

GOST 9428−73 Silicon (IV) oxide. Specifications

GOST 9656−75 boric Acid. Specifications

GOST 10484−78 hydrofluoric Acid. Specifications

GOST 10929−76 Hydrogen peroxide. Specifications

GOST 10931−74 Sodium molybdate 2-water. Specifications

GOST 11069−2001 primary Aluminium. Brand

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

GOST 18300−87 ethyl rectified technical. 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 add:

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 silicon

4.1 the essence of the method

The method is based on dissolving the sample in sodium hydroxide solution in the presence of hydrogen peroxide, the formation of the yellow form kremneftoristogo acid at the pH of the solution (1,0±0,1), the restoration of its ascorbic acid or 1-amino-2-naphthol-4-sulfonic acid to form a blue kremneftoristogo acid and measuring the optical density of the solution at a wavelength of 810 nm.

4.2 Equipment, reagents and solutions

Spectrophotometer.

Oven muffle.

Drying oven with thermostat.

a pH meter.

Bidistilled water, and stored in a plastic container.

Sodium hydroxide according to GOST 4328, store in plastic packaging; solution molar concentration of 8 mol/DM, cook and store in a plastic container: 320 g of sodium hydroxide is placed in a vessel with a capacity of 1000 cm, poured carefully, portions, when cooling 800 cmof water, after complete dissolution is cooled, top up with water to 1000 cmand mixed.

The molar concentration of the sodium hydroxide solution set so that 10.0 cmsolution was adequate (10,0±0,1) cmof a solution of nitric acid molar concentration of 8 mol/DM.

In a conical flask with a capacity of 250 cmis placed 10.0 cmof sodium hydroxide solution, poured 100 cmof water, add two drops of methyl red indicator and titrated with a solution of nitric acid before transition of yellow colouring of the solution, in crimson.

Nitric acid according to GOST 4461 density of 1,35−1,40 g/cm, the solution molar concentration of 8 mol/DM: 540 cmof nitric acid was placed in a volumetric flask with a capacity of 1000 cm, made up to the mark with water and mix.

The molar concentration of nitric acid is set as follows: in a conical flask with a capacity of 250 cmis placed 10,600 g of anhydrous sodium carbonate, poured 100 cmof water, after complete dissolution is cooled, add two drops of methyl red indicator and titrated with a solution of nitric acid before transition of yellow colouring of the solution, in crimson. The theoretical amount of nitric acid solution for the specified quantity of anhydrous sodium carbonate is equal to 25.0 cm. If necessary, the concentration of nitric acid solution is adjusted by adding water or acid to achieve the desired molar concentration.

The anhydrous sodium carbonate according to GOST 83 is dried in a drying Cabinet at a temperature of (110±2)°C for at least 1 h and store in desiccator or byxe.

Hydrochloric acid according to GOST 3118 density of 1.19 g/cm, a solution of 1:99 and the solution molar concentration of 4.4 mol/DM: 352 cmof hydrochloric acid is placed in a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

The molar concentration of hydrochloric acid is set so that 20.0 cmsolution was adequate (11,0±0,1) cmof sodium hydroxide solution.

In a conical flask with a capacity of 250 cmis placed 20.0 cmhydrochloric acid solution, poured to 100 cmof water, add two drops of methyl red indicator and titrate with sodium hydroxide solution of molar concentration of 8 mol/DMof transition to the crimson color of the solution yellow.

Sulfuric acid according to GOST 4204 density 1.84 g/cm, solution the molar concentration of 4 mol/DM: 225 cmof sulphuric acid carefully, a thin stream while stirring and cooling poured into a measuring flask with volume capacity of 1000 cm, containing 500 cmof water, cooled, made up to the mark with water and mix.

The molar concentration of the sulfuric acid solution is set so that 10.0 cmsolution was adequate (10,0±0,1) cmof sodium hydroxide solution.

