GOST 12355-78

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  ГОСТ 12355-78

GOST 12355−78 (ST SEV 1506−79) Steel alloyed and high alloy. Methods for determination of copper (with Change No. 1)

GOST 12355−78

Group B39

STATE STANDARD OF THE USSR


STEEL ALLOYED AND HIGH-ALLOYED

Methods for determination of copper

Alloyed and high-alloyed steels.
Methods of copper determination

AXTU 0809

Date of introduction 1980−01−01

APPROVED AND put INTO EFFECT by decision of the USSR State Committee for standards of 23 November 1978 N 3081

PROVEN in 1984 by Decree of the state standard from 15.08.84 2877 N validity extended until 01.01.95*
_____________
* Expiration removed by Protocol No. 4−93 of the Interstate Council for standardization, Metrology and certification. (IUS N 4, 1994). — Note the CODE.

REPLACE GOST 12355−66, in addition to General guidance

REPRINT March 1986, with Change No. 1, approved in August 1984 (IUS 11−84).


This standard specifies the extraction-photometric method for the determination of copper (at a mass fraction of 0.01 to 0.10%), a photometric method (in mass fractions from 0.10 to 1.00%), the polarographic method (in mass fractions of from 0.01 to 2.00%), titrimetric method (from 1.00 to 4.00%), gravimetric method (in mass fractions of from 0.30 to 4.00%) and atomic absorption method (in mass fractions from 0.10 to 4.00%).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 20560−81.

2. EXTRACTION-PHOTOMETRIC METHOD FOR THE DETERMINATION OF COPPER (0,01−0,10%)

2.1. The essence of the method

The method is based on the formation in ammonia solution (pH of 8.5−9.0) painted in yellow color and extracted with chloroform complex compounds of copper (II) with diethyldithiocarbamate sodium.

Silicon, tungsten, niobium, titanium separated by acid hydrolysis. The effect of aluminum, molybdenum, Nickel, chromium, iron and manganese, deformity, eliminate the addition of citrate of ammonium and Trilon B.

2.2. Apparatus, reagents and solutions

Spectrophotometer, photoelectrocolorimeter, or spectropolarimeter.

Hydrochloric acid by the GOST 3118−77 or hydrochloric acid of high purity according to GOST 14261−77.

Nitric acid GOST 4461−77 or nitric acid high purity according to GOST 11125−84.

Sulfuric acid GOST 4204−77 or sulphuric acid of high purity according to GOST 14262−78 and diluted 1:1.

Orthophosphoric acid according to GOST 6552−80.

Ammonia water according to GOST 3760−79.

Salt is the disodium Ethylenediamine — N, N, N', N' — tetraoxane acid, 2-water (Trilon B) according to GOST 10652−73. A solution of 10 g Trilon B dissolved in low heat in 100 ml of water and filtered.

Chloroform.

Diethyldithiocarbamate sodium GOST 8864−71, 0.1, and 0.5% solution, freshly prepared.

Ammonium citrate, disodium GOST 3653−78, 25% solution. The solution is purified from impurities of heavy metals in the form of diethyldithiocarbamate by extraction with chloroform in a separating funnel with a capacity of 500 cm. For this to 250 cmof the solution add ammonia solution to pH of 9.0 by universal indicator to 25 cmof 0.5% aqueous solution of sodium diethyldithiocarbamate, 50 cmof chloroform and vigorously shaken for 2 min. Water and chloroform, the layers allowed to settle. The chloroform layer discarded.

Radio engineering carbonyl iron according to GOST 13610−79 OS. h

Copper metal according to GOST 546−79.

Copper sulphate, standard solutions A and B.

Solution A. 1 g of copper metal is dissolved by heating in 20−25 cmof nitric acid 1:1, add 30 cmsulphuric acid 1:1, evaporated to its release vapour and cooled. Carefully with constant stirring, add 100 cmof water. The solution was transferred to a volumetric flask with a capacity of 1 DM, cooled, made up to the mark with water and mix.

1 cmof the solution contains 1 mg of copper.

Table 1

Solution B. 10 cmstandard solution And 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 0.1 mg of copper.

Universal indicator paper.

(Changed edition, Rev. N 1).

