GOST 1953.2-79

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  ГОСТ 1953.2-79

GOST 1953.2−79 Bronze tin. Methods for determination of lead (with Amendments No. 1, 2)

GOST 1953.2−79

Group B59

INTERSTATE STANDARD

BRONZE TIN

Methods for determination of lead

Tin bronze.
Methods for the determination of lead

AXTU 1709

Date of introduction 1981−01−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of nonferrous metallurgy of the USSR

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from 10.10.79 N 3899

3. The standard fully complies ST SEV 1530−79

4. REPLACE GOST 1953.2−74

5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

6. Limitation of actions taken by Protocol No. 5−94 of the Interstate Council for standardization, Metrology and certification (ICS 11−12−94)

7. EDITION with Amendments No. 1 and 2, approved in February 1983, August 1990 (IUS 6−83,11−90)


This standard sets the polarographic method for determining lead (from 0.002% to 0.6%), electrogravimetry method for the determination of lead (from 1% to 4%), titrimetric method for determination of lead (from 1% to 30%) and atomic absorption method for the determination of lead (with a mass fraction of lead from 0.002% to 0.02% and more than 0.02% to 12%) in tin bronze according to GOST 5017, GOST GOST 613 and 614.

The standard fully complies ST SEV 1530−79.

(Changed edition, Rev. N 1, 2).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 25086 with the Supplement according to claim 1.1 GOST 1953.1.

(Changed edition, Rev. N 1, 2).

2. POLAROGRAPHIC METHOD for DETERMINING LEAD (from 0.002% to 0.6%)

2.1. The essence of the method

The method is based on preliminary separation of the tin by Stripping in the form of volatile tetrabromide of tin by dissolving the bronze in a mixture of bromine and bromatological acid, the separation of lead from copper coprecipitation of lead with iron hydroxide by ammonia with the subsequent dissolution of the precipitate and determination of lead in polarography AC or DC in a solution of phosphoric acid.

2.2. Apparatus, reagents and solutions

Polarograph AC or DC current and the cell with an external electrode (saturated calomel electrode) and mercury-drip cathode.

Hydrochloric acid according to GOST 3118, diluted 1:1 and 1:10.

The acid chloride.

Bromatologia acid according to GOST 2062.

Bromine according to GOST 4109.

A mixture of bromine for the dissolution, freshly made: nine volumes bromatological acid is mixed with one volume of bromine.

Ammonia water according to GOST 3760, diluted 1:50.

Orthophosphoric acid according to GOST 6552, diluted 1:3 and 1 mol/DMsolution.

Nitric acid according to GOST 4461, diluted 1:1.

Iron chloride according to GOST 4147, 50 g/lin hydrochloric acid 1:10.

Mercury GOST 4658 stamps r0, drained.

Lead at GOST brand 3778 S0.

Solutions of lead. Solution A, prepared as follows: 0.25 g of metallic lead is dissolved by heating in 30 cmof nitric acid is removed by boiling the oxides of nitrogen, cooled, poured 50 cmof water, transferred to a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.001 g of lead.

Solution B is prepared as follows: 10 cmof solution A is placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.0001 g of lead.

Nitrogen gas according to GOST 9293.

(Changed edition, Rev. N 2).

2.3. Analysis

The sample of bronze with a weight of 1 g when the mass fraction of lead from 0.002% to 0.25% and 0.5 g for the mass concentration of lead in excess of 0.25% placed in a beaker with a capacity of 250 cm, cover with a watch glass and dissolved in 20 cmbromine mixture. In case of incomplete dissolution of the alloy into the glass drop by drop add bromine.

Upon completion of the dissolution solution was poured to 20 cmof perchloric acid and evaporated the solution at a moderate heat to release thick white smoke and lightening solution. The solution was cooled, rinse walls of beaker and watch glass with water and repeat the evaporation until the appearance of dense white smoke of perchloric acid. Cool the beaker, rinse walls of beaker with a little water and heated to dissolve the salts. Dilute the solution with water to 150 cm, add 1 cmof solution of ferric chloride, the mixture was heated to 60−70 °C and poured ammonia before the transfer of all of the soluble copper in the dark blue ammonia complex.