In a conical flask with a capacity of 250 cmis placed 10.0 cmof a solution of sulfuric acid poured up to 100 cmof water, add two drops of methyl red indicator and titrate with sodium hydroxide solution of molar concentration of 8 mol/DMof transition to the crimson color of the solution yellow.

Ascorbic acid, a solution of 20 g/DM, freshly prepared: 2 g of ascorbic acid dissolved in water, the volume was adjusted to 100 cmand mixed.

Tartaric acid according to GOST 5817, a solution of 200 g/DM.

Sulphurous acid, saturated solution: prepare by passing to water sulphur dioxide to saturation.

Hydrogen peroxide according to GOST 10929.

Sodium sanitarily according to GOST 195.

Sodium pyrosulfite according to GOST 11683, solution 112,5 g/DM: 90 g of sodium pyrosulphite dissolved in 800 cmof water.

Sodium atomistically according to GOST 4197, solution 20 g/DM.

1-amino-2-naphthol-4-sulfonic acid: 14 g semitecolo sodium is placed in a conical flask with a capacity of 1000 cm, dissolved in 100 cmof water, add 1.5 g of 1-amino-2-naphthol-4-sulfonic acid and 800 cmof a solution of sodium pyrosulfite. The solution was filtered through a filter medium density (white ribbon) in a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix. The prepared solution stored in a flask made of dark glass and use within 1 month.

Potassium carbonate according to GOST 4221.

The background solution (basic solution)

Getting a background solution (fundamental solution) for calibration curve: polyethylene vessel with a capacity of 400 cmis placed 40,0 cmof sodium hydroxide solution, pour 200cmof water, 54.0 cmof a solution of nitric acid and 40.0 cmsolution of hydrochloric acid. After cooling, the solution was transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

Ammonium molybdate according to GOST 3765, recrystallized, solution 106 g/DMwith a pH of 7.2: 53 g ammonium molybdate was placed in a beaker with capacity of 500 cm, 250 cm pouredwater, 30 cmof sodium hydroxide solution, cooled to room temperature, top up with water to 350 cmand mixed. PH (7,2±0,1) are installed using a pH meter by adding dropwise with stirring a solution of sodium hydroxide. The resulting solution was filtered in a volumetric flask with a capacity of 500 cm, the filter was washed 2−3 times with water, made up to the mark with water and mix. Store 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 with stirring stick, 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, and dried in air for 8−10 hours

The technical rectified ethyl alcohol according to GOST 18300.

Sodium molybdate 2-water according to GOST 10931, a solution of 145 g/DM: 145 g of reagent was dissolved in 700 cmof hot water, cooled to room temperature and filtered through a filter medium density («white ribbon»), washing with cold water in a measuring flask with volume capacity of 1000 cm. Top up with water to the mark, stirred and transferred to plastic dishes. the pH of the solution should be not more than 8, set it using the pH meter.

Ammonia water according to GOST 3760.

Methyl red, solution 0,2 g/DM: 0.02 g of the reagent was placed in a conical flask with a capacity of 100 cmand dissolved in 60 cmof ethanol. The solution was transferred to volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Adsorbent (materiana paper): 100 g of crushed filters (red ribbon) is placed in a beaker with a capacity of 500 cm, 300 cm pouredhot water and stirred with a stirrer to obtain a homogeneous mass.

Silicon (IV) oxide according to GOST 9428.

Standard solutions of silica, prepared by one of the following ways.

Solution a: 0,2140 g of silicon oxide (IV), previously calcined in a muffle furnace at a temperature of (1000±10)°C for 30 min, placed in a platinum crucible and fused with 2 g of a mixture of sodium carbonate and potassium carbonate, taken in equal quantities in a muffle furnace at the temperature (700±10)°C to obtain a transparent mass.

After cooling to room temperature, the melt leached with water, the resulting solution was transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix. The solution is prepared and stored in a plastic container.

1 cmof the solution contains 0.0001 gram of silicon.

Solution B: 10 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 immediately before use in a plastic container.

