GOST 12697.5-77

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  ГОСТ 12697.5-77

GOST 12697.5−77 Aluminum. Method of determining chromium (with Amendments No. 1, 2, 3)

GOST 12697.5−77

Group B59

INTERSTATE STANDARD

ALUMINIUM

Method for the determination of chromium

Aluminium. Method for determination of chromium

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 12701−67 in part of sec. 2

EDITION with Amendments No. 1, 2, 3, approved in November 1981, November 1985, may 1988 (ICS 1−82, 2−86, 8−88).


This standard sets the photometric method for the determination of chromium in aluminum (with a mass fraction of chromium from 0,0002 to 0,1 per cent).

The method is based on the oxidation of chromium by permanganate neccersarily potassium or ammonium in the presence of the catalyst to the hexavalent state and education in an acidic medium soluble compounds purple color difenilcarbazida.

The method provides two options for the analysis without extraction and with extraction of chromium.

Colored solution photometered in nm.

(Changed edition, Rev. N 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**.

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

Sulfuric acid GOST 4204−77, solutions 2 and 4 mol/DM.

Orthophosphoric acid according to GOST 6552−80, diluted 1:10.

Manganese sulfate according to GOST 435−77, a solution with a mass fraction of 0.01%.

Silver nitrate according to GOST 1277−75, a solution with a mass fraction of 1%.

Sodium hydroxide according to GOST 4328−77, a solution with a mass fraction of 20%. Store in a plastic container.

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

Sodium atomistically according to GOST 4197−74, a solution of 0.1 g/DM.

Potassium permanganate according to GOST 20490−75, solution 0,02 mol/DM.

Ammonium neccersarily according to GOST 20478−75, a freshly prepared solution with a mass fraction of 10%.

Aluminum brand A995 according to GOST 11069−2001.

Solution of aluminum 20 and 25 g/DM; prepared as follows: 2.0 or 2.5 g of aluminium is dissolved in 50 cmof sodium hydroxide when heated, after cooling, transfer the solution into a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix. The solution was stored in a plastic container.

Urea according to GOST 6691−77.

Acetone according to GOST 2603−79. If necessary, acetone is subjected to a preliminary distillation at 56 °C.

Diphenylcarbazide by ND, freshly prepared solutions with a mass fraction of 0.1 and 0.25% in acetone. The solution is painted in brown color, for the analysis. In the case of the analysis with the extraction solution used difenilcarbazida cooled to 5−10 °C.

Potassium dichromate according to GOST 4220−75.

Hydrochloric acid by the GOST 3118−77, solutions of 0.5 and 6 mol/DM.

Nitric acid GOST 4461−77.

Mix acids in a glass with a capacity of 1000 cmis placed 200 cmof concentrated hydrochloric acid, 200 cmof concentrated nitric acid and 400 cmof water. With constant stirring and cooling added to 120 cmof concentrated sulfuric acid. After cooling, the mixture is transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

Hydrofluoric acid according to GOST 10484−78.

Exocervical ammonium [(NH)Ce (NO)], solution 0,02 mol/lfor cerium and 1 mol/lin sulfuric acid.

Of 2.19 g of exocervical ammonium dissolved in a little water and add 25 cm4 mol/DMsolution of sulphuric acid. The solution was transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Methyl isobutyl ketone (MIBK) clean as follows: in a separating funnel with a capacity of 1000 cmwas placed 250 cmMIBK, previously cooled to 5−10 °C, add 250 cmof 0.5 mol/DMof hydrochloric acid of the same temperature, gently shaken for 1 min and left until separation of the phases. Then the aqueous phase is drained and discarded. Cleaned MIBK retain in the vessel with a glass stopper.

The reagent used chilled to 5−10 °C.

Nickel chloride according to GOST 4038−79, a solution with a mass fraction of 2%.

Solutions of chromium standard.

Solution A, prepared as follows: 0,1414 g pre-dried at 150 °C of potassium dichromate dissolved in water, transferred to a volumetric flask with a capacity of 500 cm, is diluted to the mark with water and mix.

1 cmof solution A contains 0.1 mg of chromium (Cr).

Solution B is prepared before use as follows: pipetted 10 cmof solution A in a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.002 mg chromium (Cr).

Solution; prepared before use as follows: pipetted 50 cmof solution B in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.001 mg of chromium.

(Changed edition, Rev. N 1, 3).

