GOST 12697.6-77

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  ГОСТ 12697.6-77

GOST 12697.6−77 Aluminum. Method for determination of silicon (with Amendments No. 1, 2, 3)

GOST 12697.6−77

Group B59

INTERSTATE STANDARD

ALUMINIUM

Method for determination of silicon

Aluminium. Method for determination of silicon

ISS 77.120.10
AXTU 1709

Date of introduction 1979−01−01

The decision of the State standards Committee of the Council of Ministers of the USSR from 27.09.77 N 2315 date of introduction is established 01.01.79

Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 5−6-93)

REPLACE GOST 12702−67 in part of sec. 2

EDITION with Amendments No. 1, 2, 3 approved in December 1980, November 1985, may 1988 (IUS 3−81, 2−86, 8−88).


This standard sets the photometric method for the determination of silicon in aluminum (with a mass fraction of silicon from 0.0005 to 1.0%).

The method is based on formation of colored complex compounds of silicon with ammonium molybdate, followed by reduction of the complex with ascorbic acid.

Photometric colored solution in the spectrophotometer at nm or photoelectrocolorimeter at nm.

(Changed edition, Rev. N 1, 3).

1. GENERAL REQUIREMENTS

1.1. General requirements for method of analysis according to GOST 12697.1−77 and GOST 25086−87.

(Changed edition, Rev. N 2, 3).

2. APPARATUS, REAGENTS AND SOLUTIONS

Types photoelectrocolorimeter FEK-56M, PEC-60, KLF or the types of spectrophotometer SF-16, SF-26 or similar type.

Laboratory scales according to GOST 24104−88* 2nd accuracy class with the weighing error of 0.0002 g.
__________________
* From 1 July 2002 was put into effect GOST 24104−2001** (here and below).

** On the territory of the Russian Federation GOST R 53228−2008, here and hereafter. — Note the manufacturer’s database.

Laboratory scales according to GOST 24104−88 with an accuracy of weighing to 0.01 g.

Laboratory autotransformer (Latr).

Muffle furnace with thermostat, providing a temperature of 1000 °C.

Aluminum brand А999 according to GOST 11069−2001.

Solution of aluminum with a mass fraction of 2%; prepared as follows: aluminium in the form of a rod is cleaned by boiling in hydrochloric acid, diluted 1:2 and then dissolved electrochemically in a 2.5 mol/DMnitric acid as specified in claim 3.1. Number of 2.5 mol/DMnitric acid take the rate of 45 cmper 1 g of aluminum. Dissolve about 10 g of aluminium.

The resulting solution is boiled, oxidized with potassium permanganate, transfer into a measuring flask with a capacity of 500 cm, is diluted to the mark with water and mix.

Ammonium molybdate according to GOST 3765−78, solutions with a mass fraction of 5% and a mass fraction of 10.6%. A solution with a mass fraction of 10.6% is prepared in the following way: 53 g of ammonium molybdate was placed in a polyethylene beaker, add 250 cmof water and 30 cm8 mol/DMsolution of sodium hydroxide, stirred and, if necessary, slightly warmed (40−50 °C) until complete dissolution, cooled and diluted with water to a volume of approximately 350 cm. With the help of a pH meter check the pH of the solution and, if necessary, add dropwise 8 mol/DMsolution of sodium hydroxide to establish the pH of the solution to 7±0,1. The solution was diluted to a volume of 400 cm, and then filtered through a filter of medium density in a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix. Keep the solution in a plastic vessel.

Double-distilled water. The second distillation is produced in a quartz container. The water is stored in containers of polyethylene or quartz. Used in the analysis of high-purity aluminium.

Potassium permanganate according to GOST 20490−75, a solution with a mass fraction of 0.02%.

Ascorbic acid, freshly prepared solution with a mass fraction of 2%.

Nitric acid of high purity according to GOST 11125−84, solutions 5 and 2.5 mol/DM.

Hydrochloric acid by the GOST 3118−77, diluted 1:2.

Sulfuric acid GOST 4204−77, solutions of 8.85, the 4.2 and 0.07 mol/DM.

Sodium hydroxide according to GOST 4328−77, solutions with a mass fraction of 20% and 0.5 mol/DM. Solutions of sodium hydroxide is prepared and stored in a plastic container.