1 cmof the solution contains 0,00001 g of silicon.

Sodium meta-silicate 9-water [1].
________________
* POS. [1]-[2], see Bibliography. — Note the manufacturer’s database.


Solution a: 1 g of sodium silicate were placed in a glass with a capacity of 400 cm, dissolved in 100 cmof water, poured 1 cmof sodium hydroxide solution and filtered through a thick folded filter («blue ribbon») in a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix. The solution is prepared and stored in a plastic container.

1 cmof the solution contains 0.0001 gram of silicon.

To establish the mass concentration of the silicon aliquot part of the solution is 50 cmis placed in a porcelain Cup with a capacity of 200 cm, flow 10 cmof hydrochloric acid, stirred, evaporated to dryness, poured 10 cmof hydrochloric acid and again evaporated to dryness. To the dry residue poured 10 cmof hydrochloric acid, 100 CCof hot water, stirred and incubated for 40 min at a temperature of 50−60°C for coagulation of the precipitate. The precipitate was filtered off through a filter medium density («white ribbon») with the adsorbent prepared according to 5.2, and washed eight times with hot hydrochloric acid 1:99.

The filter with the sediment is dried, incinerated in a platinum crucible and calcined in a muffle furnace at a temperature of 1000−1100°C for 30 min, the Crucible was cooled to room temperature and weighed. Then, to the residue in the crucible is added using a plastic pipette, ten drops of hydrofluoric acid, one drop sulfuric acid and heated to stop the allocation of white fumes of sulfuric acid. The crucible with the residue is again calcined in a muffle furnace at a temperature of 1000−1100°C for 10 min, cooled to room temperature and weighed.

The mass concentration of silicon , g/cm, is calculated by the formula

, (1)

where is the mass of the sludge before treatment with hydrofluoric acid, g;

 — the mass of the precipitate after treatment with hydrofluoric acid, g;

0,4675 — the ratio of silicon dioxide on silicon;

 — the volume of a standard solution taken for the determination of silicon, cm.

Solution B: 10 cmsolution Andtransferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix. The solution is prepared immediately before use in a plastic container, the mass concentration of the solution Andcalculated by the formula 1.

1 cmof the solution contains 0,00001 g of silicon.

Hydrofluoric acid according to GOST 10484.

4.3 analysis

4.3.1 the sample the sample weight of 0.25 g was placed in a platinum Cup or glass of glassy carbon with a capacity of 100 cm, pour the 10.0 cmof sodium hydroxide solution, covered with a platinum lid and heated to full dissolution, without leading up to boiling and avoiding splashing. Pour 1 cmof hydrogen peroxide, slide the cover and gently evaporated to a syrupy state of solution. After cooling to room temperature, the lid and the walls of the Cup is washed with 30 cmof hot water and heat, without boiling, before the separation of the hardened mass from the walls of the Cup. Then pour the 75−80 cmof hot water and heat for 15−20 min to dissolve the salts, not bringing the solution to boiling.

After cooling to room temperature, the solution was transferred to a glass beaker with a capacity of 400 cm, 17.0 cm containingnitric acid, 10.0 cmof a hydrochloric acid solution of 4.4 mol/DMand 50 cmof warm water, stirring with a plastic stick. Transfusion of alkaline solution should avoid contact of this solution with the walls of the glass beaker. If the sample contains more than 0.5% of manganese hydroxide and manganese are selected and deposited on the walls of the platinum Cup or glass of glassy carbon, then they pour a little acid solution from the glass Cup, add a few drops (1−3 drops) sulfurous acid or a solution of sodium attestatio and stirred the rotational motion to dissolve the hydroxide of manganese.

The solution is poured into a glass Cup, and platinum Cup or glass of glassy carbon was washed 2−3 times with hot water. The amount of the acid solution in a glass beaker was adjusted to 180 cm, is heated almost to boiling, if necessary, add another 1−2 drops of solution of sulphurous acid or sodium attestatio to completely dissolve the manganese hydroxide and boil under low heat for 10−15 C. the Solution was cooled to room temperature, transferred to a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix.