3. ANALYSIS

Analysis without extraction

3.1. Weighed aluminium weighing 0.25 g were placed in a glass with a capacity of 100 cm, pour 5 cmof sodium hydroxide solution, cover with a watch glass and heated to dissolve sample. After cooling, wash the glass and walls of glass with water and poured 4 mol/DMsolution of sulphuric acid in the quantity required to transfer 0.25 g of aluminum sulfate (3.5 cm) to create acidity 0.1 mol/DMin the range of 50 cm(1.3 cm) and to neutralize the sodium hydroxide. The acid consumption for neutralization of sodium hydroxide by titration set 5 cmof sodium hydroxide solution 4 mol/DMsolution of sulphuric acid in presence of methyl orange. The contents of the Cup was heated until complete dissolution of the aluminium hydroxide.

Depending on the mass fraction of chromium is carried out to determine from the entire sample or by translating the solution in a volumetric flask with a capacity of 50 cm. In the latter case, for the analysis of selected aliquot part of the solution 5−10 cmand dilute the solution to 25 cmof 0.25 mol/DMsulfuric acid solution.

Then chromium is oxidized with potassium permanganate or ammonium persulfate in the presence of silver nitrate.

The oxidation of chromium with potassium permanganate, add it dropwise until the appearance of pink coloring and heat the solution, without boiling for 15 minutes If during heating the pink color disappears, then add dropwise a solution of potassium permanganate prior to its occurrence.

The oxidation of chromium with ammonium persulfate to the solution add 2 drops of a solution of manganese sulfate, 1 cmof solution azotistykh silver and heat the solution to boiling. In a glass put a few beads for a uniform boiling point of the solution. Add 5 cmof ammonium persulfate, stirring the solution, cover with a glass watch glass and boil the solution on a sand bath for 10 min to destroy the excess of ammonium persulfate. You should be pink colour manganese acid, which is a sign of complete oxidation of chromium.

After oxidation of chromium in one way or another to remove excess manganese acid added to the hot solution dropwise a solution of sodium attestatio to the bleaching solution. To remove excess sodium attestatio you can add 0.5 g of urea.

After cooling, the solution was transferred to volumetric flask with a capacity of 50 cm, add 3 cmof phosphoric acid, 3 cmdiphenylcarbazide solution with a mass fraction of 0.25%, made up to the mark with water and mix. After 10 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 546 nm. When the ratio of vanadium to chromium of no more than 10:1 can be done in 3 min.

Solution comparison is water.

At the same time spend control experience. To do this in a glass with a capacity of 100 cmplaced 4 mol/DMsolution of sulfuric acid in an amount of 3.5 cmless than for the test solution and gently pour in 5 cmof sodium hydroxide solution and analyze as described in section 3.1.1.

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

The analysis is not allowed to wash used dishes

chrome mix.

3.2. Construction of calibration curve

In glasses with a capacity of 100 cmis placed 10 cmsolution aluminum concentration of 25 g/DM, poured from microburette 0; 1; 2; 3; 4; 6; 8; 10 cmof solution B, which corresponds to 0; 0,002; 0,004; 0,008; 0,012; 0,016; 0,020; 0,025 mcg, add the required amount of 4 mol/DMsulphuric acid, heated to dissolve the aluminium hydroxide, cooled and added 3 cmof phosphoric acid, diluted 1:10, spend analysis as indicated in paragraph 3.1.

Solution comparison is the solution in which the chromium was added. According to the obtained values of optical density and known mass of chromium to build the calibration graph.

3.1, 3.2. (Changed edition, Rev. N 1, 3).

3.3. Analysis with the extraction

3.3.1. 1 g sample is dissolved in 50 cmof the mixture of acids, adding it in small portions in a beaker with a capacity of 250 cm, covered with a watch glass.

Upon dissolution of high purity aluminum to accelerate the dissolution before addition of the mixture of acids in a glass put 1 cmof solution of chloride Nickel.

After termination of the reaction the hour glass and the side of the Cup washed with a small amount of water, then the solution is evaporated until the appearance of fumes of sulphuric anhydride and heating was continued for another 10 min. the Solution was cooled, added 40−60 cmof water and heated to dissolve the salts. The solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

If from the solution precipitate of silicic acid, the solution was filtered through a filter medium density, the glass and the precipitate washed several times with hot water. The filter with precipitate was placed in a platinum crucible, dried, incinerated filter with the precipitate was then calcined at 1000 °C for 20 min.