Solution to precipitate the hydroxide is kept in a warm place for 20 min to coagulate the precipitate, and then filtered through a paper filter of medium density. The glass and the filter cake washed with ammonia solution, diluted 1:50. The funnel with the precipitate was placed on glass, which made the deposition, the precipitate was dissolved in 20 cmof hydrochloric acid and the filter washed with 50 cmof hot water. The resulting solution was diluted with water to 150 cmand repeat the precipitation of the hydroxide by ammonia, their separation and dissolution, as described above, two more times. The filter cake is dissolved in 5 cmof perchloric acid, rinse the filter with 50 cmof hot water and the resulting solution is evaporated until a white smoke of perchloric acid. Add 15 cmof water, the solution transferred to a volumetric flask with a capacity of 50 cm, 14 cm pouredphosphoric acid, diluted 1:3, made up to the mark with water and mix.

Aliquot part of the obtained solution volume of 10 cmis transferred into a polarographic cell, pre-washed in 1 mol/DMsolution of phosphoric acid. Through the cell, pass nitrogen for 5−7 min, stop stirring and remove the cathode polarogram in the voltage range from minus 0.25 to minus 0.7 V. Recovery of lead is recorded about minus 0.5 V. the Sensitivity of polarography choose so that the peak height was not less than 20−25 mm.

Lead find by the method of standard additions. Aliquot part of the standard solution B (0.2 to 0.6 cm) was added into the solution, stirred the solution for 2 min and polarografic the same as in the case of the analyzed solution. The amount of standard addition is selected so that the height of the peak of lead increased by 2−3 times compared to the peak height of lead in solution. At the same time conducting follow-up experience with all reagents as described above.

(Changed edition, Rev. N 1).

2.4. Processing of the results

2.4.1. Mass fraction of lead (a) percentage calculated by the formula

,

where is the peak height of lead in a control experiment, mm.

the peak height of lead in the sample solution, mm;

the peak height of lead in the sample solution after the introduction of standard additives, mm;

 — the volume of standard solution added into the solution, cm;

 — the concentration of a standard solution of lead, g/cm;

the weight of bronze,

2.4.2. Discrepancies in the results of parallel definitions should not exceed the values of permissible differences (the rate of convergence for 3) specified in table.1.

Table 1

(Changed edition, Rev. N 2).

2.4.3. Discrepancies in the results analysis, obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values specified in table.1.

2.4.4. Control of accuracy of analysis results is carried out according to State standard samples of tin bronzes, re-approved by GOST 8.315, or by additives or by comparison of the results obtained by atomic absorption method, in accordance with GOST 25086.

2.4.3, 2.4.4. (Added, Rev. N 2).

3. TITRIMETRIC CHELATOMETRIC METHOD for the DETERMINATION of LEAD (from 1.0% to 30%)

3.1.The essence of the method

The method is based on titration of lead at pH of 5.4−6.0 mm solution of Trilon B in the presence kylinalove orange as indicator after its separation in the form of sulphate of lead, and dissolve in ammonium acetate.

(Changed edition, Rev. N 1).

3.2. Reagents and solutions

Sulfuric acid according to GOST 4204, diluted 1:1 and 1:50.

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

Hydrochloric acid according to GOST 3118.

A mixture of nitric and hydrochloric acids; prepared as follows: one volume of nitric acid mixed with three volumes of hydrochloric acid.

Rectified ethyl alcohol according to GOST 18300.

Potassium ferrocyanide according to GOST 4207, a solution of 30 g/DM.

Ammonium acetate according to GOST 3117, a solution of 150 g/DM(1 DMof the solution is added 3 cmof hydrochloric acid).

Lead metal according to GOST 3778 brands S0.

Indicator kylinalove orange, with a well-powdered mixture with sodium chloride in a ratio of 1:100.

Sodium chloride according to GOST 4233.

Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid, 2-water (Trilon B) according to GOST 10652, solution 0,025 mol/DM, prepare fiksanala or as follows: 9,305 g Trilon B dissolved in 500 cmof water when heated, transferred to a volumetric flask with a capacity of 1 DMand topped to the mark with water.

The installation of the mass concentration of the solution Trilon B.

0.1 g of lead dissolved in 15 cm.of nitric acid diluted 1:1, poured 20 cmof sulphuric acid diluted 1:1, and is evaporated until a white smoke of sulfuric acid. The solution was cooled, rinse walls of beaker with water and repeat the evaporation until a white smoke of sulfuric acid. After cooling, to the residue poured 150 cmof water, heated to dissolve the salts, and cooled, then poured in 40 cmethanol and left for 4 h. Then do as stated in claim 3.3.

