GOST 25284.2-95

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  ГОСТ 25284.2-95

GOST 25284.2−95 Alloy zinc. Methods for determination of copper

GOST 25284.2−95

Group B59

INTERSTATE STANDARD

ZINC ALLOYS

Methods for determination of copper

Zinc alloys. Methods for determination of copper

ISS 71.040.40*
AXTU 1709

____________________
* In the index «National standards», 2008
ISS 77.120.60. — Note the manufacturer’s database.

Date of introduction 1998−01−01

Preface

1 DEVELOPED by the Donetsk state Institute of non-ferrous metals (Danism); International technical Committee MTC 107

SUBMITTED to the State Committee of Ukraine for standardization, Metrology and certification

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (EASC Protocol No. 7 of April 26, 1995)

The adoption voted:

3 Resolution of the State Committee of the Russian Federation for standardization, Metrology and certification dated June 2, 1997 N 204 inter-state standard GOST 25284.2−95 was put into effect directly as the state standard of the Russian Federation from January 1, 1998

4 REPLACE GOST 25284.2−82

1 SCOPE

This standard applies to zinc alloys, and sets the atomic absorption (at a mass fraction of copper from 0.005 to 8%), iodometric and electrogravimetry (with mass fraction of copper from 0.5 to 6%) methods for determination of copper in samples of these alloys.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 83−79 Sodium carbonate. Specifications

GOST 859−78* Copper. Brand
________________
* On the territory of the Russian Federation GOST 859−2001. Here and further. — Note the manufacturer’s database.

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4232−74 Potassium iodide. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 6691−77 Urea. Specifications

GOST 10163−76 Starch soluble. Specifications

GOST 10929−76 Hydrogen peroxide. Specifications

GOST 18300−87 ethyl rectified technical. Specifications

GOST 25284.0−95 Alloy zinc. General requirements for methods of analysis

GOST 27068−86 Chernovetskiy Sodium (sodium thiosulfate) 5-water. Specifications

3 GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 25284.0.

4 ATOMIC ABSORPTION METHOD

4.1 the essence of the method

The method is based on dissolving the sample in hydrochloric acid and measuring the atomic absorption of copper at a wavelength of 324,7 nm in the flame acetylene-air.

4.2 Equipment, reagents and solutions

Atomic absorption spectrophotometer.

Hydrochloric acid according to GOST 3118, solutions of 1:1 and 2 mol/DM.

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

Hydrogen peroxide according to GOST 10929.

Copper metal according to GOST 859.

Standard solutions of copper

Solution a: 0.5 g of copper is dissolved in 10 cmof nitric acid solution, is removed by boiling oxides of nitrogen, the solution was 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 0.001 g of copper.

Solution B: 25 cmsolution And transferred to a volumetric flask with a capacity of 250 cm, adding 25 cmof a solution (2 mol DM) hydrochloric acid, made up to the mark with water and mix.

1 cmof a solution contains 0.0001 g IU

di.

4.3 analysis

4.3.1 the sample of alloy weighing 1 g is placed in a beaker with a capacity of 200 cmand dissolved in 10 cmof hydrochloric acid (1:1). After dissolution of the sample add 1 cmof hydrogen peroxide and boil for 5 minutes the Solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix. When the mass fraction of copper in excess of 0.1% of selected aliquot part of the solution in accordance with table 1, add 20 cmsolution (2 mol DM) hydrochloric acid, made up to the mark with water and mix.

Table 1

4.3.2 For the construction of calibration curve in six of the seven volumetric flasks with a capacity of 100 cmeach administered 0.5; 2,0; 4,0; 6,0; 8,0 and 10,0 cmof solution B. to all flasks add 10 cmsolution (2 mol DM) hydrochloric acid, made up to the mark with water and mix. The solution to which is not added standard solution B is a solution of the reference experiment.

4.3.3 sample Solution, solution control experience and solutions to build the calibration curve is sprayed into the flame of acetylene-air and measure the atomic absorption at a wavelength of 324,7 nm. According to the obtained values of atomic absorption of copper in the solutions for constructing the calibration curve and their corresponding values of mass concentration to build a calibration curve.

Mass concentration of copper in the sample solution and the solution of control and experience determined by the calibration schedule.

4.4 Processing of results

4.4.1 Mass fraction of copper , %, is calculated by the formula

, (1)

where is the mass concentration of copper in sample solution, g/cm;

mass concentration of copper in solution in the reference experiment, g/cm;

 — the volume of sample solution prepared for the measurement of atomic absorption, cm;

 — the weight of the portion of sample or the mass of the sample in aliquote part of the sample solution,

4.4.2 Discrepancy between the results of parallel measurements and the results of the analysis shall not exceed allowable (at confidence probability of 0.95) of the values given in table 2.

Table 2

Percentage

5 IODOMETRIC METHOD

5.1 the essence of the method

The method is based on dissolving the sample in nitric acid, the oxidation-recovery of divalent copper ions and potassium iodide. Released with the free iodine titrated in the presence of starch solution sodium thiosulfate, which restores it to Lodigiano. Interfering with the action of nitric oxide eliminate urea.

5.2 Reagents and solutions

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

Potassium iodide according to GOST 4232, a solution of 200 g/DM.

Urea according to GOST 6691, saturated solution: 100 g of urea dissolved in 100 cmof hot water.

