GOST 25284.5-95

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  ГОСТ 25284.5-95

GOST 25284.5−95 Alloy zinc. Methods for determination of cadmium

GOST 25284.5−95

Group B59

INTERSTATE STANDARD

ZINC ALLOYS

Methods for determination of cadmium

Zinc alloys. Methods for determination of cadmium

ISS 71.040.40*
AXTU 1709
____________________
* In the index «National standards» in 2007.
ISS 71.120.60. — 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 25284.5−95 was put into effect directly as the state standard of the Russian Federation from January 1, 1998

4 REPLACE GOST 25284.5−82

1 SCOPE

This standard applies to zinc alloys, and sets the atomic absorption, polarographic and chelatometric methods for the determination of cadmium with mass fraction of from 0.001 to 0.03% in the samples of these alloys.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 1467−93 Cadmium. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 4160−74 Potassium bromide. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 9293−74 Nitrogen gaseous and liquid. Specifications

GOST 10652−73 Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid 2-water (Trilon B)

GOST 10929−76 Hydrogen peroxide. Specifications

GOST 18300−87 ethyl rectified technical. Specifications

GOST 20015−88 Chloroform. Specifications

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

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 cadmium in the flame acetylene-air at a wavelength of 228,8 nm.

4.2 Equipment, reagents and solutions

Atomic absorption spectrophotometer.

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

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

Hydrogen peroxide according to GOST 10929.

Cadmium metal according to GOST 1467.

Standard solutions of cadmium

Solution a: 0.5 g of cadmium dissolved in 20 cmof a solution of nitric acid, cooled, 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 cadmium.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, add 10 cmsolution (2 mol DM) hydrochloric acid, made up to the mark with water and mix.

1 cmof a solution contains 0.0001 g of cadmium.

Solution: 10 cmof solution B is placed in a volumetric flask with a capacity of 100 cm, add 10 cmsolution (2 mol DM) hydrochloric acid, made up to the mark with water and mix.

1 cmof the solution contains 0,00001 g

cadmium.

4.3 analysis

4.3.1 the sample of alloy weighing 1 g is placed in a beaker with a capacity of 300 cm, add 10 cmof hydrochloric acid solution, diluted 1:1. After termination of the reaction dissolved add 1 cmof hydrogen peroxide and boil for 5 minutes the Solution was cooled, transferred to a volumetric flask with a capacity of 50 cm, made up to the mark with water and mix.

4.3.2 for the mass concentration of cadmium above 0.01% of the solution obtained in accordance with 4.3.1, select aliquot part of 25 cm, placed in a volumetric flask with a capacity of 50 cm, made up to the mark with water and mix.

4.3.3 For constructing a calibration curve in six of the seven volumetric flasks with a capacity of 50 cmeach introduce 1,0; 3,0; 6,0; 9,0; 12,0 and 15,0 cmV. standard solution To each flask add 5 cmsolution (2 mol DM) hydrochloric acid, made up to the mark with water and mix. The solution to which is not added to the cadmium, is a solution of the reference experiment.

4.3.4. Solutions of the samples obtained in accordance with 4.3.1 and 4.3.2, control, experience and solutions to build the calibration curve is sprayed into the flame of acetylene-air and measure the atomic absorption of cadmium at a wavelength of 228,8 nm.

According to the obtained values of atomic absorption and corresponding values of mass concentration to build a calibration curve in the coordinates: the value of atomic absorption — mass concentration, g/cm.

Mass concentration of cadmium 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 cadmium , %, is calculated by the formula

, (1)

where is the mass concentration of cadmium in the sample solution found by the calibration schedule, g/cm;

 — mass concentration of cadmium in solution in the reference experiment, was found in the calibration schedule, g/cm;

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

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

.

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 1.


Table 1

Percentage

5 CHELATOMETRIC METHOD

5.1 the essence of the method

The method is based on dissolving the alloy in sulfuric acid solution, the separation of cadmium from other interfering components in the form tetrabranchiata diantipyrylmethane and titration of cadmium disodium salt of ethylenediaminetetraacetic acid in the presence of acid chrome dark blue.

5.2 Reagents and solutions

Sulfuric acid according to GOST 4204, diluted 1:6, and a solution of 0.05 mol/DM.

Diantipyrylmethane in the normative documentation.

Potassium bromide according to GOST 4160, a solution of 100 g/DM.

Hydrochloric acid according to GOST 3118.

Nitric acid according to GOST 4461.

Ammonia water according to GOST 3760, a solution of 2:3.

The washing liquid I containing 10 cmof sulphuric acid, 20 g of potassium bromide and 10 g diantipyrylmethane in 1 DMof water.

The washing liquid II containing 10 cmof hydrochloric acid, 5 g of potassium bromide and 3 g diantipyrylmethane in 1 DMof water.

Cadmium GOST 1467.

A standard solution of cadmium

0,2248 g powdered cadmium dissolved in 20 cmof sulphuric acid with the addition of a few drops of nitric acid, evaporated to fumes of sulfur oxide (IV), cool, dissolve the residue in water, transferred to a volumetric flask with a capacity of 1 DM, adjusted to the mark with water and mix.

1 cmof the solution contains 0,0002248 g of cadmium.

Acid chrome dark blue in the standard documentation, a solution of 5 g/DM.

Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid 2-water (Trilon B) according to GOST 10652, a solution of 0.002 mol/DM: 7.44 grams of salt dissolve in water, transfer the solution into a volumetric flask with a capacity of 1 DM, adjusted to the mark with water and mix. Then 100 cmof the resulting solution Trilon B, is placed in a volumetric flask with a capacity of 1 DM, adjusted to the mark with water and mix.