In the presence of turbidity associated with the presence of a large number of titanium, the solution is filtered through a dense filter («blue ribbon») in a dry conical flask.

4.3.2 Aliquot part of the test solution and of the solution of the control experience that complements aliquot part to a volume of 50 cmin accordance with table 1 was placed in a volumetric flask with a capacity of 100 cm, flow 15 cmwater and 5 cmof a solution of molybdate of ammonium or of sodium and stirred.


Table 1

The solution is allowed to stand for 10 min, pour 5 cmof a solution of tartaric acid, 15 cmof sulfuric acid solution, 5 cmsolution of 1-amino-2-naphthol-4-sulfonic acid or 5 cmof a solution of ascorbic acid, made up to the mark with water and mix.

4.3.3 Solution of the reference experiment are prepared according to 4.3.1 with all applicable in the analysis of reagents in at least three parallel definitions, but reduced to 13.5 cmwith a volume of nitric acid.

Aliquot part of the solution in the reference experiment of 50 cmis transferred to a volumetric flask with a capacity of 100 cmand continue in 4.3.2.

4.3.4 the Optical density of test solution and control solution experience is measured after 10 minutes, but no later than 40 minutes at a temperature of 20−30°C the wavelength of 810 nm in a cuvette with a layer thickness of 20 mm with a mass fraction of silicon is less than 0.1% or 10 mm when the mass fraction of silicon greater than 0.1%. Solution comparison is water.

Note — the Reagents and double-distilled water used in the analysis must have a degree of contamination of the silicon to optical density of the solution in the reference experiment does not exceed one fifth of the optical density of test solution.

4.3.5. The mass of silicon is determined according to the calibration schedule of the subtracting optical density of the test sample optical density of the solution in the reference experiment.

4.3.6. Construction of calibration curve

Eight volumetric flasks with a capacity of 100 cmeach placed 25 cmof a solution of the background (the main solution), seven of them measure 0,5; 1,0; 2,0; 4,0; 6,0; 8,0; 10,0 cmstandard solution B or B, which corresponds to 0,000005; 0,00001; 0,00002; 0,00004; 0,00006; 0,00008; 0,0001 g silicon, in all flasks is poured from the burette with water to a volume of 65 cm, poured 5cmof sodium molybdate or ammonium and incubated the solution for 10 min, add 5 cmof a solution of tartaric acid and further arrive at 4.3.2 and 4.3.4. Solution comparison is the solution, in which silicon is not introduced.

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

4.4 Processing of results

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

, (2)

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

 — the weight of the portion of the sample in aliquote part of the solution,

4.4.2 discrepancies in the results must not exceed the values given in table 2.


Table 2

Percentage

5 Gravimetric method for determination of silicon

5.1 the essence of the method

The method is based on decomposition of samples by sodium hydroxide in the presence of hydrogen peroxide, the formation of insoluble silicic acid after evaporation with perchloric or sulfuric acids, the calcination residue at a temperature of 1100 °C, removing the resulting silicon dioxide with hydrofluoric acid, weighing the residue and calculating the mass fraction of silicon in the mass difference.

5.2 the Instrument, reagents and solutions

Oven muffle.

Drying oven with thermostat.

Sodium hydroxide according to GOST 4328 (keep in plastic packaging) and a solution of molar concentration of 1.25 mol/l: 50 g of sodium hydroxide was placed in a polyethylene beaker with a capacity of 500 cm, poured carefully, under cooling and stirring, 300 cmof water, transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix. Store in a plastic container.

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

Hydrochloric acid according to GOST 3118 density of 1.19 g/cm, the solution molar concentration of 0.62 mol/l: 50 cmhydrochloric acid is placed in a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

Hydrofluoric acid according to GOST 10484, solution 1:4.

Bromatologia acid according to GOST 2062.

Bromine according to GOST 4109.