Methyl orange, solution with a mass fraction of 0.1%.

Phenolphthalein, alcohol solution with a mass fraction of 1%.

Rectified ethyl alcohol GOST 18300−87.

The anhydrous sodium carbonate according to GOST 83−79.

The solution-background; prepared as follows: in a plastic container dissolve in water 25 g of sodium hydroxide. The cooled solution using plastic sticks poured into a glass with a capacity of 400 cm, containing 84 cm4 mol/DMsolution of sulphuric acid and 100 cmof water. The resulting solution was filtered in a volumetric flask with a capacity of 500 cm, is diluted to the mark with water and mix.

Silicon dioxide according to GOST 9428−73.

Solutions silicon standard.

Solution A, prepared as follows: 0,2140 g donkersteeg, pre-calcined at a temperature of 1000 °C silicon dioxide is fused in a platinum crucible with 5 g of sodium carbonate until a clear melt.

The smelt is dissolved in water by heating in a platinum Cup.

The solution was cooled, poured into a measuring flask with volume capacity of 1000 cm, is diluted to the mark with water and mix.

The solution was stored in a plastic container.

1 cmof the solution contains 0.1 mg of silicon (Si).

Solution B is prepared before use as follows: a pipette, take 25 cmof solution A in a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.01 mg of silicon (Si).

Solution; prepared before use as follows: a pipette, take 25 cmof solution A in a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.005 mg of silicon (Si).

Alkaline solutions are prepared and stored in vessels from which the silica is not leached (plastic, silver, etc. dishes).

Sodium sanitarily Piro (sodium metabisulphite).

1-amino-2-naphthol-4-sulfonic acid solution with a mass fraction of 0.16%. Semitecolo 0.8 g of sodium is dissolved in 10 cmof water, add 0.16 g 1-amino-2-naphthol-4-sulfonic acid and 50 cmof a solution containing 10 g of sodium metabisulfite. After stirring the solution was filtered in a volumetric flask with a capacity of 100 cm, wash the filter with water, then the solution in the flask made up to the mark and mix. The solution is prepared before use.

Alcohol n-butyl according to GOST 5208−81, distilled at a temperature of 117°.

Sodium sulfate, anhydrous GOST 4166−76.

Hydrogen peroxide according to GOST 10929−76, a solution with a mass fraction of 6%.

(Changed edition, Rev. N 1, 3).

3. ANALYSIS

3.1. Weighed aluminium weighing 0.2 g was placed in a Nickel, silver or platinum Cup, pour 5 cmof sodium hydroxide solution with a mass fraction of 20% or 20 cmof water.

A Cup with a lid and heated to dissolve sample. Then wash the lid and the walls of the Cup with water and pour the solution into a beaker with a capacity of 150 cmcontaining 2 mol/DMsolution of sulphuric acid in the quantity required to transfer 0.2 g aluminum sulfate (5.6 cm), to create an acidity of 0.07 mol/DMof 100 cm(3.5 cm) and to neutralize the sodium hydroxide. The acid consumption for neutralization of sodium hydroxide by titration set 5 cmof sodium hydroxide solution 2 mol/DMsolution of sulphuric acid in presence of methyl orange.

The solution was transferred to a glass of acid with the help of plastic sticks, making sure that the solution does not get on the side of the Cup. The contents of the Cup was heated until complete dissolution of the aluminium hydroxide. Then added dropwise a solution of potassium permanganate to obtain laboratoy color. The solution is heated to decolouration, cooled, transferred to a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

Pipetted 5−25 cmof solution, depending on the assumed mass fraction of silicon in a volumetric flask with a capacity of 100 cmand dilute to 50 cm0,07 mol/DMsulfuric acid solution. Then pour 5 cmof molybdate ammonium solution with a mass fraction of 5%, mix and leave to stand for 10 min. then add 25 cm4 mol/DMsulfuric acid solution, washing the throat of the flask, the stirred solution and after 3 min add 5 cmof ascorbic acid. The solution was diluted to the mark with water and mix.

After 20 minutes, measure the optical density of the solution on the photoelectrocolorimeter or spectrophotometer, given that a maximum of light absorption of solutions corresponds to a wavelength of 810 nm. Solution comparison is water.