2.3. Analysis

The weight of steel depending on the mass fraction of copper (tab.1) is placed in a beaker or flask with a capacity of 250−300 cm, 30 cm, pour thehydrochloric acid, cover with watch glass and heated to dissolve sample. Then, lightly sliding a watch glass, carefully pour the nitric acid until the termination of foaming solution and an excess of 2−3 cm. The solutions are cool, add 15 cmof sulfuric acid, 10 cmof phosphoric acid (with a mass fraction of tungsten in steel more than 3%) and the solution is evaporated prior to the allocation of sulphuric acid fumes. The solution was cooled, carefully add 25−30 cmof water with stirring and heated to dissolve the salts. The solution was transferred to a volumetric flask with a capacity of 50 or 100 cm, cooled, made up to the mark with water and mix.

The solution was filtered through two dry filter «white ribbon» in a flask with a capacity of 100 cm, rinsing the flask first portions of the filtrate.

Aliquot part of the solution is 5 cmis placed in a beaker with a capacity of 50−100 cm, flow 10 cmof a solution of 25% ammonium citrate; 10 cmof the solution Trilon B, mix and add solution of ammonia to pH 9 by universal indicator.

The solution was transferred to a separatory funnel, add water to a volume of 60−70 cm, add 5 cmof a 0.1% strength solution of sodium diethyldithiocarbamate and extracted 10 cmof chloroform, vigorously shaking the solution for 2 min. Water and chloroform, the layers allowed to settle and decanted chloroform layer in a dry volumetric flask with a capacity of 25 cm. The separating funnel aqueous solution was added to 5 cmof chloroform, and shake it again for 2 min. After settling of the solution, the chloroform layer decanted into the same flask, after the first extraction, refill volume of the combined extracts with chloroform to the mark and mix.

Optical density of the solution measured immediately upon extraction on a spectrophotometer or spectropolarimetry at =436 nm or photoelectrocolorimeter with a filter having a region of transmittance in the wavelength range of from 380 to 430 nm in a cuvette with a thickness of the absorbing layer of 20 mm, using as a comparison solution of chloroform. The copper content found at the calibration schedule subject to amendments the reference experiment.

2.2; 2.3. (Changed edition, Rev. N 1).

2.3.1. Construction of calibration curve

Seven of cups or flasks with a capacity of 250−300 cmis placed 0.5 g of carbonyl iron. Six of cups or flasks poured successively 0,5; 1; 1,5; 2; 2,5 and S cmstandard solution B copper sulphate, which corresponds to 0,05; 0,10; 0,15; 0,20; 0,25 and 0,30 mg of copper. The seventh beaker or flask serves for the control analysis. All beakers or flasks go for 30 cmof hydrochloric acid, cover glasses, watch glasses, and dissolve the sample when heated. Then, lightly sliding the hour glass, carefully pour the nitric acid until the cessation of the foaming of solutions and an excess of 2−3 cm.

The solutions are cool, add 15 cmof sulphuric acid, for 5 cmof phosphoric acid (with a mass fraction of tungsten in steel more than 3%) and evaporated to start the selection of sulfuric acid vapor. The solutions were cooled, carefully added at 25−30 cmof water with stirring and heated to dissolve the salts. The solutions were transferred to volumetric flasks with a capacity of 50 cm, cooled, made up to the marks with water and stirred. Further, the analysis continues as described in section 2.3, beginning with the words: «the Solution was filtered through two dry filter «white ribbon». .

From the values of absorbance of analyzed solutions is subtracted the value of optical density in the reference experiment.

The found values of optical density and corresponding concentration values of copper to build the calibration.

K.

2.4. Processing of the results

2.4.1. Mass fraction of copper () in percent is calculated by the formula

,

where is the weight of steel, suitable fotometricheskoe aliquote part of the solution, mg;

 — the mass of copper was found in the calibration schedule, mg.

(Changed edition, Rev. N 1).

2.4.2. Permissible absolute discrepancy between the outermost of the three parallel results at a confidence level = 0.95 does not exceed the values specified in table.3.

3. THE PHOTOMETRIC METHOD FOR THE DETERMINATION OF COPPER (0,10−1,00%)

3.1. The essence of the method

The method is based on the formation in ammonia solution (pH of 8.5−9.0) painted in yellow color and stabilized with gelatin complex compounds of copper (II) with diethyldithiocarbamate sodium. The interfering influence of iron, chromium, Nickel, vanadium, molybdenum, manganese, aluminum, eliminate the preliminary separation of copper as a sulfide Chernovetskiy sodium and the addition of citrate of ammonium.

Silicon, tungsten, niobium, titanium separated by acid hydrolysis.

(Changed edition, Rev. N 1).

3.2. Apparatus, reagents and solutions

Spectrophotometer, photoelectrocolorimeter, or spectropolarimeter.