The mass concentration of the solution Trilon B (), expressed in grams of lead per 1 cmof a solution, calculated by the formula

,

where  — suspension of lead, g;

 — volume of solution Trilon B, spent on titration, sm.

(Changed edition, Rev. N 2).

3.3. Analysis

The sample of bronze with a weight of 1 g when the mass fraction of lead from 1% to 10% or 0.2 g when the mass fraction of lead from 10% to 30% were placed in a glass with a capacity of 300 cm, cover with a watch glass and dissolved in 15 cmof the mixture of acids when heated. After dissolution of the alloy glass is then rinsed with water, poured 20 cmof sulphuric acid diluted 1:1, and is evaporated until a white smoke of sulfuric acid. The solution was cooled, the side of the Cup then rinsed with water and again evaporated until a white smoke of sulfuric acid. The residue is cooled, poured 150 cmof water, heated to dissolve the salts, and cooled. Then pour 40 cmethanol and left for 4 h. the Separated precipitate of lead sulphate filtered off on a tight filter with filtrowanie ground; the glass is rinsed with sulfuric acid, diluted 1:50, and the precipitate washed with the same acid until complete removal of copper in the washing water (test with potassium ferrocyanide), and then 2−3 times with water. The filter with precipitate was placed in a beaker, in which was conducted the deposition, pour 50 cmof a solution of acetate of ammonia, heated to boiling and boil 2 min. Then diluted with water to a volume of 80 cm, and the solution is cooled.

The resulting solution is added at the tip of a spatula mix kylinalove orange with sodium chloride and slowly titrated with a solution of Trilon B to a transition of a purple color to yellow.

(Changed edition, Rev. N 1, 2)

.

3.4. Processing of the results

3.4.1. Mass fraction of lead (a) percentage calculated by the formula

,

where  — volume of solution Trilon B, used for titration, cm;

 — mass concentration of the solution Trilon B on lead, g/cm;

 — weight of sample, g.

3.4.2. Discrepancies in the results of parallel definitions should not exceed the values of permissible differences (the rate of convergence for 3) specified in table.1.

(Changed edition, Rev. N 2).

3.4.3. Discrepancies in the results analysis, obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values specified in table.1.

3.4.4. Control of accuracy of analysis results is carried out according to State standard samples of tin bronzes, re-approved by GOST 8.315, or a comparison of the results obtained by atomic absorption method, in accordance with GOST 25086.

3.4.3, 3.4.4. (Added, Rev. N 2).

4. ATOMIC ABSORPTION METHOD for the DETERMINATION of LEAD (from 0.002% to 0.02%)

4.1.The essence of the method

The method is based on measurement of light absorption by atoms of lead, formed by the introduction of the analyzed solution in the flame acetylene-air, after pre-allocation of lead with precipitation with ferric hydroxide.

4.2. Apparatus, reagents and solutions

Atomic absorption spectrometer with a radiation source for lead.

Nitric acid according to GOST 4461, diluted 1:1.

Hydrochloric acid according to GOST 3118 and diluted 1:1, 1:3 and 2M solution.

Hydrofluoric acid according to GOST 10484.

The acid chloride.

Bromatologia acid according to GOST 2062.

Bromine according to GOST 4109.

Mix to dissolve, freshly prepared; prepared as follows: 9 parts bromatological acid mixed with one part of bromine.

Ammonia water according to GOST 3760 and diluted 1:19.

Hydrogen peroxide (perhydrol) according to GOST 10929.

Iron chloride, solution 15 g/lin hydrochloric acid, diluted 1:3.

Aluminum metal with a mass fraction of lead is lower than 0.001%.

Aluminium chloride solution 50 g/l; prepared as follows: 5 g of aluminium is dissolved in 150 cmof hydrochloric acid diluted 1:1 with the addition of a few drops of hydrogen peroxide. The solution was evaporated until beginning crystallization of aluminum chloride, cooled, transferred to a volumetric flask with a capacity of 100 cmand top up with water to the mark.

Lead according to GOST 3778 with a mass fraction of lead not less than 99.9%.

Standard solutions of lead.

Solution A, prepared as follows: 0.5 g of lead is dissolved by heating in 20 cmof nitric acid, diluted 1:1, the solution was cooled, transferred to a measuring flask with volume capacity of 1000 cmand top up with water to the mark.