After cooling in the crucible, add two drops of sulfuric acid, 2cmof nitric acid, 5 cmof a solution of hydrofluoric acid and evaporated to dryness. After cooling, the contents of the crucible are dissolved in a small amount of hot water with a few drops of 4 mol/DMsolution of sulphuric acid. The solution was combined with the main filtrate and evaporated to a volume of 50−60 cm, then cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Aliquot part of the sample solution and amount of solution aluminum concentration of 20 g/DMselected according to table.1 and placed in a beaker with a capacity of 100 cmwith the mark at 30 cm.

Table 1

To the solution was added 2.0 cmhexanenitrile solution of ammonia and dilute with water to 30 cm. After mixing the solution, cover the watch glass and heated on a boiling water bath for 25 minutes while maintaining the solution volume by adding water. The solution was then cooled to 5−10 °C.

The solution was transferred to a separatory funnel with a capacity of 100 cmwith the mark at 45 cm, is washed with a glass of water at a temperature of 5−10 °C. the Volume of the solution and top up with water to the mark. Then add in the funnel 4.5 cm6 mol/DMhydrochloric acid solution, the solution is mixed, add 25 cmMIBK and shaken for 1 min. After separation the aqueous phase is transferred into another separatory funnel with a capacity of 100 cm, adding 25 cmMIBK and re-shake 1 min. After the separation of the aqueous phase is discarded and organic phase are combined in the first separating funnel. Allow the grout to settle and the aqueous phase discarded. To the organic phase add 25 cmof 0.5 mol/DMhydrochloric acid solution, shake for 5 s and after separation the aqueous phase is discarded.

When the mass fraction of chromium from of 0.0002 to 0.005% produce the Stripping water by adding one times 10 cmand twice 5 cmof water and shaking each time for 30 s. the Aqueous phase is collected in a volumetric flask with a capacity of 25 cm.

When the mass fraction of chromium from 0.005 to 0.1% produce Stripping of chromium from the organic phase with water, three times adding 15 cmand shaking for 30 s. the Aqueous phase is collected in a volumetric flask with a capacity of 50 cm.

In a volumetric flask with a capacity of 25 cm1.3 cm adding2 mol/DMsulfuric acid solution and after stirring 0.5 cmdiphenylcarbazide solution with a mass fraction of 1% in a volumetric flask with a capacity of 50 cm, add 2.5 cmof 2 mol/DMsulfuric acid solution and after stirring 1 cmdiphenylcarbazide solution with a mass fraction of 1%. The solution in the flask topped up to the mark with water and mix.

After 10 min, add difenilcarbazida 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 546 nm.

Solution comparison is water.

The solution in the reference experiment is prepared as a solution, not containing chromium when you build a calibration curve.

The analysis is not allowed to wash used dishes

have chrome mixture.

3.3.2. To construct the calibration curve for the mass concentration of chromium from of 0.0002 to 0.005% in glasses with a capacity of 100 cmwith the mark on the level of 30 cmplaced at 10 cmof solution aluminum concentration of 20 g/DM, poured from microburette 0; 0,5; 1,0; 2,5; 5,0; 10 cmsolution that fits 0; 0,0005; 0,001; 0,0025; 0,005; 0,10 mg chromium.

To construct the calibration curve for the mass concentration of chromium from 0.005 to 0.1% in glasses with a capacity of 100 cmwith the mark on the level of 30 cmplaced at 10 cmof solution aluminum concentration of 20 g/DM, poured from microburette 0; 0,5; 1,0; 2,0; 2,5; 3,0 cmof solution B, which corresponds to 0; 0,01; 0,02; 0,04; 0,05; 0,06 mg chromium.

The solutions in the beakers add 2 cmof a solution of hexanenitrile ammonium, dilute with water to 30 cmand then do as stated in claim 3.3.1.

Solution comparison is the solution in which the chromium was added.

According to the obtained values of optical density and known mass of the calibration chromium build g

Rafik.

3.3.1−3.3.2. (Changed edition, Rev. N 1, 3).

4. PROCESSING OF THE RESULTS

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

,

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

 — the total volume of solution, cm;

 — volume aliquote part of the solution, cm;

the weight of aluminium,

4.2. Permissible discrepancies in the results of parallel definitions should not exceed the values given in table.2.

Table 2

(Changed edition, Rev. N 1, 3).