Bromine water, saturated solution: 50 g of bromine are placed in a measuring flask with volume capacity of 1000 cm, equipped with a glass stopper, pour 500 cmof water and shake 8−10 times, made up to the mark with water and stir a few times to reveal a tube.

Acid chloride [2] with a density of 1.67 g/cmand the solution molar concentration of 4 mol/DM: 350 cmof perchloric acid were placed in a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

Sulfuric acid according to GOST 4204 density 1.84 g/cm, a solution of 1:1.

Hydrogen peroxide according to GOST 10929.

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

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.

Adsorbent (materiana paper): 100 g of crushed filters (red ribbon) is placed in a beaker with a capacity of 500 cm, 300 cm pouredhot water and stirred with a stirrer to obtain a homogeneous mass.

5.3 analysis

5.3.1 Sample the sample weight in accordance with table 3 was placed in a Nickel, silver or glassy carbon Cup with a capacity of 250 cm, cover with a lid and dissolve one of the following ways: the mass percentage of silicon less than 5% in a Cup put a sample of sodium hydroxide and then with continuous cooling, carefully, in small portions pour the water in accordance with table 3; when the mass fraction of silicon of more than 5% and the presence of the large alloy content of magnesium or lithium to charge the samples first, carefully pour the sodium hydroxide solution and after the reaction is added a portion of sodium hydroxide in accordance with table 3.

Table 3

After termination of the reaction the cover and the walls of the Cup is washed with the minimum amount of hot water and avoiding splashing, heated to complete dissolution. Cautiously evaporated to a syrupy state of solution, is cooled, add 5−6 cmof hydrogen peroxide, and again evaporated to a syrupy condition. If necessary, treatment with hydrogen peroxide again. The solution is poured into 100 cmof hot water and heated to dissolve the salts.

5.3.2 Silicic acid isolated by evaporation with sulfuric or perchloric acid.

5.3.2.1 Evaporation with perchloric acid

The cooled solution obtained in 5.3.1, quantitatively transferred to a beaker with a capacity of 400 cm, containing 5 cmof nitric acid, perchloric acid and water in accordance with table 3. Cup and lid is washed with hot water and 10 cmof hydrochloric acid, adding the washings to the main solution, and stirred. In the presence of a brown precipitate of manganese dioxide is added hydrogen peroxide to dissolve the residue. Beaker cover watch glass, and evaporated until the appearance of white fumes of perchloric acid and continue steaming for 15−20 min. After cooling, pour 200 cmof hot water, mix thoroughly and heat to dissolve the salts. In the presence of sediment of manganese dioxide, add a few drops of hydrogen peroxide. The solution is maintained at a low heat, without boiling, for 30 min.

5.3.2.2. If the alloy of tin and (or) antimony up to 1% solution obtained in 5.3.1, quantitatively transferred to a beaker with a capacity of 400 cm, containing chloric acid and water in accordance with table 3. Cup and lid is washed with hot water and 10 cmof hydrochloric acid, adding the washings to the main solution, and stirred. In the presence of a brown precipitate of manganese dioxide is added dropwise hydrogen peroxide to dissolve the residue. The solution was heated for 3−5 min, carefully, in a fume hood pour the bromine and water bromatological acid in accordance with table 3, is evaporated until the appearance of white fumes of perchloric acid and continue the evaporation for 5 minutes, the Beaker cover watch glass, and continue the steaming for 15−20 min. After cooling, pour 200 cmof hot water and continue 5.3.2.1.

5.3.2.3. Evaporation with sulphuric acid

The cooled solution obtained in 5.3.1, transferred in a beaker with a capacity of 400 cm, containing 5 cmof nitric acid and sulfuric acid in accordance with table 3. Cup and lid is washed with hot water, and the solution was stirred in the presence of sediment of manganese dioxide are added dropwise hydrogen peroxide to dissolve the residue. The solution was evaporated until the appearance of white fumes of sulfuric acid, and continue the steaming for 15−20 min.