1 cmof the solution contains 0.0005 g of lead.

Solution B is prepared as follows: 20 cmsolution And placed in a volumetric flask with a capacity of 100 cm, add 10 cmof 2 mol/DMhydrochloric acid solution and add water to the mark.

1 cmof a solution contains 0.0001 g of lead.

4.3. Analysis

4.3.1. For bronzes, with a mass fraction of tin, silicon and aluminum, up to 0.05%

The weight of bronze weighing 2 g were placed in a glass with a capacity of 250 cmand dissolved by heating in 20 cmof nitric acid, diluted 1:1. Nitrogen oxides are removed by boiling and the solution diluted with water to a volume of 150 cm. Add 5 cmof a solution of ferric chloride (bronze containing iron as an alloying component, should not be added to a solution of ferric chloride), the solution is heated to a temperature of 80−90 °C and ammonia is added to complete the transition of copper and Nickel in ammoniacal systems. The precipitate of hydroxide is allowed to stand for 10 min at 60 °C, filtered on a medium density filter and washed with hot ammonia solution, diluted 1:19 for the removal of copper and Nickel, and then 3 times with hot water.

The deployed filter washed with hot water into a glass, which conducted the deposition, the filter is washed with 10 cmof hot hydrochloric acid solution, diluted 1:1 and then with water. The washed filter is discarded and the solution was evaporated to a volume of 5 cm. The solution was cooled, added to 10 cmof water, transferred to a volumetric flask with a capacity of 25 cmand top up with water to the mark.

Measure the atomic absorption of lead in the flame of acetylene-air at a wavelength is 283.3 nm parallel to the calibration solutions.

4.3.2. For bronzes, with a mass fraction of tin in excess of 0.05%.

The weight of bronze weighing 2 g were placed in a glass with a capacity of 250 cm, adding 25 cmof the mixture to dissolve and gently heated until complete dissolution. Then add 10 cmof perchloric acid and evaporated to a volume of 4 cm. The residue was cooled, added to 30 cmof water and heated to dissolve the salts. The solution is diluted with water to a volume of 150 cm, add 5 cmof a solution of ferric chloride, heated to a temperature of 80−90 °C, ammonia is added to complete the transition of copper ammonia complex and further analysis are as indicated in claim 4.3.1.

4.3.3. For bronzes, with a mass fraction of silicon in excess of 0.05%

The weight of bronze weighing 2 g was placed in a platinum Cup and dissolved by heating in 20 cmof nitric acid, diluted 1:1, and 2 cmhydrofluoric acid. Then add 10 cmof perchloric acid and heated until the appearance of dense white fumes. The residue was cooled, added to 30 cmof water and heated to dissolve the salts. The solution was transferred to a beaker with a capacity of 250 cm, is diluted with water to a volume of 150 cm, add 5 cmof a solution of ferric chloride, heated to a temperature of 80−90 °C, ammonia is added to complete the transition of copper ammonia complex and further analysis are as indicated in claim 4.3.1.

4.3.4. For bronzes containing aluminum as a component

The weight of bronze weighing 2 g were placed in a glass with a capacity of 250 cmand dissolved by heating in 20 cmof a solution of nitric acid, diluted 1:1, with the addition of a few drops of hydrochloric acid. Nitrogen oxides are removed by boiling and the solution diluted with water to a volume of 150 cm. The solution is heated to a temperature of 80−90 °C, ammonia is added to complete the transition of copper ammonia complex and further analysis are as indicated in claim 4.3.1.

4.3.5. Construction of calibration graphs

4.3.5.1. For bronzes that do not contain aluminium as a component

In six of the seven volumetric flasks with a capacity of 100 cmis placed 1,0; 2,5; 5,0; 10,0; 15,0 and 20.0 cmstandard solution B lead. To each flask add 10 cmof 2 mol/DMhydrochloric acid solution and add water to the mark.

Measure the atomic absorption of lead as specified in claim 4.3.1. According to the obtained results build a calibration curve.

4.3.5.2. For bronzes containing aluminum as a component

In seven volumetric flasks with a capacity of 50 cmis placed, depending on the aluminum content in the sample, from 2 to 10 cmof a solution of aluminum chloride and in six of them add 0,5; 1,25; 2,5; 5,0; 7,5 and 10,0 cmstandard solution B lead, 5 cmof 2 mol/DMhydrochloric acid solution and add water to the mark.