Hydrochloric acid by the GOST 3118−77 or hydrochloric acid of high purity according to GOST 14261−77 diluted 1:1.

Nitric acid GOST 4461−77 or nitric acid high purity according to GOST 14262−78 and diluted 1:1, 1:4, 1:50.

Orthophosphoric acid according to GOST 6552−80.

Ammonia water according to GOST 3760−79.

The polyvinyl alcohol solution with a mass fraction of 0.2%

Citric acid according to GOST 3652−69, 20% solution.

Diethyldithiocarbamate sodium GOST 8864−71, 0,5% solution of freshly prepared.

Carbonyl iron, high purity.

Copper metal according to GOST 546−79.

Copper sulfate, standard solution A. 1 g of copper metal is dissolved by heating in 20−25 cmof nitric acid 1:1, add 30 cmsulphuric acid 1:1, evaporated to its release vapour and cooled. Cautiously, with constant stirring, add 100 cmof water. The solution was transferred to a volumetric flask with a capacity of 1 DM, cooled, made up to the mark with water and mix.

1 cmof the solution contains 1 mg of copper.

Solution B. 10 cmstandard solution And 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 0.1 mg of copper.

Sodium Chernovetskiy, 30% solution.

Table 2

Potassium preservatory according to GOST 7172−76.

Gelatin GOST 11293−78, 0,5% solution, freshly prepared.

3.3. Analysis

The weight of steel depending on the mass fraction of copper (tab.2) is placed in a beaker or flask with a capacity of 250−300 cm, flow 50 cmsulphuric acid 1:4, cover with a watch glass, gently pour 3−5 cmof nitric acid and evaporated until the appearance of sulphuric acid fumes. If the steel is not soluble in sulfuric acid, the portion dissolved in 20 cmof hydrochloric and 5−10 cmof nitric acid, and then carefully poured 15 cmsulphuric acid and 10 cmof orthophosphoric acid (the latter if the mass fraction of tungsten in steels of more than 3%) and the solution is evaporated to release vapors of sulfuric acid. The contents of the beaker or flask is cooled, carefully poured, with stirring, 80−100 cmof water, heated to dissolve the salts and filtered off the precipitate of silicon, tungsten, niobium acid on the filter «white ribbon». Precipitate was washed 7−8 times with hot sulfuric acid of 1:50, collecting the filtrate and wash liquid in a glass with a capacity of 300−400 cm. Filter the precipitate discarded.

To the resulting hot solution is poured 40−50 cmof 30% solution of sodium servational and boil until complete coagulation of the precipitate of copper sulfide and sulfur and enlightenment solution.

The solution with precipitate was cooled, the precipitate was filtered off on filter «white ribbon» and washed 6−8 times with hot water. The filter with precipitate was placed in a porcelain crucible, dried and incinerated. The precipitate was calcined at 500−550° C and melted with 2−3 g of potassium peacemaking. The smelt is dissolved in a beaker with a capacity of 100 cm15−20 cmof hydrochloric acid 1:1, add 10−15 cmof water. The solution is heated until complete dissolution of water, transferred to a volumetric flask with a capacity of 100 cm, cooled, made up to the mark with water and mix. The solution was filtered through two dry filter «white ribbon» in a dry flask, discarding first portion of filtrate. Aliquot part of the solution is placed in a volumetric flask with a capacity of 100 cm, add 15 cmof the citric acid solution, 10 cmgelatin solution or 15 cmof the polyvinyl alcohol solution and 15 cmof ammonia solution. The solution was stirred, add 10 cmof a solution of sodium diethyldithiocarbamate, made up to the mark with water, mix.

Optical density of the solution measured on spectropolarimeter at a =453 nm or photoelectrocolorimeter with a filter having a region of transmittance of wavelengths from 420 to 490 nm in a cuvette with the thickness of the absorbing layer 30 mm. as a solution comparison solution is used in the reference experiment. Mass of copper find the calibration schedule, as amended by Kont

roll experience.

3.2; 3.3. (Changed edition, Rev. N 1).