To the cooled residue cautiously, in portions, with continuous stirring, pour 200 cmof hot water and heated to dissolve the salts. In the presence of sediment of manganese dioxide, add a few drops of hydrogen peroxide. The solution is maintained at a low heat, without boiling, for 30 min.

5.3.3 the Solution obtained in 5.3.2.1−5.3.2.3, filtered through the filter medium density («white ribbon») with the adsorbent (filter A), washed 5−6 times with hot hydrochloric acid and hot water (until the red color of Congo paper, is placed on the edge of the filter), collecting the filtrate and washings in the same beaker.

5.3.3.1 When the mass fraction of silicon of more than 5%, a second processing of the filtrate obtained in 5.3.3. To do this, the filtrate and washings evaporated until the appearance of fumes of perchloric acid or sulfuric acid, and continue the steaming for 15−20 min. the cooled solution with continuous stirring gently poured 200 cmhot water heat, without boiling, for 30 min, filtered through a medium density filter (white ribbon) with the adsorbent (filter ).

5.3.4. The filter or filters A and B are placed in calcined at a temperature of 1000−1100°C for 30 min, cooled, brought to a constant weight platinum crucible, dried, carefully incinerated at a temperature of 500−600°C, not allowing them to ignite paper filter, calcined in a muffle furnace at a temperature of 1000−1100°C for 1 h, cooled in a desiccator and weighed. To the residue in the crucible is poured 0.5 cmof sulfuric acid solution, 3−5 cmhydrofluoric acid, evaporated to dryness, calcined in a muffle furnace at the same temperature for 5−10 min to constant weight, cooled in a desiccator and weighed. If necessary, the processing of hydrofluoric acid repeat.

5.3.5. Control the experience with all used during the analysis reagents are prepared according to 5.3.1−5.3.4.

5.4 processing of the results

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

, (3)

where is the mass of the crucible with the sediment prior to the removal of silica, g;

 — weight of crucible and residue after removal of silica, g;

 — the mass of the crucible with the sediment prior to the removal of silicon dioxide in a control experiment, g;

 — weight of crucible and residue after removal of silica in a control experiment, g;

0,4675 — the ratio of silicon dioxide on silicon;

 — the weight of the portion of the sample,

5.4.2 the Divergence of results should not exceed the values given in table 4.


Table 4

Percentage

6 Atomic absorption method for determination of silicon (with a mass fraction of silicon from 0.10 to 1.0%)

6.1 the essence of the method

The method is based on dissolving the samples in hydrochloric acid in the presence of nitric acid, the formation of the fluoride complex of silicon at room temperature and measuring the nuclear absorption of silicon at a wavelength of 251,6 nm in a flame acetylene-nitrous oxide.

6.2 Apparatus, reagents and solutions

Spectrophotometer of atomic absorption with a radiation source for silicon.

Acetylene according to GOST 5457.

Nitrous oxide medical.

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

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

Boric acid according to GOST 9656.

Hydrofluoric acid according to GOST 10484.

Acid bridgestation: 280 cmhydrofluoric acid at a temperature of (10±2)°C add portions 130 g of boric acid and stirred. The solution is prepared and stored in a plastic container.

Aluminium metal according to GOST 11069 brand А999.

Sodium hydroxide according to GOST 4328, a solution of 30 g/DM.

Sodium meta-silicate 9-water [1].

Standard solution silicon: 10,112 g of sodium silicate dissolved in Teflon beaker in 100 cmof water with moderate heating, the solution was transferred into a measuring flask with volume capacity of 1000 cm, add 2 cmof sodium hydroxide solution, made up to the mark with water and mix. The solution was stored in a plastic container.

1 cmof the solution contains 0.001 g of silicon.

To establish the mass concentration of the silicon aliquot part of the solution is 25 cmis placed in a porcelain Cup with a capacity of 200 cmand further operations are carried out at 4.2.