Measure the atomic absorption of lead as specified in claim 4.3.1. According to the obtained results build a calibration curve.

4.4. Processing of the results

4.4.1. Mass fraction of lead (a) percentage calculated by the formula

,

where is the concentration of lead was found in the calibration schedule, g/cm;

 — the volume of the final sample solution, cm;

 — the weight of the portion,

4.4, 4.4.1. (Changed edition, Rev. N 1).

4.4.2. Discrepancies in the results of parallel definitions should not exceed the values of permissible differences (the rate of convergence for 3) specified in table.1.

(Changed edition, Rev. N 2).

4.4.3. Discrepancies in the results analysis, obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values specified in table.1.

4.4.4. Control of accuracy of analysis results is carried out according to State standard samples of tin bronzes, re-approved by GOST 8.315, or by additives or by comparison of the results obtained of the polarographic method, in accordance with GOST 25086.

4.4.3, 4.4.4. (Added, Rev. N 2).

5. ATOMIC ABSORPTION METHOD for the DETERMINATION of LEAD (from 0.02% to 12%)

5.1.The essence of the method

The method is based on measuring the absorption of light by atoms of lead, formed by the introduction of the analyzed solution in the flame acetylene-air.

5.2. Apparatus, reagents and solutions

Atomic absorption spectrometer with a radiation source for lead.

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

Hydrochloric acid according to GOST 3118, 2 mol/land 1 mol/DMsolutions.

The mixture of acids to dissolve; prepared as follows: the amount of nitric acid mixed with three volumes of hydrochloric acid.

Hydrofluoric acid according to GOST 10484.

The acid chloride.

Lead according to GOST 3778 with a mass fraction of lead not less than 99.9%.

Standard solutions of lead.

Solution A, prepared as follows: 0.5 g of lead is dissolved by heating in 20 cmof nitric acid, diluted 1:1, the solution was cooled, transferred to a measuring flask with volume capacity of 1000 cmand top up with water to the mark.

1 cmof the solution contains 0.0005 g of lead.

Solution B is prepared as follows: 20 cmsolution And transferred to a volumetric flask with a capacity of 100 cm, add 10 cmof 2 mol/DMhydrochloric acid solution and add water to the mark.

1 cmof a solution contains 0.0001 g of lead.

5.3. Analysis

5.3.1. For bronzes, with a mass fraction of tin and silicon up to 0.05%

A portion of the bronze mass, given in table.2, is placed in a beaker with a capacity of 250 cmand dissolved by heating in 10 cmof nitric acid, diluted 1:1. The solution was cooled, transferred to a volumetric flask with a capacity of 100 cmand top up with water to the mark.

Table 2

When the mass fraction of lead more than 1% 10 cmof the solution transferred to an appropriate volumetric flask (see table 2) add 2 mol/DMhydrochloric acid solution (see table.2) and top up with water to the mark.

Measure the atomic absorption of lead in the flame of acetylene-air at a wavelength is 283.3 nm parallel to the calibration solutions.

5.3.2. For bronzes, with a mass fraction of tin in excess of 0.05%.

A portion of the bronze mass, given in table.2, is placed in a beaker with a capacity of 250 cmand dissolved by heating in 10 cmof a mixture of acids. The solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, rinse walls of beaker 1 mol/DMsolution of hydrochloric acid and topped up to the mark with the same acid. When the mass fraction of lead more than 1% 10 cmof the solution transferred to an appropriate volumetric flask (see table 2) and topped to the mark of 1 mol/DMhydrochloric acid solution.

Measure the atomic absorption of lead, as specified in clause 5.3.1.

5.3.3. For bronzes, with a mass fraction of silicon in excess of 0.05%

A portion of the bronze mass, given in table.2, is placed in a platinum Cup and dissolved by heating in 10 cmof nitric acid, diluted 1:1, and 2 cmhydrofluoric acid. Then add 10 cmof perchloric acid and heated until the appearance of dense white fumes. The residue is dissolved under heating in water.

The solution was cooled, transferred to a volumetric flask with a capacity of 100 cmand top up with water to the mark. When the mass fraction of lead more than 1% 10 cmof the solution transferred to an appropriate volumetric flask (see table 2) add 2 mol/DMhydrochloric acid solution (see table.2) and top up with water to the mark.

