GOST 1652.8-77

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  ГОСТ 1652.8-77

GOST 1652.8−77 Alloys copper-zinc. Methods for determination of arsenic (with Amendments No. 1, 2, 3)

GOST 1652.8−77

Group B59

STATE STANDARD OF THE USSR

ALLOYS COPPER-ZINC

Methods for determination of arsenic

Copper-zinc alloys.
Methods for the determination of arsenic

AXTU 1709

Date of introduction 1978−07−01

INFORMATION DATA

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

DEVELOPERS

Y. F. Chuvakin, M. B. Taubkin, A. A. Nemodruk, N. In. Egiazarov (supervisor), I. A. Vorobyev

2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 27.04.77 N 1062

3. REPLACE GOST 1652.8−71

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Resolution of the state standard from 28.12.92 N 1525 removed the limitation of the validity period

6. REPRINT (July 1997) with Amendments No. 1, 2, 3, approved in October 1981, November 1988, December 1993 (IUS 12−81, 2−88, 3−93)


This standard specifies the extraction-photometric method for the determination of arsenic (in mass fraction of arsenic from 0.001 to 0.1%), a photometric method for the determination of arsenic (if arsenic mass fraction of from 0.005 to 0.2%), amperometric method for the determination of arsenic (if arsenic mass fraction of from 0.01 to 0.2%) in copper-zinc alloys according to GOST 15527, GOST and GOST 17711 1020.

(Changed edition, Rev. N 2, 3).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 25086 with the Supplement according to claim 1.1 GOST 1652.1.

(Changed edition, Rev. N 2).

2. EXTRACTION-PHOTOMETRIC METHOD FOR THE DETERMINATION OF ARSENIC

2.1. The essence of the method

The method is based on formation of yellow michalopolous complex with subsequent restoration of its sulphate with hydrazine in acidic solution to michalopolous blue and measuring optical density of colored solution.

Arsenic from the basic components of the alloys are pre-separated by coprecipitation with ferric hydroxide and subsequent extraction in the form of iodide of arsenic with carbon tetrachloride and Stripping it with water.

2.2. Apparatus, reagents and solutions

Installation for electrolysis with platinum electrodes.

Photoelectrocolorimeter or spectrophotometer.

Nitric acid according to GOST 4461.

Sulfuric acid according to GOST 4204, diluted 1:4, and 3 mol/DMsolution.

Orthophosphoric acid according to GOST 6552.

Hydrochloric acid according to GOST 3118 and diluted 1:3.

The mixture of acids to dissolve one part of concentrated nitric acid and three parts concentrated hydrochloric acid.

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

Sodium hydroxide according to GOST 4328, solution 100 g/DM.

Ammonium molybdate according to GOST 3765, recrystallized from alcohol solution, a solution of 10 g/DM3 mol/DMsolution of sulphuric acid (recrystallization molybdate of ammonium is produced, as indicated in GOST 1652.12).

Potassium iodide according to GOST 4232, 0.12 mol/DMsolution in concentrated hydrochloric acid; prepared as follows: 10 g of potassium iodide dissolved in 500 cmof concentrated hydrochloric acid. The solution is prepared the day of application.

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

Hydrazine-molybdate solution; prepared as follows: to 50 cmof a solution of ammonium molybdate add 5 cmof a solution of hydrazine sulphate and dilute with water to 100 cm. Use freshly prepared solution.

Alum salesonline, solution 100 g/l; prepared as follows: 10 g of alum was dissolved with heating in 70 cmwater and 5 cmof concentrated nitric acid. The solution was filtered and diluted with water to 100 cm.

Potassium permanganate according to GOST 20490, a solution of 1 g/DM.

Carbon tetrachloride according to GOST 20288.

Phenolphthalein, solution at 10 g/lin ethanol.

The technical rectified ethyl alcohol according to GOST 18300.

The standard solutions of arsenic (see p.2.2).

(Changed edition, Rev. N 3).

2.3. Analysis

2.3.1. The weight of the alloy depending on the mass fraction of arsenic (tab.1) is placed in a beaker with a capacity of 250 cm, add 1 cmof a solution of alum salesonline (if iron is not a component of the alloy), 20 cmof the mixture of acids to dissolve, cover with a glass watch glass and dissolved under heating.

Table 1

The solution was cooled, washed with a watch glass and sides of beaker with water and dilute with water to 150 cm. To the obtained solution was added a solution of ammonia to form a dark blue ammonia complex of copper solution and kept for 30 min at a temperature of 50−60 °C for coagulation of the precipitate of iron hydroxide. The precipitate was filtered off on a medium density filter and washed 6−8 times with hot ammonia solution, diluted 1:50. The filter cake is dissolved in 25 cmhot sulphuric acid, diluted 1:4, collecting the solution in a glass, which conducted the deposition, and the filter was washed 5−7 times in hot water.

