GOST 13938.15-88

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  ГОСТ 13938.15-88

GOST 13938.15−88 Copper. Methods for determination of chromium and cadmium

GOST 13938.15−88

Group B59

STATE STANDARD OF THE USSR

COPPER

Methods for determination of chromium and cadmium

Copper. Methods for determination of chromium and cadmium

AXTU 1709

Valid from 01.01.1990
until 01.01.2000*
________________________________
* Expiration removed by Protocol No. 7−95
The interstate Council for standardization,
Metrology and certification (I & C N 11, 1995). -
Note the manufacturer’s database.

INFORMATION DATA

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

PERFORMERS

B. M. Rogov, E. N. Gazalov, I. Swan, L. I. Igoshev, V. N. Fedorov, Y. M. Leybov, Yu. M. Dedkov, A. N. Boganova

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from 21.12.88 N 4374

3. The term of the first check — 1994

The frequency of inspection — 5 years

4. The standard corresponds to the international standards of ISO and ISO 4744−84 5960−84

5. INTRODUCED FOR THE FIRST TIME

6. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard establishes the atomic absorption and polarographic (with a mass fraction of 0.0005 to 0.00005%) methods for determination of chromium atomic absorption (at a mass fraction of up to 0,00002 0,0005%) method for the determination of cadmium in copper, grades M00k, M00b in accordance with GOST 859*.
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* On the territory of the Russian Federation GOST 859−2001, here and hereafter. — Note the manufacturer’s database.

Methods can be applied for the determination of chromium and cadmium in copper other grades according to GOST 859.

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 22306.

1.2. Selection and preparation of samples for chemical analysis according to GOST 24231. Method of sampling, weight of sample — according to GOST 546*, GOST 193.
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* On the territory of the Russian Federation GOST 546−2001. — Note the manufacturer’s database.

1.3. Mass fraction of chromium and cadmium is determined not less than two batches of copper. Simultaneously with the analysis under the same conditions is carried out two control expertise to make the relevant amendment in the result of the analysis by subtracting the value of the reference experience from the result of the determination in the analysis sample.

1.4. The final result of the analysis be the arithmetic mean of results of two parallel measurements.

The numerical value of the result of the analysis should be terminated with a figure the same category as the value of the admitted discrepancies in the results of parallel measurements specified in methods of analysis.

1.5. Terms relating to the degree of heating of water (solution) and duration of operations, apply in accordance with GOST 27025.

1.6. Control of the correctness of the results of the analysis carried out on standard samples of composition of copper any category or by a method of additives according to GOST 25086.

The results of the analysis you think is right, if you played mass fraction of this component in the standard sample differs from the certified characteristics are not more than the value of 0.71, which is the method of analysis.

When using the method supplements the results of the analysis are considered correct if the found value differs from the additive introduced its value of not more than 0.71, where and  — the permissible discrepancy of the two results of the analysis for the sample and the sample with the additive, respectively.

1.7. Safety requirements when performing tests according to GOST 13938.1.

2. ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF CHROMIUM

2.1. The essence of the method

The method is based on measuring absorption of resonance lines of chromium at a wavelength of 357,9 nm with the introduction of the analyzed solution in the flame acetylene-air after the separation of copper by electrolysis.

2.2. Equipment, accessories, utensils

Electrolysis installation DC.

Electrodes made of platinum mesh according to GOST 6563.

Atomic absorption spectrophotometer of any type.

Lamp with hollow cathode for chrome.

Acetylene according to GOST 5457.

Air compressor.

Laboratory scales analytical any type of the 2nd accuracy class with the error of weighing according to GOST 24104*.
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* On the territory of the Russian Federation GOST 24104−2001. — Note the manufacturer’s database.

Volumetric flasks 2−100 (1000)-2 GOST 1770.

Vial measuring P-2−10−0,2 KHS GOST 1770.

Glass N-1−250 (400) TC GOST 25336.

Pipette 7−2-10 according to GOST 20292*.
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* On the territory of the Russian Federation are: 29169−91 GOST, GOST 29227−91−29229−91 GOST, GOST 29251−91-GOST 29253−91, here and hereafter. — Note the manufacturer’s database.

2.3. Reagents and solutions

Nitric acid of high purity according to GOST 11125 or nitric acid according to GOST 4461 (boiled to remove oxides of nitrogen or distilled in quartz apparatus) and diluted 1:1.