3.3.1. Construction of calibration curve

In eight glasses or flasks with a capacity of 250−300 cmis placed 0.1 g of carbonyl iron. Seven of cups or flasks poured consistently 1, 2, 4, 6, 8, 10 and 12 cmstandard solution B copper sulphate, which corresponds to 0,1; 0,2; 0,4; 0,6; 0,8; 1,0 and 1.2 mg of copper. The eighth beaker or flask serves for the control experience. All beakers or flasks poured 20 cmof hydrochloric acid, cover with watch glass and dissolve the sample when heated. Then, lightly sliding the hour glass, carefully pour the nitric acid until the cessation of the foaming of solutions and a plethora of 2−3 cm. The solutions are cool, add 10 cmsulphuric acid and 5 cmof orthophosphoric acid (the latter if the mass fraction of tungsten in steels of more than 3%) and evaporated the solvents to start the selection of sulfuric acid vapor. Further, the analysis continues as described in section 3.3, beginning with the words: «the Contents of the beaker or flask is cooled, carefully poured, with stirring, 80−100 cmof water, heated to dissolve the salts… «.

From the values of absorbance of analyzed solutions is subtracted the value of optical density in the reference experiment. The found values of optical density and corresponding concentration values of copper build calibration curve

.

3.4. Processing of the results

3.4.1. Mass fraction of copper () in percent is calculated by the formula

,

where is the weight of steel, suitable fotometricheskoe aliquote part of the solution, mg;

 — the mass of copper was found in the calibration schedule, mg.

(Changed edition, Rev. N 1).

3.4.2. Permissible absolute discrepancy between the outermost of the three parallel results at a confidence level =0.95 does not exceed the values specified in table.3.

4. POLAROGRAPHIC METHOD FOR THE DETERMINATION OF COPPER (0,01−2,00%)

4.1. The essence of the method

The method is based on the deposition of copper in the form of Chernovetskiy sodium sulfide and separating the precipitate by filtration from iron, chromium, Nickel, vanadium and several other elements. Analysis done by polarography ammonium complex copper at a potential of half-wave (peak) is equal to — 0.45 V (relative to the mercury anode).

4.2. Apparatus, reagents and solutions

Polarograph electronic.

Hydrochloric acid by the GOST 3118−77 or hydrochloric acid of high purity according to GOST 14261−77 and diluted 1:1.

Nitric acid GOST 4461−77 or nitric acid high purity according to GOST 11125−84 and diluted 1:1.

Sulfuric acid GOST 4204−77 or sulphuric acid of high purity according to GOST 14262−78 and diluted 1:1, 1:4, 1:9 and 1:50.

Ammonia, aqueous solution according to GOST 3760−79.

Sodium Chernovetskiy, 30% solution.

Potassium preservatory according to GOST 7172−76.

Sanitarily sodium (sodium sulfite) anhydrous GOST 429−76.

Gelatin GOST 11293−78, a 0.5% solution.

Radio engineering carbonyl iron according to GOST 13610−79, OS. h

Copper metal according to GOST 546−79.

Copper sulphate, standard solutions A and B.

Solution A. 1 g of copper metal is dissolved by heating in 20−25 cmof nitric acid 1:1, add 30 cmsulphuric acid 1:1, evaporated to its release vapour and cooled. Carefully with constant stirring, add 100 cmof water. The solution was transferred to a volumetric flask with a capacity of 1 DM, cooled, made up to the mark with water and mix.

1 cmof the solution contains 1 mg of copper.

Solution B. 10 cmstandard solution And 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 0.1 mg med

I.

4.3. Analysis

The weight of steel

0.5 g when the mass fraction of copper from 0.01 to 0.2%,

0.2 g «"""St. 0,2» 1%,

or 0.1 g «"""" 1 «2%

placed in a glass or flask with a capacity of 200−300 cm, flow 50 cmsulphuric acid 1:4, cover with a watch glass, gently pour 3−5 cmof nitric acid and evaporated until the appearance of sulphuric acid fumes. If the steel is not soluble in sulfuric acid, the portion dissolved in 30 cmof hydrochloric and 10 cmof nitric acid and then carefully poured 10 cmof sulphuric acid and evaporate the solution until the appearance of her vapours.

The contents of the beaker or flask is cooled, carefully poured, with stirring, 80−100 cmof water, heated to dissolve the salts and filtered off the precipitate of silicon, tungsten, niobium acids on the filter «white ribbon». Precipitate was washed 7−8 times with hot sulfuric acid of 1:50, collecting the filtrate and wash liquid in a glass with a capacity of 300−400 cm. Filter the precipitate discarded.

To the obtained solution poured 40−50 cmof hot 30% solution of sodium servational and boil until complete coagulation of the precipitate of copper sulfide and sulfur and enlightenment solution.

The solution with precipitate was cooled, the precipitate was filtered off on filter «white ribbon» and washed 6−8 times with hot water. The filter with precipitate was placed in a porcelain crucible, dried and incinerated; the precipitate is calcined at 500−550° C and melted with 2−3 g of potassium peacemaking.