The solution was evaporated until a white smoke of sulfuric acid, then wash the side of the Cup with water and again repeat the evaporation until a white smoke of sulfuric acid. After cooling, rinse the walls of the glass 5−10 cmof water added to a glass of 0.2−0.3 g of hydrazine sulfate and heated for 5−10 min Solution was cooled.

When the mass fraction of arsenic in the alloy to 0.01% for the analysis using the full solution, adding 5 cmof phosphoric acid, while the mass fraction of arsenic more than 0.01% solution transferred to a volumetric flask with a capacity of 50 cm, pour 5 cmof phosphoric acid, made up to the mark with water, mixed and taken for analysis aliquot part (see table.1).

The entire solution or aliquot part is placed in a separating funnel with a capacity of 250 cm, the walls of the glass should be rinsed with 5 cmof water, add 60 cmof a solution of potassium iodide, 30 cmof carbon tetrachloride and extracted arsenic for 2 min. the Organic layer drained into another separatory funnel with a capacity of 100−150 cm, and in the first add 15 cmof carbon tetrachloride and repeat the extraction again. The extracts are washed for 2 minutes of 20 cmof solution, which is prepared by combining three parts of a solution of potassium iodide and one part water. The washed organic layer is drained into a third separatory funnel with a capacity of 100−150 cm, flow 15 cmof water and carry out the Stripping of arsenic by shaking for 2 min.

The organic layer is poured into the fourth separating funnel with a capacity of 100−150 cmand repeat the Stripping under the same conditions. Water layers merge into a measuring flask with a capacity of 50 cm, is added dropwise a solution of potassium permanganate until pink colour, which is then eliminated by adding dropwise a solution of hydrazine sulfate. To the resulting solution was added to 4 cmof freshly prepared hydrazine-molybdenum solution and the flask with reaction mixture was placed in a boiling water bath. In 10−15 min the solution was cooled, made up to the mark with water, mix and measure optical density on a photoelectrocolorimeter with a red light filter (at a wavelength of 656−700 nm) in a cuvette with a layer thickness of 5 mm or spectrophotometer in a cuvette with a layer thickness of 1 cm at a wavelength of 840 nm. Solution comparison is the solution of the control experiment through all stages of the analysis.

2.3.2. Construction of calibration curve

Six glasses with a capacity of 250 cm,add 1 cmof solution gentoomaniac alum and administered consistently 0; 1,0; 2,0; 3,0; 4,0 and 5,0 cmstandard solution B. To each beaker was added 20 cmof the mixture of acids to dissolve and further analysis are as indicated in claim 2.3.1.

On the found values of optical densities build the calibration graph.

2.4. Processing of the results

2.4.1. Mass fraction of arsenic , in percent calculated by the formula

,

where is the mass of arsenic, was found in the calibration schedule g;

 — weight (or maintain it in aliquotes part),

2.4.2. The absolute discrepancies in the results of parallel measurements ( — convergence) must not exceed the permissible values given in table.2.

Table 2

2.4.3. The absolute discrepancies of the analysis results obtained in two different laboratories or two of the results obtained in the same laboratory but under different conditions (the reproducibility) shall not exceed the values specified in table.2.

2.4.2, 2.4.3. (Changed edition, Rev. N 2, 3).

2.4.4. The control accuracy of the analysis carried out according to State standard samples (GSO) or industry standard sample (CCA), or by standard samples of the enterprise (SOP) copper-zinc alloys, approved under GOST 8.315, or by additives or by comparing the results obtained by another method in accordance with GOST 25086.

(Changed edition, Rev. N 3).

2.4.4.1−2.4.4.3. (Deleted, Rev. N 3).

3. AMPEROMETRIC METHOD FOR THE DETERMINATION OF ARSENIC

3.1. The essence of the method

The method is based on the Stripping of arsenic from hydrochloric acid medium in the form of chloride of arsenic, and the amperometric titration solution mixtures bromoperoxidase and bromide of potassium.

3.2. Apparatus, reagents and solutions

Amperometric installation with a rotating platinum electrode and a saturated calomel reference electrode.

Apparatus for distillation of arsenic GOST 14204.

Hydrochloric acid according to GOST 3118 or GOST 14261, diluted 1:1 and 1 mol/DMsolution.

The mixture of acids to dissolve consisting of one part concentrated nitric acid and three parts concentrated hydrochloric acid.

Nitric acid according to GOST 4461.

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

Arsenious anhydride.

Sodium hydroxide according to GOST 4328, mol/DMsolution.