Measure the atomic absorption of lead, as specified in clause 5.3.1.

5.3.4. Construction of calibration curve

In eleven of the twelve volumetric flasks with a capacity of 100 cmis placed 1,0; 2,5; 5,0 and 10,0 cmstandard solution B, and 2,0; 3,0; 4,0; 6,0; 8,0; 10,0 and 12.0 cmstandard solution And lead. To all flasks add 10 cmof 2 mol/DMhydrochloric acid solution and add water to the mark.

Measure the atomic absorption of lead, as specified in clause 5.3.1. According to the obtained results build a calibration curve.

5.4. Processing of the results

5.4.1. Mass fraction of lead (a) percentage calculated by the formula

,

where is the concentration of lead was found in the calibration schedule, g/cm;

 — the volume of the final sample solution, cm;

 — the weight of the portion contained in the final volume of the sample solution,

5.1−5.4.1. (Changed edition, Rev. N 1).

5.4.2. Discrepancies in the results of parallel definitions should not exceed the values of permissible differences (the rate of convergence for 3) specified in table.1.

(Changed edition, Rev. N 2).

5.4.3. Discrepancies in the results analysis, obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values specified in table.1.

5.4.4. Control of accuracy of analysis results is carried out as specified in clause 4.4.4.

5.4.5. Atomic absorption method is used in case of disagreement in assessing the quality of tin bronzes.

5.4.3−5.4.5. (Added, Rev. N 2).

6. ELECTROGRAVIMETRY METHOD FOR THE DETERMINATION OF LEAD

6.1. The essence of the method

The method is based on the release of lead by electrolysis after prior separation of tin in the form of metalbands acid and weighing the separated precipitate of lead dioxide on the anode.

6.2. Equipment, reagents

Electrolysis installation DC.

Platinum mesh electrodes according to GOST 6563.

Nitric acid according to GOST 4461, diluted 1:1 and 1:100.

Ammonium nitrate according to GOST 22867, a solution of 300 g/DM.

6.3. Analysis

A sample weighing 0.5 g were placed in a glass with a capacity of 250 cm, add 15 cmof nitric acid (1:1), cover with a watch glass and dissolved under heating. After dissolution of the alloy glass is removed, rinsed with water and the solution is evaporated to 5−10 cm. To the residue add 50 cmof hot water, 10 cmof ammonium nitrate solution and allowed to stand in a warm place for 1 hour

Metalbands acid precipitate is filtered off on a tight filter with filtrowanie mass, collecting the filtrate in a beaker with a capacity of 250−300 cm. The filter residue is washed with hot nitric acid (1:10) to complete removal of copper and lead.

Selected sediment metalbands acid used in the gravimetric method for determination of tin GOST 1953.3. The filtrate is evaporated to 150 cm, immersed in a solution of suspended anode and a cathode and conducting electrolysis with a current of 1.5−2 And while stirring the solution. The glass electrolyte must be covered by the two halves of the hour glass or plastic plate with holes for electrodes and stirrer.

After 30 min from the start of the electrolysis is removed or the glass plate, rinsed with water, and continue the electrolysis for 15 min. If after that svezhemorozhenoj in the solution part of the anode is not allocated sediment, electrolysis is considered complete. Without turning off the current, remove the electrodes from the electrolyte, rinse the electrodes, collecting the rinse water in the beaker with the electrolyte, shut off the current, remove the anode and the precipitate of dioxide of lead, immerse it in a glass of water, and then in a glass with alcohol, dried it at 160−170 °C to constant weight, cooled and weighed.

One serving of alcohol (200 cm) can be used for washing of the electrodes 20.

6.4. Processing of the results

6.4.1. Mass fraction of lead (a) percentage calculated by the formula

,

where  — mass of anode, g;

 — the mass of the anode from the separated precipitate of dioxide of lead, g;

0,8662 — the conversion factor of lead dioxide on a lead;

 — the weight of the portion,

6.4.2. Discrepancies in the results of parallel definitions should not exceed the values of permissible differences (the rate of convergence for 3) specified in table.1.

6.4.3. Discrepancies in the results analysis, obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values specified in table.1.

6.4.4. Control of accuracy of analysis results is carried out according to State standard samples of tin bronzes, re-approved by GOST 8.315, or by comparing the results obtained with titrimetric or atomic absorption methods, in accordance with GOST 25086.

Sec. 6. (Added, Rev. N 2).