The smelt is leached in 20−25 cmsulphuric acid 1:9 in a beaker with a capacity of 250−300 cmand the solution is evaporated to a volume of approximately 5 cm. The contents of the beaker transferred to a volumetric flask with a capacity of 50 cm, add 5 cmof water, carefully poured with stirring 25 cmof ammonia solution, 1 cmof 0.5% aqueous gelatin solution and stirred. Add 0.5 g of sodium semitecolo, made up to the mark with water, mix and leave to stand for 5−10 min.

Part of the solution is filtered in the cell and polarographic when the voltage on the electrodes -0.3 to -0.6 V.

Mass of copper found by the calibration graph with amendments, the control

wow experience.

4.2; 4.3. (Changed edition, Rev. N 1).

4.3.1. Construction of calibration curve for the mass concentration of copper in the steel is from 0.01 to 0.20%

Twelve cups or flasks with a capacity of 200−300 cmwas placed 0.5 g of carbonyl iron. Eleven beakers or flasks poured consistently 0,5; 1; 2; 3; 4; 5; 6; 7; 8; 9 and 10 cmstandard solution B copper sulphate, which corresponds to 0,05; 0,1; 0,2; 0,3; 0,4; 0,5; 0,6; 0,7; 0,8; 0,9 and 1 mg of copper. Twelfth beaker or flask serves for the control experience.

All the glasses or the flask poured 50 cmsulphuric acid 1:4, cover with a watch glass, carefully pour 3−5 cmof nitric acid and evaporated until the appearance of sulphuric acid fumes.

Then do as described in section 4.3.

From the height of the polarographic wave (peak polarogram) analyzed solutions subtract the value of the height of the polarographic wave (peak polarogram) control experience.

The found values of the height of the polarographic wave (peak polarogram) and their corresponding concentrations of copper to build the calibration graph.

4.3.2. The construction of a graded graph when the mass fraction of copper in the steel is from 0.2 to 2.00%

Ten glasses or flasks with a capacity of 200−300 cmis placed 0.2 g carbonyl iron. Nine of cups or flasks poured consistently 4, 6, 8, 10, 12, 14, 16, 18 and 20 cmstandard solution B copper sulphate, which corresponds to 0,4; 0,6; 0,8; 1,0; 1,2; 1,4; 1,6; 1,8 and 2.0 mg of copper.

The tenth beaker or flask serves for the control analysis. All the glasses or the flask poured 50 cmsulphuric acid 1:4, cover with a watch glass, carefully pour 3−5 cmof nitric acid and evaporated until the appearance of sulphuric acid fumes.

Then do as described in section 4.3.

From the height of the polarographic wave (peak polarogram) analyzed solutions subtract the value of the height of the polarographic wave (peak polarogram) control experience.

The found values of the height of the polarographic wave (peak polarogram) and their corresponding concentrations of copper to build the calibration graph.

4.4. Processing of the results

4.4.1. Mass fraction of copper () in percent is calculated by the formula

,

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

the weight of steel, mg

;

4.4.2. Permissible absolute discrepancy between the outermost of the three parallel results at a confidence level =0.95 does not exceed the values specified in table.3.

Table 3

5. TITRIMETRIC METHOD FOR THE DETERMINATION OF COPPER (1,00−4,00%)

5.1. The essence of the method

Copper is separated from iron, chromium and other elements deposition Chernovetskiy sodium in the form of copper sulfide (I) is then separated from the vanadium and molybdenum by precipitation with sodium hydroxide. Copper (II) is reduced to copper (I) potassium iodide and titrated liberated the iodine solution servational sodium.

5.2. Reagents and solutions

Hydrochloric acid by the GOST 3118−77.

Nitric acid GOST 4461−77 and diluted 1:3.

Sulfuric acid GOST 4204−77 and diluted 1:1, 1:9, 1:50.

Sodium Chernovetskiy, 30% solution.

Potassium preservatory according to GOST 7172−76.

Sodium hydroxide according to GOST 4328−77, 10% and 0.5% solutions.

Ammonia, aqueous solution according to GOST 3760−79.

Acetic acid GOST 61−75, 80−90% solution.

Sodium fluoride according to GOST 4463−76.

Potassium iodide according to GOST 4232−74.

Universal indicator paper.

The soluble starch according to GOST 10163−76, 0,2% solution. 0.4 g of starch is stirred in 50 cmof water, add 150 cmof hot water, heat and boil for 1 min.

Copper metal according to GOST 546−79.