Hydrogen peroxide according to GOST 10929, 30% solution.

Hydrazine sulfate according to GOST 5841.

Potassium bromide according to GOST 4160.

Potassium branovitskiy.

Solution arsenic standard; prepared as follows: 0,1320 g of arsenious anhydride is dissolved in 5 cm1 mol/DMsolution of sodium hydroxide, dilute with water and add 10 cm1 mol/DMhydrochloric acid solution, transfer the solution into volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.002 g of arsenic.

The mixture bromoperoxidase and bromide of potassium; prepared as follows: 0,1392 g polnovatogo potassium, 1 g of potassium bromide dissolved in water, transferred to a volumetric flask with a capacity of 1 DM, made up to the mark and mix.

The installation of the mass concentration of the mixture bromoperoxidase and bromide of potassium. In a glass with a capacity of 400 cmtaken 15−20 cmof a standard solution of arsenic, and add 100 cmof hydrochloric acid diluted 1:1, 100 cmof water, heated to 40−50 °C and titrated with a solution mixture of potassium bromide and Bromeliaceae amperometric, as specified in clause 3.3.

The mass concentration of the solution bromoperoxidase and bromide of potassium , expressed in grams of arsenic per milliliter, calculated by the formula

,

where is the mass of arsenic taken for the titration, g;

 — the volume of the mixture solution bromoperoxidase and bromide of potassium consumed in the titration, sm.

(Changed edition, Rev. N 3).

3.3. Analysis

A sample of alloy weighing 3 g were placed in a glass with a capacity of 300−400 cm, add 30 cmof nitric acid, diluted 1:1, cover with a watch glass and heated until dissolved. After dissolution of the sample clock glass and sides of beaker are washed with a small amount of water and remove the oxides of nitrogen by boiling.

The solution is poured into 30 cmof sulphuric acid diluted 1:1, and heated to produce abundant white smoke of sulfuric acid. The residue is cooled, wash the side of the Cup with water and again heat the solution to release white smoke of sulfuric acid, then the residue is cooled and dissolved salts in small amount of water (about 20 cm), transferred the solution into the distillation flask of the apparatus for distillation of arsenic. After this solution was added 1 g of dry mixture of hydrazine with potassium bromide, and connect the flask with a refrigerator.

Then rinse the glass (which was produced by the decomposition of the sample) of concentrated hydrochloric acid and transfer it through the funnel into the distillation flask.

Poured into a flask of 50 cmof concentrated hydrochloric acid and distilled arsenic in the form of trichloride, driving 2/3 of the original volume, with a uniform boiling (for uniform boiling in a flask placed glass beads). The distillate collected in the flask-receiver with a capacity of 250 cm, containing 20−30 cmof water. In order to avoid partial volatilization of the arsenic attached to the control receiver with 10−15 cmof water. The distillate was transferred to a beaker with a capacity of 400 cm, heated to 40−50 °C and immediately titrated with a solution mixture of potassium bromide and Bromeliaceae on amperometric install. Electrodes are attached to a sensitive galvanometer. The equivalence point find graphically as the intersection point of two straight lines in the coordinates: the current — volume of the titrant solution.

3.4. Processing of the results

3.4.1. Mass fraction of arsenic , in percent calculated by the formula

,

where is the volume of solution of a mixture bromoperoxidase and bromide of potassium consumed in the titration, cm;

 — mass concentration of a solution of a mixture bromoperoxidase and bromide of potassium, expressed in g/cmof arsenic;

 — the weight of the portion of alloy,

(Changed edition, Rev. N 3).

3.4.2. The absolute discrepancies in the results of parallel measurements (-convergence) must not exceed the permissible values given in table.2.

3.4.3. The absolute discrepancies of the analysis results obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (the reproducibility) shall not exceed the values specified in table.2.

3.4.2, 3.4.3. (Changed edition, Rev. N 2, 3).

3.4.4. The control accuracy of the analysis carried out according to State standard samples (GSO) or industry standard sample (CCA), or by standard samples of the enterprise (SOP) copper-zinc alloys, approved under GOST 8.315, or by additives or by comparing the results obtained by another method in accordance with GOST 25086.

3.4.4.1−3.4.4.3. (Deleted, Rev. N 3).

4. THE PHOTOMETRIC METHOD FOR THE DETERMINATION OF ARSENIC

4.1. The essence of the method

The method is based on preliminary separation of arsenic transport in the form of chloride of arsenic, the formation of yellow michalopolous complex with subsequent restoration to michalopolous blue and measuring optical density of colored solution at a wavelength of 830 nm.

4.2. Apparatus, reagents and solutions

Spectrophotometer or photoelectrocolorimeter.