6.3 analysis

6.3.1 Sample the sample weight of 0.5 g was placed in Teflon beaker with a capacity of 100 cm, moisten the sample with about 10 cmof water and add portions 25 cmhydrochloric acid solution. The dissolution is carried out at room temperature. After dissolution of the sample add 2 cmof nitric acid, the solution was stirred, heated to boiling and boiled for 1−2 min.

After cooling to room temperature the solution was added 10 cmbridgestation acid and transferred the solution into a measuring flask with a capacity of 100 cm, made up to the mark with water and mix. The solution was then poured into the same beaker in which the dissolution was carried out.

6.3.2 Solutions of the reference experiment 6.3.1 cooked with all used during the analysis reagents.

6.3.3 Construction of calibration curve

Seven Teflon beakers with a capacity of 100 cmeach placed 0.5 g of metal aluminum, moistened with approximately 10 cmof water, five of them measure 0,5; 1,0; 2,5; 3,5; 5,0 cmstandard solution silicon, which corresponds to 0,0005; 0,001; 0,0025; 0,0035; 0.005 g of silica, and carry out the dissolution and subsequent operations in accordance with 6.3.1.

6.3.4 the sample Solution, solution control experience and solutions to build the calibration curve is sprayed in a reducing flame acetylene-nitrous oxide and measure the atomic absorption of silicon at a wavelength of 251,6 nm.

According to the obtained values of atomic absorption and corresponding mass concentrations of silicon to build a calibration curve in the coordinates: «the Value of atomic absorption — mass concentration of silicon, g/cm». Solutions that are not introduced silica, are the solutions of the control experience in the construction of calibration curve.

The mass concentration of silicon in solutions of the sample solution and the reference experiment is determined by the calibration schedule.

6.4 Processing of results

6.4.1 Mass fraction of silicon , %, is calculated by the formula

, (4)

where is the mass concentration of silicon in the sample solution found by the calibration schedule, g/cm;

 — mass concentration of silicon in solution in the reference experiment, was found in the calibration schedule, g/cm.

 — the volume of the sample solution, cm;

 — the weight of the portion in the sample solution,

6.4.2 Divergence of results should not exceed the values given in table 5.


Table 5

Percentage

7 Atomic absorption method for determination of silicon (with a mass fraction of silicon from 1.0 to 25.0%)

7.1 the essence of the method

The method is based on dissolving the sample in sodium hydroxide solution and measuring the nuclear absorption of silicon at a wavelength of 251,6 nm in a flame acetylene-nitrous oxide.

7.2 Apparatus, reagents and solutions

Spectrophotometer of atomic absorption with a radiation source for silicon.

Acetylene according to GOST 5457.

Nitrous oxide medical.

Sodium hydroxide according to GOST 4328, a solution of 300 g/DM; prepare and store in a plastic container.

Hydrogen peroxide according to GOST 10929.

Sodium meta-silicate 9-water [1].

Aluminium metal according to GOST 11069 brand А999.

Standard solutions of silicon.

Solution a: 10,112 g of sodium silicate dissolved in 50 cmof water in Teflon beaker with a capacity of 100 cmwith moderate warming. The solution was transferred to volumetric flask with a capacity of 100 cm, add 2 cmof sodium hydroxide solution, made up to the mark with water and mix. The solution was stored in a plastic container.

1 cmof the solution contains 0.01 g of silicon.

To establish the mass concentration of the silicon aliquot part of the solution 2 cmplaced in a porcelain Cup with a capacity of 200 cmand carry out further operation on the 4.2.

Solution B: 50 cmsolution And the mass concentration computed by the formula 1, is transferred into a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix. The solution is prepared immediately before use.

1 cmof the solution contains 0.005 g of silicon.

7.3 analysis

7.3.1 a portion of the alloy by mass in accordance with table 6 was placed in Teflon beaker with a capacity of 100 cm, poured 30 cmof sodium hydroxide solution and dissolved at room temperature in order to avoid losses if possible spray Cup cover PTFE cap, the solution is heated and boiled for 15 min.