At the same time spend control experience. To do this in a glass with a capacity of 100 cmplaced 2 mol/DMsolution of sulfuric acid in an amount of 5.6 cmless than for the test solution and gently pour in 5 cmof sodium hydroxide solution. The solution was transferred to volumetric flask with a capacity of 100 cm, is diluted to the mark with water. Select aliquot part of the solution corresponding to aliquote part of test solution in a volumetric flask with a capacity of 100 cm, and the analysis is carried out as described above.

The mass of silicon is determined according to the calibration schedule 1, taking into account the amendment in the reference experiment.

(Modified R

acaccia, Rev. N 3).

3.2. For the determination of silicon in aluminium of high purity is used the method of electrochemical dissolution or extraction method.

(Changed edition, Rev. N 1).

3.2.1. Method with application of electrochemical dissolution.

A sample of aluminum, made in the form of two rods, cleaned by boiling in hydrochloric acid, diluted 1:1 for 10 min. Then washed the rods with water, dried at a temperature of 105−110 °C and weigh after cooling.

In a quartz glass with a capacity of 100−200 cm45 cm is pouredin 2.5 mol/DMnitric acid. The rods reinforce the holders of high-purity aluminium or titanium that are attached to the terminals Later, then the rods are immersed in a glass of acid, include Latr in the network, and dissolve a portion in the range of voltage of 10−20 V for 15 min during this time dissolve about 1 g of aluminum. Allowed the decomposition of the sample with a selenium rectifier, applying the electrodes of the Fisher.

Then Latr turned off, disconnect the rods, washed with water, dried and weighed. From the difference of the masses determine the mass of soluble aluminum. It is necessary that the mass of dissolved aluminum was 1 g, otherwise continue the dissolution. The solution was boiled to remove oxides of nitrogen for 15 min, add a solution of potassium permanganate to obtain a pink color and is heated to bleaching. After cooling, the solution was transferred to volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

Pipetted aliquot part of the solution, corresponding to approximately 0.5 g of aluminum, in a volumetric flask with a capacity of 100 cm. Add missing quantity of a solution of 5 mol/DMnitric acid for complete bonding of the aluminum nitrate and to create acidity, equal to 0.14 mol/DMin the range of 50 cm. To determine the missing quantity of nitric acid, proceed as follows: pipetted 5 cmof the solution in the conical flask, diluted with water, heated to boiling and titrated 0.5 mol/DMsolution of sodium hydroxide to a slightly pink color of phenolphthalein. Counting the total acid content for aliquote part of the solution, which is taken to the definition. Obtained by the titration of the total acid content should be less than that required for the formation of nitrate of aluminum. (For the conversion of 1 g of aluminum nitrate must 22,2 cm5 mol/DMnitric acid).

Counting missing number is 5 mol/DMnitric acid for binding aluminum nitrate and to create acidity of 0.14 mol/DMin the range of 50 cm(for increasing the acidity of the solution at 0.01 mol/DMin the range of 50 cm0.1 cm requires5 mol/lacid solution).

After adding the required amount of nitric acid (the solution volume should be approximately 50 cm) pour 5 cmof molybdate ammonium solution with a mass fraction of 5%, mix and leave for 10 minutes Then add 30 cm4 mol/DMsulfuric acid solution, washing the walls of the throat of the flask, mixed and after 3 min add with stirring 5 cmof a solution of ascorbic acid. The solution was diluted to the mark with water and mix. Measure the optical density of the solution, as stated in claim 3.1.

At the same time spend control experience. To do this in a volumetric flask with a capacity of 100 cmis placed 48 cmof water, 1.4 cm5 mol/DMnitric acid solution, 5 cmof ammonium molybdate with a mass fraction of 5% and analysis was carried out as specified in section 3.1.

A lot of silicon find the calibration schedule 2, given wher

internals control experience.