Copper sulfate, standard solution. 1 g of copper metal is dissolved in 10−12 cmof nitric acid 1:1 at the moderate heating. The solution was cooled, carefully poured 10 cmof sulphuric acid and evaporated until the appearance of its vapors. Again cool the solution, watch glass and walls of beaker is washed with water, and again evaporate the solution until the appearance of sulphuric acid fumes and cooled. Pour 200−300 cmof water, transferred to a volumetric flask with a capacity of 1 DM, cooled, made up to the mark with water and mix.

1 cmof this solution contains 0.001 g of copper.

Sodium Chernovetskiy according to ST SEV 223−75, titrated solution. Chernovetskogo of 12.4 g of sodium is dissolved in 1 DM, svejeprokipachenna and chilled water and set the mass concentration after 2−3 days. The solution was stored in a flask made of dark glass.

The mass concentration of a solution of sodium servational set by the standard solution of copper sulphate. 15−20 cmof a solution of copper sulphate is placed in a beaker with a capacity of 250−300 cmand 40−50 cm pouredwater. To the solution was added dropwise ammonia solution until blue color, is heated to the disappearance of the smell of ammonia, pour the acetic acid to dissolve the residue, and 5−6 cm. The solution was cooled, added to 1.5−2 g of potassium iodide and mix.

The liberated iodine is titrated with a solution of sodium servational before moving brown to light yellow. Then pour 3−5 cmstarch solution and continue the titration, dropwise adding a solution of sodium servational until the disappearance of blue color.

The mass concentration of the solution servational sodium (), expressed in grams of copper, calculated by the formula

,

where is the copper content in 1 cmstandard solution, g;

 — the volume of a standard solution of copper sulphate, are taken for titration, cm;

the volume of the solution servational sodium, spent on titration, sm.

5.3. Analysis

The weight began weight

1 g when the mass fraction of copper 1 to 2% and

0.5 g «"""St… 2» 4%

placed in a beaker with a capacity of 300−400 cm, flow 50 cmsulphuric acid 1:4, the beaker cover watch glass, and heated to dissolve sample. Carefully pour 3−5 cmof nitric acid and evaporate the solution until the appearance of sulphuric acid fumes.

If the linkage is not soluble in sulfuric acid, dissolution is carried out in a mixture of 30 cmof hydrochloric and 10 cmof nitric acid. Then gently pour the 10 cmof sulphuric acid and evaporate the solution until the appearance of her vapours.

The contents of the beaker cooled, poured 80−100 cmof water, heated to dissolve the salts and filtered off the precipitate of silicon (tungsten, niobium acid) to the filter «white ribbon». Precipitate was washed 7−8 times with hot sulfuric acid of 1:50, collecting the filtrate and wash liquid in a glass with a capacity of 300−400 cm. Filter the precipitate discarded.

To the obtained solution poured 30−35 cmhot 30% solution of sodium servational and boil until complete coagulation of the precipitate of copper sulfide and sulfur. Then the solution with precipitate was cooled, the precipitate was filtered off on filter «white ribbon» and washed 6−8 times with hot water. The filter with precipitate was placed in a porcelain crucible, dried, incinerated, and calcined at 500−550° C, fused with 1−2 g of potassium peacemaking and dissolve the fusion in 20−25 cmsulphuric acid 1:9 in a beaker with a capacity of 250−300 cm.

The solution is diluted with water to 100 cmand add 10% sodium hydroxide solution to pH 7−8 by universal indicator paper. Add another 0.3−0.5 cm10% sodium hydroxide solution, boiled for 3 min and left for 30 minutes in a warm place.

The precipitate was filtered off on filter «white ribbon» and washed 5−6 times with 0.5% strength sodium hydroxide solution. The filtrate and the wash liquid discarded.

The precipitate is dissolved in 15−25 cmof hot nitric acid 1:3 and washed the filter with hot water, collecting the solution and wash liquid into the glass, which made the deposition.

The solution is poured 5 cmsulphuric acid 1:1 and evaporated to the appearance of its vapors. Cool, the side of the Cup washed with water and again evaporate the solution until the appearance of sulphuric acid fumes. The contents of the beaker cooled, poured 50−60 cmof water and heated to dissolve the salts.

To sulphate solution are added dropwise ammonia solution until blue color, is heated to the disappearance of the smell of ammonia, pour the acetic acid to dissolve the residue, and 5−6 cm. The solution was cooled, was added 0.3 g of sodium fluoride and 1.5−2 g of potassium iodide, stirring the solution after addition of each reagent. Beaker cover watch glass and leave in dark place for 3−5 min.