To establish the mass concentration of the solution Trilon B 20 cmstandard solution of cadmium was placed in a conical flask, add 100 cmof water, set pH 10 with ammonia, add 3 drops of acid chrome dark blue and titrate with a solution of Trilon B before moving on pink coloring in blue and purple.

Mass concentration of Trilon B, expressed in grams of cadmium in 1 cmof a solution, calculated by the formula

, (2)

where is the mass concentration of cadmium standard solution, g/cm;

 — volume (20 cm) of a standard solution of cadmium, cm;

 — volume of solution Trilon B, used for titration, see

.

5.3 analysis

A sample of alloy weighing 10 g was dissolved in 50 cmof sulfuric acid solution (1:6) first on the cold and then when heated. Spongy undissolved copper was filtered through a filter medium density («white ribbon»). The filter cake was washed 3−4 times with hot water. The filtrate and washings, which should not exceed 70−80 cm, heated to boiling, add 0.5 g diantipyrylmethane, after dissolution which add 20 cmpreheated to 70 °C solution of potassium bromide and left for 3−4 h for the deposition of complex compounds of cadmium.

A precipitate of brilliant silky needles, is filtered through two medium density filter and periostat for a more complete separation of the zinc salts. To do this, dissolve the precipitate on the filter with hot solution (0.05 mol/DM) of sulfuric acid, collect the solution in the beaker, which conducted the deposition, heat the solution to boiling, add 0.5 g diantipyrylmethane, 15 cmof hot solution of potassium bromide and allowed to stand overnight. The precipitate was filtered off through a double filter medium density, washed the beaker and the residue on the filter 4−5 times (3−4 cm) of the rinsing liquid I and then 2 times washed with liquid II.

The precipitate is dissolved on the filter with 50 cmof ammonia solution (2:3) collect the solution in a conical flask with a capacity of 250 cm, heated to boiling, wash the walls of the flask with water, add 3−4 drops of acid chrome dark blue and titrate with a solution of Trilon B before moving on pink coloring in blue and purple.

For the mass concentration of cadmium is less than 0.02% for titration use microbiuret

.

5.4 processing of the results

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

, (3)

where is the mass concentration of Trilon B, expressed in grams of cadmium in a 1 cmsolution, g/cm;

 — volume of solution Trilon B, used for titration of the sample solution, 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 1.

6 POLAROGRAPHIC METHOD

6.1 the essence of the method

The method is based on dissolving the samples in hydrochloric acid, separation of copper with salicylaldoxime and polarographic determination of cadmium in the range of potentials from minus 0.5 to minus 0.9 volts relative to a saturated calomel electrode.

6.2 Apparatus, reagents and solutions

Polarograph.

Hydrochloric acid according to GOST 3118, a solution of 1:1.

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

Hydrogen peroxide according to GOST 10929.

Potassium perchlorate according to the normative documentation, solution, saturated at room temperature.

Ethanol technical rectified — GOST 18300.

Salicylaldoxime in the normative documentation, solution: 4 g salicylaldoxime dissolved in 40 cmethanol and stirring, add 50 cmof water, heated to 80 °C.

Irrigation solution: 5 cmsalicylaldoxime solution is diluted with water to a volume of 1 DM.

Chloroform according to GOST 20015.

Nitrogen gas according to GOST 9293.

Cadmium metal according to GOST 1467.

Standard solutions of cadmium

Solution a: prepared in accordance with 4.2.

1 cmof the solution contains 0.001 g of cadmium.

Solution B: 10 cmsolution And transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.0001 g of cadmium

I.

6.3 analysis

A sample of alloy weighing 5 g were placed in a glass with a capacity of 600 cmand dissolved in 50 cmof hydrochloric acid. After dissolution, add 5 cmof hydrogen peroxide and evaporated to a syrupy condition.

When the mass fraction of copper to 0.05% add 5 cmof water, shake until dissolved salts, transferred to a volumetric flask with a capacity of 25 cm, top up to the mark with water and mix. When the mass fraction of copper in excess of 0.05% add 125 CCof water and heated until complete dissolution of salts. Depending on the mass fraction of copper added 10−15 cmof the solution salicylaldoxime and leave for 30 minutes, occasionally stirring the solution.

The precipitate was filtered and washed several times with irrigation solution. The filtrate is evaporated to a volume of 30 cm, transferred to a separatory funnel with a capacity of 100 cm, washing out a glass of 20 cmof water, and extracted twice by adding 25 cmof chloroform each time and shaking for 1 min. the Organic layer is discarded and the aqueous layer was transferred to a beaker with a capacity of 100 cmand evaporated to a syrupy condition. Add 2.5 cmof a solution of potassium perchlorate, a glass cover watch glass and evaporated to a syrupy condition. Add another 2.5 cmof potassium perchlorate and again evaporated to a syrupy condition. Then remove the watch glass, rinse it with water, add 5 cmof hydrochloric acid and evaporated to syrupy state. Again add 5 cmof hydrochloric acid and repeat the evaporation. Add 5 cmof water, shake until dissolved, transferred to a volumetric flask with a capacity of 25 cm, top up to the mark with water and mix.

Part of the solution is transferred into a cell of polarography, was purged with nitrogen for 10 min and record the wave in the range of potentials from minus 0.5 to minus 0.9 V relative to the calomel electrode. At the same time the analysis of the sample by adding to the solution a volume of a standard solution to the wave height corresponding to this additive (), was in the range of 0.8−1.2 wave height analyses

sponsored sample.

6.4 Processing of results

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

, (4)

where  — height of a wave of cadmium in the sample solution, mm;

 — the height of a wave of cadmium in the sample solution with the addition of a standard solution, mm;

 — supplements weight of cadmium, g;

 — the weight of the portion of the sample,

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 1.