3.2.2. Extraction method

0.5 g of sample was placed in a platinum, Nickel, silver or Teflon Cup with cover, add 10 cmof sodium hydroxide solution and heated to dissolve sample. After dissolution, the cover is washed with water, the solution slightly cooled, add 1 cmof hydrogen peroxide solution and carefully evaporated to a syrupy condition. After cooling, add 30−40 cmof water and again heated, without boiling, until complete dissolution of salts. The solution was cooled and transferred into a beaker with a capacity of 250 cm, with 20 cm4 mol/DMsulfuric acid; the Cup is washed several times with hot water. The solution is heated to dissolve the salts, dilute with water to 80 cmand cooled.

The solution was transferred to a separatory funnel with a capacity of 250 cmwith a mark at 100 cmand dilute with water to volume of 100 cm, add 5 cmof molybdate ammonium solution with a mass fraction of 10.6%, mix and leave for 10 minutes Then add 20 cmof 8.85 mol/DMsulfuric acid solution, mix and immediately add 5 cmof a solution of ascorbic acid or 5 cmof the solution aminonaphthalene acid, then mix and leave for 30 min.

After 30 min the solution was added 25 cmbutyl alcohol, shaken for 1 min, after the separation of the organic phase is placed in a dry flask containing 20 g of sodium sulfate, from time to time shaking the flask. After 20 minutes, measure the optical density of the organic phase on the spectrophotometer or photoelectrocolorimeter, given that the maximum light absorption of the solutions corresponds to a wavelength of 810 mm.

Solution comparison is butyl alcohol.

Simultaneously with the analysis and under the same conditions, a solution of the reference experiment, but instead of 20 cmusing 13 cm4 mol/DMsolution of sulphuric acid.

A lot of silicon find the calibration schedule 3, taking into account the correction control

LEGO experience.

3.2.1, 3.2.2. (Changed edition, Rev. N 1, 3).

3.3. Construction of calibration graphs

3.3.1. Graph 1

In a volumetric flask with a capacity of 100 cmtaken at 10 cmof the solution of the background and flow of microburette 0; 1; 2; 4; 6; 8; 12 cmstandard solution B, which corresponds to 0; 0,010; 0,020; 0,040; 0,060; 0,080; 0,12 mg silicon.

Dilute the solution to 50 cm0,07 mol/DMsolution of sulphuric acid, poured 5cmof molybdate ammonium solution with a mass fraction of 5% and then received, as indicated in paragraph 3.1. Solution comparison is the solution in which silicon was not added.

According to the obtained values of optical density and known mass of silicon to build a calibration curve 1.

3.3.2. Chart 2

In a volumetric flask with a capacity of 100 cmis placed 25 cmof a solution of aluminum (approximately 0.5 g of aluminum) and poured from microburette 0; 1; 2; 4; 6; 8; 10 cmstandard solution, which corresponds to 0; 0,005; 0,010; 0,020; 0,030; 0,040; 0,050 mg silicon.

Pour the missing amount of 5 mol/DMnitric acid solution, which is calculated as described in section 3.2.

The solution is diluted with water to 50 cm, pour 5 cmof molybdate ammonium solution with a mass fraction of 5% and analysis was carried out as specified in section 3.1.

Solution comparison is the solution in which silicon was not added. According to the obtained values of optical density and known mass of silicon to build the calibration graph 2.

3.3.3. Chart 3

To build a calibration curve in seven separating funnels capacity of 250 cmwith a mark at 100 cm,adding 25 cmof a solution of aluminum. Next, alternately add 1,0; 2,5; 5,0; 7,5; 10,0 and 12,5 cmstandard solution, which corresponds to 0,002; 0,005; 0,010; 0,015; 0,025 0,020 and mg silicon. In the seventh flask solution is not added. The solutions were diluted with water to a volume of 100 cmand then continue the analysis as described in section 3.2.2.

Solution comparison is the solution in which silicon was not added.

According to the obtained values of optical density and known mass of silicon to build the calibration graph.

3.3.1−3.3.3. (Changed edition, Rev. N 1, 3).

4. PROCESSING OF THE RESULTS

4.1. Mass fraction of silicon () in percent is calculated by the formula

,

where is the mass of silicon was found in the calibration graphics mg;

 — the total volume of solution, cm;

 — volume aliquote part of the solution, cm;

the weight of aluminium,

(Changed edition, Rev. N 1).

4.2. Permissible discrepancies in the results of parallel definitions should not exceed the values given in the table.

(Changed edition, Rev. N 1, 3).