The liberated iodine is titrated with a solution of sodium servational before moving brown color of the solution in light yellow. Then pour 3−5 cmstarch solution and continue the titration, dropwise adding a solution of sodium servational until the disappearance of blue color.

(Amended

, Edit. N 1).

5.4. Processing of the results

5.4.1. Mass fraction of copper () in percent is calculated by the formula

,

where  — volume of the solution servational sodium consumed for titration, cm;

The mass concentration of the solution chernovetskogo of sodium, expressed in grams of copper;

 — the weight of the portion,

5.4.2. Permissible absolute discrepancy between the outermost of the three parallel measurements at a confidence level =0.95 does not exceed the values specified in table.4.

(Changed edition, Rev. N 1).

6. GRAVIMETRIC METHOD FOR DETERMINATION OF COPPER (0,30−4,00%)

6.1. The essence of the method

The method is based on the electrolytic release of copper from acidic solution. Copper pre-separated from iron, chromium and other elements deposition Chernovetskiy sodium. In the presence of molybdenum copper is additionally separated with lye.

6.2. Apparatus, reagents and solutions

The electrodes are platinum mesh.

Variable Resistor 1400 Ohm, 0,25 A.

Voltmeter.

Ammeter.

The mixers 200−300 rpm.

Hydrochloric acid by the GOST 3118−77.

Nitric acid GOST 4461−77 and diluted 1:1, 1:3.

Sulfuric acid GOST 4204−77 and diluted 1:1, 1:9, 1:50.

Sodium Chernovetskiy, 30% solution.

Potassium preservatory according to GOST 7172−76.

Sodium hydroxide according to GOST 4328−77, 10% and 0.5% solutions.

Ethyl alcohol according to GOST 5962−67.

Universal indicator paper.

6.3. Analysis

The weight of steel

2 g when the mass fraction of copper from 0.3 to 1%,

1 g «"""St… 1» 2%,

0.5 g «"""" 2 «4%

placed in a beaker with a capacity of 200−300 cm, flow 50 cmsulphuric acid 1:4, the beaker cover watch glass, and heated to dissolve sample. Then, lightly sliding a watch glass, gently pour 3−5 cmof nitric acid and evaporated until the appearance of sulphuric acid fumes.

If the steel is not soluble in sulphuric acid 1:4, then the sample is dissolved in 30 cmof hydrochloric acid and 10 cmof nitric acid, carefully pour 10 cmof sulphuric acid and evaporate the solution until the appearance of sulphuric acid fumes.

The contents of the beaker cooled, poured 80−100 cmof water, heated to dissolve the salts and filtered off the precipitate of silicon (tungsten, niobium acid) to the filter «white ribbon». Precipitate was washed 7−8 times with hot sulfuric acid of 1:50, collecting the filtrate and wash liquid in a glass with a capacity of 300−400 cm.

The filter with the sediment is discarded and to the obtained solution poured 30−35 cmhot 30% solution of sodium servational and boil until complete coagulation of the precipitate of copper sulfide and sulfur. Then, the solution and the precipitate leave on for 5−10 min, the precipitate was filtered off on filter «white ribbon» and washed 6−8 times with hot water. The filter with precipitate was placed in a porcelain crucible, dried, incinerated, and calcined at 500−550 °C, fused with 1−2 g of potassium peacemaking and dissolve the fusion in 20−25 cmsulphuric acid 1:9 in a beaker with a capacity of 250−300 cm.

The solution is diluted with water to 100 cm, neutralized to the universal indicator 10% sodium hydroxide solution a pH of 7−8, is added an excess (0.3−0.5 cm), boiled for 2−3 min and leave for 30 minutes in a warm place. The precipitate is then filtered off on filter «white ribbon», washed 5−6 times in 0.5% sodium hydroxide solution, the filtrate and the wash liquid discarded.

The precipitate is dissolved in 12−15 cmof hot nitric acid 1:3, and the filter washed 7−8 times with hot water, collecting the solution and wash liquid into the glass, which made the deposition. The solution is poured 4−5 cmsulphuric acid 1:1 and diluted with water to 150−170 cm.

The electrodes are washed with nitric acid of 1:1 with water, then the cathode is washed with alcohol, dried at 95−100 °C, cooled and weighed. The prepared electrodes immersed in the glass with a solution and the solution is electrolyzed at a current of 1 A and a voltage of 2−2,5 V for 30 min with constant stirring of the solution.