The soluble starch according to GOST 10163, a solution of 10 g/DM, freshly prepared: 1 g of starch stir in a small amount of water and the resulting suspension is slowly poured into 100 cmof boiling water. Boil until the enlightenment of the solution, is cooled.

Copper metal according to GOST 859.

A standard solution of copper

A sample of copper of mass 1 g is dissolved in 20 cmof nitric acid (1:1), 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 0.002 g of copper.

Sodium carbonate according to GOST 83.

Sodium thiosulfate 5-water according to GOST 27068, solution 0,1 mol/DM: 24.8 g of sodium thiosulfate 5-water is dissolved in water, add 3 g of anhydrous sodium carbonate to the stability of the solution, the solution transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix. The solution is allowed to stand for two weeks in a dark place, and then set the mass concentration of the solution. Store in a container made of dark glass.

To establish the mass concentration of the sodium thiosulfate 25 cmstandard solution of copper is placed in a conical flask with a capacity of 250 cm, add 20 cmof nitric acid, diluted 1:1, heated and further act as specified in 5.3.

The mass concentration of sodium thiosulfate on copper is calculated by the formula

, (2)

where is the mass of copper in aliquotes part of a standard solution of copper (i.e., 25 cm), g;

 — the volume of sodium thiosulfate consumed in the titration, sm.

5.2.1 allowed to set, the mass concentration in the standard sample zinc alloy. In this case, the conical flask was placed a weighed standard sample weight of 2 g and dissolved in 20 cmof nitric acid (1:1) at first the cold and then when heated, then come, as specified in 5.3.

5.3 analysis

A portion of the alloy weight 2 g (for alloys with a mass fraction of copper not more than 2%) and 1 g (for alloys with a mass fraction of copper of more than 2%) is placed in a conical flask with a capacity of 250 cm, and dissolved in 20 cmof nitric acid (1:1) at first the cold and then when heated. After dissolve and remove oxides of nitrogen by boiling, add 1 cmof a solution of urea to bind the residual nitrogen oxides, the walls of the flask is washed with water, add 80−100 cmof water, 20 cmof a solution of potassium iodide, incubated 3−5 minutes, titrated with sodium thiosulfate to a straw yellow color, add 5 cmof starch and continue titration to the disappearance of the blue color of the solution. The sodium thiosulfate at the end of the titration, add drop by drop, carefully stirring the contents of the flask after adding each drop.

5.4 processing of the results

5.4.1 Mass fraction of copper , %, is calculated by the formula

, (3)

where is the volume of sodium thiosulfate consumed in the titration, cm;

 — mass concentration of sodium thiosulfate expressed in grams of copper per 1 cmof the solution in g/cm;

 — the weight of the portion of the sample,

5.4.2 Discrepancy between the results of parallel measurements and the results of the analysis shall not exceed allowable (at confidence probability of 0.95) of the values given in table 2.

6 ELECTROGRAVIMETRY METHOD

6.1 the essence of the method

The method is based on dissolving the sample in nitric acid, the electrolytic release of copper from a solution of nitric acid and sulfuric acid and to establish its mass.

6.2 Apparatus, reagents and solutions

Installation for electrolysis.

Stirrer (mechanical or magnetic) or a rotating anode.

The electrodes are platinum mesh or hardened platinum alloys with metals of the same group.

Nitric acid according to GOST 4461 diluted 1:99.

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

Ammonia water according to GOST 3760.

Ethanol technical rectified according to GOST 18300.

6.3 analysis

A sample of alloy weighing 5 g were placed in a glass with a capacity of 400−600 cm, add 20 cmof water. Cover the watch glass and carefully in small portions add 20 cmof nitric acid.

When the violent reaction dissolving, the beaker was cooled with water. After the end of the dissolution process remove watch glass by rinsing it and the side of the Cup with water, then remove the oxides of nitrogen by boiling and topped up to 200 cmwater. To the solution with constant stirring, add dropwise ammonia until the appearance of turbidity due to the formation of aluminum hydroxide, add 2 cmof nitric acid, 4 cmof sulfuric acid solution and add water up to 300 cm. Pre-weigh the cathode, cleaned in nitric acid, washed in ethanol and dried at a temperature of 105−110 °C for 3−5 min. Insert electrodes into the cell, set the glass with the solution in the desired position and add water to complete immersion of the electrodes. Serves a corresponding detachable lid or the two halves of the hour glass and conduct electrolysis at a current density of 2 A/DMand stirring the solution. After 30 minutes wash the cover and sides of beaker with water and continue electrolysis until then, until the deposition of copper, as evidenced by the absence of sediment on svezheokrashennoj surface of the cathode. Reduce the current density to 0.5 A/DMand washed electrodes, immersing them first in a glass with a solution of nitric acid (1:99) and then with water. Without turning off the current, remove the cathode from the solution, rinsed with water and after the current is switched off washed with ethanol. The cathode is dried for 5−10 minutes at a temperature of 105−110 °C, cooled and vzveshivat

yut.

6.4 Processing of results

6.4.1 Mass fraction of copper , %, is calculated by the formula

, (4)

where is the mass of sample, g;

 — the mass of cathode, g;

 — the mass of the cathode with segregated copper,

6.4.2 divergence of the results of parallel measurements and the results of the analysis shall not exceed allowable (at confidence probability of 0.95) of the values given in table 2.