Hydrochloric acid of high purity according to GOST 14261, or hydrochloric acid according to GOST 3118, diluted 1:1.

Sulfuric acid of high purity according to GOST 14262 or sulfuric acid according to GOST 4204, diluted 1:1.

Potassium dichromate according to GOST 4220, recrystallized and dried to constant weight at a temperature of 140−150 °C.

Chrome according to GOST 5905.*

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* On the territory of the Russian Federation GOST 5905−2004. — Note the manufacturer’s database.

Copper according to the GOST 859.

Potassium chromate according to GOST 4459.

Distilled water according to GOST 6709, further purified by distillation in quartz apparatus (or glass apparatus) according to GOST 4517.

Hydrogen peroxide according to GOST 10929 stable.

Standard samples for composition of copper with a certified characteristic of chromium (cadmium).

2.4. Preparation for assay

2.4.1. Preparation of standard solutions

Solution A

Method 1: a suspension of potassium dichromate mass 0,2828 g, previously recrystallized and dried, placed in a beaker with a capacity of 100 cm, flow 20 cmof water and stirred to dissolve the sample. Then add 1 cmof sulfuric acid and, after cooling, poured hydrogen peroxide prior to the termination of the rapid evolution of gas. Leave at room temperature until complete disappearance of the yellow color (a few hours). Then transferred into a measuring flask with volume capacity of 1000 cm, flow 10 cmof hydrochloric acid, dilute to the mark with water and mix.

1 cmof solution A contains 0.1 mg of chromium.

Method 2: a suspension of chromium mass of 0.10 g was placed in a beaker with a capacity of 100 cm, add 10 cmof hydrochloric acid and heated to dissolve the sample in a boiling water bath. Then the solution is evaporated to dry salts, add 5 cmof nitric acid and the solution was evaporated to wet salts. The processing operation of the salts of nitric acid is carried out three times. To wet salts in a glass poured 50−70 cmof nitric acid (1:1) and the resulting solution placed in a measuring flask with volume capacity of 1000 cm, is diluted to the mark with nitric acid (1:1) and stirred.

From the resulting solution take aliquot part of 10−20 cmand placed it in a glass with a capacity of 50 cmto test for the presence in solution of chloride ion with silver nitrate. If the solution detected a chloride ion, a nitric acid treatment of samples chromium repeat.

Method 3: a suspension of potassium chromological weight 0,3735 g is placed in a measuring flask with volume capacity of 1000 cm, is diluted to the mark with water and mix. The solution is prepared before use, its properties are saved for one day.

Solution B:

Aliquot part 10 cmof the solution And placed in a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

1 cmof a solution contains 0.01 mg of chromium.

2.4.2. Preparation of solutions comparison

Five volumetric flasks with a capacity of 100 cmis placed 0; 1,0; 2,0; 5,0 and 10 cmstandard solution B, which corresponds to 0; 0,1; 0,2; 0,5 and 1,0 mg/lchromium, dilute to the mark with water and mix.

2.4.3. Construction of calibration curve

The solutions comparison is sprayed in the flame acetylene-air, registering the absorbance at the wavelength 357,9 nm all calibration solutions sequentially from smaller to larger contents in reverse order.

According to the obtained values of optical densities and their corresponding concentrations in solutions build a calibration curve in rectangular coordinates. The graph is used for each point the average value of two optical density measurements.

2.5. Analysis

2.5.1. The weight of copper and the capacity of measuring vessels, depending on the mass fraction of chromium is given in table.1.

Table 1

2.5.2. A sample of copper is placed in a beaker with a capacity of 250 cm, pour 20−30 cmof nitric acid (1:1), covered with a cover glass and allowed to stand without heating until the termination of allocation of dinitramide. Then remove the glass, wash it with water above the glass, the solution in the beaker is heated to dissolve the sample.

Pour water to a volume of 200 cmand add 5 cmof sulphuric acid (1:1). The resulting solution is dipped a platinum mesh electrodes and electrolyzed at a current density of 2.0 to 3.0 A/DMand voltage of 2.2−2.5 with stirring. When the solution is colorless, the electrolysis is stopped. The electrodes are removed and washed with water, and the electrolyte is evaporated when heated to dry salts. Then dissolve salt in 3−5 cmof hydrochloric acid (1:1) solution and placed in a measuring tube with a capacity of 10 cm, is diluted to the mark with water and mix.