The completeness of separation of copper test, immersing a clean cathode surface to 3−4 mm in the electrolyte or priliva into the beaker with the test solution is 15−20 cmof water. If on the newly immersed surface of the cathode after 5 min will not have a plaque of copper, electrolysis is complete. Without interrupting the current, wash the cathode with water, then turn off the current, disconnect the cathode from the terminals, washed with ethanol, dried at 95−100° C for 1−2 min, cooled and weighed.

(Amended,

Izm. N 1).

6.4. Processing of the results

6.4.1. Mass fraction of copper () in percent is calculated by the formula

,

where is the mass of sample, g;

the mass of the electrode with the copper precipitate, g;

the mass of the electrode without sediment copper, g;

the mass of the electrode with the precipitate obtained in control experiment g;

the mass of the electrode without sediment in a control experiment,

6.4.2. Permissible absolute discrepancy between the outermost of the three parallel measurements at p = 0.95 does not exceed the values specified in table.4.

(Changed edition, Rev. N 1).

7. ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF COPPER (0,10−4,00%)

7.1. The essence of the method

The method is based on measuring the degree of absorption of resonance radiation by free atoms of copper, formed as a result of spraying the test solution in a flame air-acetylene.

Weighed sample was dissolved in a mixture of hydrochloric and nitric acids, evaporate the solution to dryness, the dry residue is dissolved in hydrochloric acid. After appropriate dilution of the solution used for the determination of copper by atomic absorption method.

7.2. Apparatus, reagents and solutions

Atomic absorption spectrophotometer fiery.

Lamp with hollow cathode for the determination of copper.

The cylinder with acetylene.

The compressor supplying compressed air, or compressed air.

Hydrochloric acid by the GOST 3118−77.

Nitric acid GOST 4461−77.

Copper metal according to GOST 546−79.

Copper nitrate, standard solutions A and B.

Solution A. 1 g of copper metal is dissolved by heating in 20 cmof nitric acid 1:1. The solution was cooled, transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof the solution contains 1 mg of copper.

Solution B. 10 cmof the solution And 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 0.1 mg of copper.

Preparation of the device

Training device produced in accordance with the attached instructions. Set the spectrophotometer at a resonance line of 324,7 nm. After switching on the gas flow and ignition of the burner spray water and set the zero of the instrument.

7.3. Analysis

Weighed 0.1 g of steel placed in a beaker with a capacity of 100 cm, 8 cm poursalt and 2 cmof nitric acid and heated to dissolve sample. The solution was evaporated to dryness and the dry residue is dissolved in 4 cmof hydrochloric acid. Pour 20−30cmof water, transfer the solution into a measuring flask with a capacity of 100 cm, made up to the mark with water and mix.

The resulting solution was filtered through a dry filter «white ribbon» in a dry conical flask by rinsing it the first portions of the filtrate. The copper content in excess of 1% solution is diluted so that its content was not more than 0.01 mg/ml, and the content of hydrochloric acid — 4 cmto 100 cm.

Spend control experience. Spray the solution in the reference experiment and the sample solution to obtain stable results, for each solution. Before spraying each solution is sprayed water to obtain the zero index of the device.

Construction of calibration curve

In a volumetric flask with a capacity of 100 cmplaced 1, 3, 5, 7, 9 and 11 cmstandard solution of copper nitrate, which corresponds to 0,1; 0,3; 0,5; 0,7; 0,9 and 1,1 mg of copper. Add 4 cmof hydrochloric acid, dilute to the mark with water and mix.

For preparation of the null solution in a volumetric flask with a capacity of 100 cmis placed 4 cmof hydrochloric acid, made up to the mark with water and mix.

The solutions were sprayed in order of increasing absorption, starting from the zero solution. Before spraying each solution is sprayed water.

From the average value of the optical density of each solution is subtracted the average value of the optical density of the zero solution.

On the found values of optical density and their corresponding concentrations of copper build calibration

schedule.

7.4. Processing of the results

Calculate the average value of the optical density of the solution in the reference experiment and subtracted this value from the average value of the optical density of the tested solutions. According to the calibration schedule find the mass of copper in milligrams of the test solution.

7.3; 7.4 (Revised edition, Edit. N 1).

7.4.1. Mass fraction of copper () in percent is calculated by the formula

,

where  — the weight of the portion corresponding to fotometricheskoe aliquote part of the solution, mg;

 — the mass of copper was found in the calibration schedule, mg.

7.4.2. Allowable absolute differences between the extreme results of three parallel measurements at a confidence level =0.95 does not exceed the values specified in table.4.

Table 4