To the cooled to room temperature, the solution was added dropwise 2 cmof hydrogen peroxide. Then the solution in a beaker covered with a lid, boil for 3−5 min. After cooling to room temperature, thoroughly washed with water cover and the walls of the beaker and transfer the solution into a measuring flask with volume capacity in accordance with table 6, topped to the mark with water, mix and transfer the solution into a polyethylene vessel with a capacity of 300 cm.


Table 6

7.3.2 Solutions of the reference experiment is prepared according 7.3.1 with all used during the analysis reagents.

7.3.3 Construction of calibration graphs

7.3.3.1 When the mass fraction of silicon from 1.0 to 5.0%

Seven Teflon beakers with a capacity of 100 cmeach placed 0.5 g of metal aluminum, moisten it with 10 cmof water and in five of them measure 0,5; 1,0; 1,5; 2,0; 2,5 cmstandard solution A, which corresponds to 0,005; 0,01; 0,015; 0,02; 0,025 g of silicon, and then perform operations according to 7.3.1.

7.3.3.2 When the mass fraction of silicon, more than 5.0 to 10.0%

Six PTFE beakers with a capacity of 100 cmeach placed 0.25 g of aluminum metal, moisten it with 10 cmof water and four of them measure 1,0; 1,5; 2,0; 2,5 cmstandard solution A, which corresponds to 0,01; 0,015; 0,02; 0,025 g of silicon, and then perform operations according to 7.3.1.

7.3.3.3 If the mass fraction of silicon of more than 10.0 to 15.0%

Seven Teflon beakers with a capacity of 100 cmeach placed 0.2 g of metallic aluminum, moisten it with 10 cmof water and in five of them measure 4,0; 4,5; 5,0; 5,5; 6,0 cmstandard solution B, which corresponds to 0,02; 0,0225; 0,025; 0,0275; 0.03 g silicon, and further perform the operations 7.3.1.

7.3.3.4 When the mass fraction of silicon in excess of 15.0 to 25.0%

Six PTFE beakers with a capacity of 100 cmeach placed 0.1 g of metallic aluminium, moisten it with 10 cmof water and four of them measure 2,8; 3,6; 4,4; 5,2 cmstandard solution B, which corresponds to 0,014; 0,018; 0,022; 0,026 g of silicon, and then perform operations according to 7.3.1.

7.3.3.5 the sample Solution, the solutions in the reference experiment and the solutions for constructing the calibration curve is sprayed in a reducing flame acetylene-nitrous oxide and measure the atomic absorption of silicon at a wavelength of 251,6 nm.

According to the obtained values of the nuclear absorption of silicon and corresponding mass concentrations of silicon to build a calibration curve in the coordinates: «the Value of atomic absorption — mass concentration of silicon, g/cm». Solutions that are not introduced silica, are the solutions of the control experience in the construction of calibration curve.

The mass concentration of silicon in solutions of the sample solution and the reference experiment is determined by the calibration schedule.

7.4 processing of the results

7.4.1 Mass fraction of silicon , %, is calculated by the formula

, (5)

where is the mass concentration of silicon in the sample solution found by the calibration schedule, g/cm;

 — mass concentration of silicon in solution in the reference experiment, was found in the calibration schedule, g/cm;

 — the volume of the sample solution, cm;

 — the weight of the portion in the sample solution,

7.4.2 discrepancies in the results must not exceed the values given in table 7.

Table 7

Percentage

Annex a (informative). Bibliography

APPENDIX A
(reference)

[1] THE 6−09−5337−87* Sodium meta-silicate 9-water (JSC «Altaykhimprom» — Slavgorod, Altai Krai)
________________
* The one referred to here and hereinafter, not shown. For additional information, please refer to the link. — Note the manufacturer’s database.


[2] THE 6−09−2878−84 Acid chloride (Ural plant of chemical reagents — Verkhnyaya Pyshma, Sverdlovsk region)