The obtained solution is sprayed in the enriched air-acetylene flame at the same time with the control solutions and the solutions of the comparison, registering the absorbance at the wavelength 357,9 nm. Measurement conditions selected in accordance with the brand (model) of the used device.

For calibration of the instrument used solutions comparison with a chromium content of 0.1−1.0 mg/DM, using the extension scale on the device itself or of the recorder to him.

2.5.3. After the determination of chromium in the sample solution allowed the determination of cadmium, spraying the solution into the flame of acetylene-air and measuring the absorption of the resonance line of cadmium at a wavelength of 228,8 nm. The mass of cadmium is determined by a calibration schedule in a volumetric flask with a capacity of 100 cmis placed 0; 1,0; 2,0; 5,0; 10,0 solution B and 2, 5, 10 cmsolution A, which corresponds to 0; 0,01; 0,02; 0,05; 0,1; 0,2; 0,5 and 1.0 mg of cadmium. Dilute to the mark with water and mix. The solutions were sprayed in the flame of acetylene-air and measured the absorption line of cadmium at a wavelength of 228,8 nm successively from smaller to larger contents in reverse order. According to the obtained results build a calibration curve in rectangular coordinates.

2.6. Processing of the results

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

,

where is the concentration of chromium in the sample solution, found by calibration schedule, mg/DM;

the concentration of chromium in solution in the reference experiment, mg/DM;

the volumetric capacity of the tube, cm;

 — weight of copper,

2.6.2. Allowable absolute discrepancies in the results of two parallel definitions should not exceed the permissible discrepancy (a measure of convergence), the values of which are given in table.2.

Table 2

Permitted discrepancies for the intermediate mass fraction calculated by linear interpolation.

2.6.3. Discrepancies in the results of the analysis of the same samples obtained in two laboratories and one reference laboratory, but under different conditions should not exceed the permissible discrepancy (a measure of reproducibility) of the two analyses are given in table.2.

2.6.4. Control of the correctness of the results of the analysis carried out using standard samples of composition of copper any category or method of additions of a standard solution of chromium in one of the batches of copper before analysis.

The results of the analysis you think is right, if you played mass fraction of this component in the standard sample differs from the certified characteristics are not more than the value of 0.71, is given in table.2.

When using the method supplements the results of the analysis you think is right, if the found value differs from the additive introduced its value of not more than 0.71, where and  — the permissible discrepancy of the two results of the analysis for the sample and the sample with the additive, respectively.

3. METHODS FOR DETERMINATION OF CADMIUM

3.1. Polarographic method (at a mass fraction of up to 0,0005 0,00002%)

3.1.1. The essence of the method

The method is based on polarography solution containing cadmium, on the background of 1 M potassium chloride, using anodic Stripping voltammetry with the stationary mercury electrode. The potential of the anodic peak minus 0.65 In (relatively saturated calomel electrode).

3.1.2. Equipment, accessories, utensils

Polarograph any brand, provided a reversible linear scanning of the external potential.

The polarographic cell, made of glass (with a capacity of 40 cm), with a stationary drip mercury indicator electrode and a remote reference electrode (saturated calomel or silver-chloride electrodes). Allowed to use a mercury film electrode, prepared as follows: a silver wire soldered to a glass tube, naitanui part of the wire is polished to a Shine with a piece of silver and a polished end placed in a glass of metallic mercury for 1 minute the Amalgamated electrode is removed from the mercury and carefully rubbed with a piece of tracing paper or Teflon for uniform distribution of mercury on the surface of the metal. The electrode, washed thoroughly with water.

Electrolysis installation DC.

Electrodes made of platinum mesh according to GOST 6563.

Volumetric flasks 2−100 (1000)-2 GOST 1770.

A glass according to GOST 19908*.
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* On the territory of the Russian Federation GOST 19908−90.

Glass N-1−250 (400) TC GOST 25336.

Pipette 2−2-10 according to GOST 20292.

Pipette 4−2-1 GOST 20292.

3.1.3. Reagents, solutions

Nitric acid according to GOST 11125 or nitric acid according to GOST 4461 (boiled to remove dinitramide) diluted 1:1.

Sulfuric acid according to GOST 4204, diluted 1:4.

Hydrochloric acid according to GOST 3118.

Ammonia water according to GOST 3760.