Apparatus for distillation of arsenic GOST 14204 or other device of a similar type.

Hydrochloric acid according to GOST 3118 and 1 mol/DM.

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

Sulfuric acid according to GOST 4204, and diluted 1:1 and 3 mol/DM.

Sodium hydroxide according to GOST 4328, 1 mole/DMsolution.

Hydrazine sulfate according to GOST 5841 and a solution of 1.5 g/l, freshly prepared.

Potassium bromide crystal according to GOST 4160.

Hydrogen peroxide according to GOST 10929, 2% solution.

Rectified ethyl alcohol according to GOST 18300.

Ammonium molybdate according to GOST 3765, recrystallized from alcohol solution, a solution of 10 g/DM3 mol/DMsulfuric acid (recrystallization of ammonium molybdate is carried out as specified in GOST 1652.12).

A mixture of a reactive hydrazine-molybdate solution; 50 cmof ammonium molybdate diluted with water to 450 cm, add 5 cmof hydrazine sulfate solution and add water to 500 cm. Use freshly prepared solution.

Arsenious anhydride.

Standard solutions of arsenic.

Solution a: 0,1320 g of arsenious anhydride is dissolved in 5 cmof sodium hydroxide solution, add 10 cmwater 10 cm1 mol/DMof hydrochloric acid and the solution transferred to a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.0002 g of arsenic.

Solution B: 10 cmsolution And taken in a volumetric flask with a capacity of 200 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.0002 g of arsenic.

(Changed edition, Rev. N 3).

4.3. Analysis

4.3.1. A sample of alloy weighing 1 g is placed in a beaker with a capacity of 40 cmand dissolved in 15 cm.of nitric acid diluted 1:1. Then add 15 cmof sulphuric acid diluted 1:1, and carefully evaporated to release white smoke of sulfuric acid. After cooling, the residue is dissolved in water and transferred into the flask of distillation apparatus. The volume of the solution diluted with water to 50 cm, add a few pieces of porous material or glass beads, 3−4 g of hydrazine sulfate, 1 g of potassium bromide and the flask attached to a distillation apparatus. Through a funnel the flask was poured 75 cmof concentrated hydrochloric acid and distilled the original volume. The distillate collected in a flask-receiver, containing 25 cmof hydrogen peroxide. The distillate is transferred to a volumetric flask with a capacity of 250 cm, add 15 cmof concentrated nitric acid, made up to the mark and mix.

Depending on the expected arsenic content is taken in a tall glass with a capacity of 150−250 cmaliquot part of the solution according to the table.4.

Table 4*

_______________

* Table.3 excluded.

Aliquot part of the solution is evaporated on a boiling water bath to dryness. Then the glass is transferred to a drying Cabinet and dried at 120 °C for 1 h. To the cooled residue add 30 cmof the reaction mixture and heated in a boiling water bath for 10 min. the solution was Then cooled, transferred to a volumetric flask with a capacity of 50 cm, add this mixture to the mark and mix. Optical density of the solution measured on a spectrophotometer at 830 nm. A solution of comparison is the solution of the reference experiment.

4.3.2. Construction of calibration curve

In six of the seven glasses with a capacity of 150−250 cmare selected 2,0; 4,0; 6,0; 8,0; 10,0; 12,0 cmstandard solution of arsenic, which corresponds to 0,02; 0,04; 0,06; 0,08; 0,10 and 0,12 mg of arsenic. All the glasses are poured at 5 cmof concentrated nitric acid and evaporated on a water bath to dryness, then over 1 h allowed to stand in a drying Cabinet at a temperature of 130 °C and then are received as specified in clause 4.3.1. Solution comparison is the solution not containing arsenic.

4.4. Processing of the results

4.4.1. Mass fraction of arsenic , in percent calculated by the formula

,

where is the mass of arsenic, was found in the calibration schedule g;

 — the volume of initial sample solution, cm;

 — the mass of sample, g;

 — volume aliquote parts of a solution of the sample, cm.

4.4.2. The absolute discrepancies in the results of parallel measurements ( — convergence) must not exceed the permissible values given in table.2.

4.4.3. The absolute discrepancies of the analysis results obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (the reproducibility) shall not exceed the values specified in table.2.

4.4.2, 4.4.3. (Changed edition, Rev. N 2, 3).

4.4.4. The control accuracy of the analysis carried out according to State standard samples (GSO) or industry standard sample (CCA), or by standard samples of the enterprise (SOP) copper-zinc alloys, approved under GOST 8.315, or by additives or by comparing the results obtained by another method in accordance with GOST 25086.

4.4.4.1−4.4.4.3. (Deleted, Rev. N 3).