Potassium chloride according to GOST 4234, solution 1 mol/DM(1 M).

Nitrogen gas according to GOST 9293.

Mercury metal according to GOST 4658 stamps r0 that does not contain moisture and is cleaned of oxide films in the following manner: 30−50 cmof mercury is transferred from a container into a glass and slowly filtered through a double dry filter medium density, which in the lower part of the filter make a small needle hole. Filtered mercury immediately placed in the pressure capacity of mercury dripping electrode and store in a tightly closed pressure vessel.

Cadmium GOST 1467* brand Кд0.
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* On the territory of the Russian Federation GOST 1467−93. — Note the manufacturer’s database.

Silver GOST 6836* or other regulatory-technical documentation.
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On the territory of the Russian Federation GOST 6836−2002. — Note the manufacturer’s database.

Bidistilled water, prepared according to GOST 4517.

Universal indicator paper.

3.1.4. Preparation for assay

Preparation of standard solutions of cadmium

Solution a: the sample of cadmium with a mass of 0.10 g was placed in a beaker with a capacity of 200 cm, flow 30 cmof nitric acid (1:1) and dissolved by heating prior to the removal of dinitramide. The solution was cooled, poured 50 cmof water, stirred and placed in a measuring flask with volume capacity of 1000 cm, is diluted to the mark with water and mixed again.

1 cmof solution A contains 0.1 mg of cadmium.

Solution B: pipetted 10 cmof solution A and placed in a volumetric flask with a capacity of 100 cm, add 2 cmof hydrochloric acid, dilute to the mark with water and mix.

1 cmof a solution contains 0.01 mg of cadmium.

Solution: pipetted 10 cmof a solution and placed in a volumetric flask with a capacity of 100 cm, add 2 cmof hydrochloric acid, dilute to the mark with water and mix; prepared immediately before analysis;

1 cmof the solution contains 0.001 mg of cadmium.

3.1.5. Analysis

A sample of copper with a mass of 1.00 g were placed in a glass made of quartz glass with a capacity of 200 cm, add 15 cmof nitric acid, cover the beaker glass (cap) and dissolve when heated. After dissolution, the sample solution was boiled for 2−3 min to remove dinitramide, cooled, diluted with water to a volume of 150 centimeters, add 7 cmof sulfuric acid and conduct electrolysis at a current density of 2−3 A/DMand voltage of 2.2−2.5 with stirring. When the solution is colorless, the electrolysis is stopped. The electrodes are removed and washed with water on the glass, and electrolyte is evaporated when heated to wet salts. Then dissolve salt in 3−5 cmof hydrochloric acid (1:1) and add 15 cmof potassium chloride solution, stirred to dissolve the salts and ammonia establish a pH value of~4.5 to 5 (universal indicator paper). The solution is transferred into a polarographic cell, is passed through a solution of nitrogen for 10 min, and then mounted on polarography voltage 1.1 V and the electrolysis is carried out for 5−10 min with continuous stirring of the solution with nitrogen or agitator.

After the time of the electrolysis, the mixing is stopped, allow the grout to settle down with 10−20 and remove polarogram anodic dissolution at linear change of voltage, recording at minus 0.65 In peak anodic dissolution of the cadmium.

The time of electrolysis and the sensitivity of the device is chosen so that the height of the recorded peak was at least 10 mm.

Repeat the electrolytic process of accumulation of cadmium and voltamperometry, as stated above, using a new mercury drop electrode or mercury film cleaning electrode (the electrode is kept at a voltage of 0.05 V for 1 min in the continuously stirred solution, and then repeat the measurement).

For the height of the anodic peak of cadmium in the analyzed samples take the average of two consecutive measurements.

Determination of cadmium is carried out by additives, which in the analyzed solution in the cell, add 0.2−0.5 cmof the respective standard solution of cadmium. The value of the Supplement and concentration of a standard solution is chosen so that the peak height of the cadmium after the measurement of additive increased in 2−2,5 times.

The solution was stirred with nitrogen for 1−2 min and then spend the measurement, as in the determination of cadmium in the sample solution.

Simultaneously with the analysed solution is performed the measurement of the solution in the reference experiment.

3.1.6. Processing of the results

3.1.6.1. Mass fraction of cadmium (a) in percent is calculated by the formula

,

where the cadmium concentration in the standard solution, mg/cm;

 — height of the anodic peak of cadmium in solution in the reference experiment, mm.

 — height of the anodic peak of cadmium in solution of the sample, mm;

 — height of the anodic peak of cadmium after the introduction of additives to the sample solution, mm;

 — the volume of the additive standard solution of cadmium, cm;

 — weight of copper,

3.1.6.2. Allowable absolute discrepancies in the results of two parallel definitions should not exceed the permissible discrepancy (a measure of convergence), the values of which are given in table.3.

Table 3

Permitted discrepancies for the intermediate mass fraction calculated by linear interpolation.

3.1.6.3. Discrepancies in the results of the analysis of the same samples obtained in two laboratories and one reference laboratory, but under different conditions should not exceed the permissible discrepancy (a measure of reproducibility) of the two analyses are given in table.3.

3.1.6.4. Control of the correctness of the analysis results according to claim 2.6.4.

3.2. Atomic absorption method (with a mass fraction of 0.0005 to 0.00005%)

3.2.1. The essence of the method

The method is based on measurement of the absorption resonance line of cadmium at a wavelength of 228,8 nm with the introduction of the analyzed solution into air-acetylene flame.

3.2.2. Equipment, accessories, utensils

Atomic absorption spectrophotometer of any type

Lamp with hollow cathode for cadmium or electrodeless discharge lamp.

Air compressor.

Acetylene according to GOST 5457.

Glass high (or low) with a capacity of 100 cmaccording to GOST 25336.

Volumetric flasks with a capacity of 100 and 1000 cmaccording to GOST 1770.

Pipette 2−2-10, 2−2-20, 7−2-5, 7−2-10 according to GOST 20292.

3.2.3. Reagents and solutions

Nitric acid of high purity according to GOST 11125 or nitric acid according to GOST 4461, diluted 1:1.

Copper according to GOST 859, a solution of 20 g/DM: a sample of copper with a mass of 2.00 g was dissolved with heating in 15−20 cmof nitric acid to remove dinitramide. Cool and place the solution in a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

Cadmium GOST 1467 brand Кд0.

3.2.4. Preparation for assay

3.2.4.1. Preparation of standard solutions of cadmium

Solution a: the sample of cadmium with a mass of 1.00 g is dissolved in 15 cmof nitric acid and 10 cmof water under heating, to dissolve the attachment and removal of nitrogen oxides. Then the solution is placed in a measuring flask with volume capacity of 1000 cm, is diluted to the mark with water and mix.

1 cmof the solution contains 1 mg of cadmium.

Solution B: pipetted 5 cmof solution A and placed in a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

1 cmof the solution contains 0.05 mg of cadmium.

Solution: pipetted 10 cmof a solution and placed in a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

1 cmof the solution contains 0.005 mg of cadmium.

3.2.4.2. Construction of calibration curve

In a volumetric flask with a capacity of 100 cmplaced: 0; 0,5; 1,0; 3,0; 5,0; 10 cmstandard solution, which corresponds to 0; 0,002; 0,005; 0,015; 0,025; 0,050 mg of cadmium. Pour 50 cmof copper solution, dilute to the mark with water and mix. Calibration solutions sprayed in the flame acetylene-air, recording the absorption line of cadmium at a wavelength of 228,8 nm, successively from smaller to larger contents in reverse order.

According to the obtained values of optical densities and corresponding concentrations of cadmium in the calibration solutions to build a graph in rectangular coordinates. The graph is used for each point the average value of two optical density measurements.

3.2.5. Analysis

A sample of copper with a mass of 1.00 g is placed in a beaker with a capacity of 100 cm, 10−15 cm pour thenitric acid and be left without heating until the termination of allocation of dinitramide. The solution was then heated to dissolve the sample, add 30−50 cmof water and place the resulting solution in a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

Spray the solution into the flame of acetylene-air and measured the absorption line of cadmium at a wavelength of 228,8 nm.

The mass of cadmium is determined according to the calibration schedule.

Measurement conditions selected in accordance with device used.

3.2.6. Processing of the results

3.2.6.1. Mass fraction of cadmium (a) in percent is calculated by the formula

,

where is the mass of cadmium was found in the calibration schedule, mg/DM;

 — weight of copper,

3.2.6.2. Discrepancies in the results of two parallel measurements and the two tests are given in table.2.

3.2.6.3. Control of the correctness of the analysis results according to claim 2.6.4.