GOST 25284.3-95

• gost-252843-95.pdf (358.98 KiB)
  ГОСТ 25284.3-95

GOST 25284.3−95 Alloy zinc. Methods for determination of magnesium

GOST 25284.3−95

Group B59

INTERSTATE STANDARD

ZINC ALLOYS

Methods for determination of magnesium

Zinc alloys. Methods for determination of magnesium

ISS 71.040.40*
AXTU 1709
____________________
* In the index «National standards» 2007
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 25284.3−95 was put into effect directly as the state standard of the Russian Federation from January 1, 1998

4 REPLACE GOST 25284.3−82

1 SCOPE

This standard applies to zinc alloys, and sets the atomic absorption (at a mass fraction of magnesium of from 0.005 to 0.1%) and chelatometric (with mass fraction of magnesium from 0.01 to 0.1%, and from 0.03 to 0.06%) methods for determination of magnesium in samples of these alloys.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 804−93 primary Magnesium ingots. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3773−72 Ammonium chloride. Specifications

GOST 4147−74 Iron (III) chloride 6-water. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4217−77 Potassium nitrate. Specifications

GOST 4233−77 Sodium chloride. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 8465−79 Potassium cyanide technical. Specifications

GOST 8864−71 Sodium N, N-diethyldithiocarbamate 3-water. 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 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 magnesium in the flame acetylene-air or acetylene-nitrogen dioxide at a wavelength of 285,21 nm.

4.2 Equipment, reagents and solutions

Atomic absorption spectrophotometer.

Nitric acid according to GOST 4461.

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

Hydrogen peroxide according to GOST 10929.

Lanthanum oxide or lanthanum nitrate in the normative documentation.

Lanthanum, a solution of 60 g/DM.

A portion of the lanthanum oxide by weight of 7 g of nitrate or lanthanum with a mass of 18.7 g dissolved in water with addition of 5 cmof nitric acid, the solution transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Magnesium metal according to GOST 804.

Water bidistilled.

Standard solutions of magnesium

Solution a: 0.5 g of magnesium is placed in a beaker with a capacity of 250 cmadd 30 cmwater and 25 cmof a solution of hydrochloric acid (1:1), the resulting solution of magnesium 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 0.0005 g of magnesium.

Solution B: 10 cmsolution And transferred to 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 solution B contains 0,00005 g

magnesium.

4.3 analysis

4.3.1 the sample of alloy weighing 1 g is placed in a beaker with a capacity of 400 cm, and dissolved in 10 cmof hydrochloric acid (1:1). At the end of the violent reaction of the dissolution add 5 cmof hydrogen peroxide and boil for 5 minutes the Solution was cooled.

4.3.2 for the mass concentration of magnesium, less than 0.02% solution transferred to a volumetric flask with a capacity of 100 cm, flow 20 cmof a solution of lanthanum, made up to the mark with water and mix.

4.3.3 When the mass fraction of magnesium in excess of 0.02% solution transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

20 cmresulting solution was placed in a volumetric flask with a capacity of 100 cm, add 20 cmof a solution of lanthanum and 10 cmsolution (2 mol DM) hydrochloric acid, made up to the mark with water and mix.

4.3.4 To build a calibration curve in five out of six volumetric flasks with a capacity of 100 cmeach placed 1,0; 2,0; 3,0; 4,0; 5,0 cmstandard solution B. In each flask add 10 cmof solution (2 mol DM) hydrochloric acid, made up to the mark with water and mix. The solution, in which magnesium is not entered, is the solution of the reference experiment.

4.3.5 Solutions of the samples in the reference experiment and the solutions for constructing the calibration curve is sprayed into the flame of acetylene-air or acetylene-nitrogen dioxide and measured by atomic absorption at a wavelength of 285,21 nm.

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

Mass concentration of magnesium 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 magnesium in % is calculated by the formula

, (1)

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

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

 — the volume of the sample solution, cm;

 — the weight of the portion of sample or the mass of the sample in the appropriate 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 WITH the chelating agent IV (WITH MASS FRACTION of MAGNESIUM FROM 0.01 to 0.1%)

5.1 the essence of the method

The method is based on dissolving the sample in a mixture of hydrochloric and nitric acids, separation of the magnesium with the use of iron (III) hydroxide and complexometric titration with a solution cyclohexane-1,2-diaminetetraacetic acid (a chelating agent IV).

5.2 Reagents and solutions

Hydrochloric acid according to GOST 3118, diluted 1:5 and 1:1.

Nitric acid according to GOST 4461.

Ammonia water according to GOST 3760.

Sodium hydroxide according to GOST 4328, solutions of 400 g/land 40 g/DM, freshly prepared.

Hydrogen peroxide according to GOST 10929, diluted 1:10.

Potassium cyanide according to GOST 8465, a solution of 250 g/DM, freshly prepared, or Tetraethylenepentamine (tetraen) by the regulatory documents, diluted 1:3.

Iron (III) chloride 6-water according to GOST 4147, solution: 35 g of reagent was dissolved in 25 cmof hydrochloric acid and add water to 1 DM.

Potassium nitrate according to GOST 4217.

Methylene blue, a solid mixture of: 0.1 g of methyl blue triturated with 10 g of potassium nitrate.

Magnesium metal according to GOST 804.

Standard solutions of magnesium

Solution a: 1 g of magnesium was placed in a beaker with a capacity of 100 cm, add 30 cmwater and 25 cmof hydrochloric acid diluted 1:1. The solution was cooled and transferred to volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof the solution contains 0.001 g of magnesium.

Solution B: 25 cmsolution And placed in a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.0001 g of magnesium.

Acid cyclohexane-1,2-diaminetetraacetate (IV chelating agent), a solution of 0.01 mol/DM: 3,64 g of IV chelating agent dissolved in 100 cmof water containing 20 cmof solution (40 g/DM) of sodium hydroxide. The solution was transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

The mass concentration of chelating agent IV set as follows: 20 cmstandard solution B is placed in a beaker with a capacity of 600 cm, add 10 cmof hydrochloric acid, 250 cmof water 100 cmof ammonia, a solid mixture of the indicator on the spatula tip (about 0.1 g) and titrated with a solution of chelating agent IV until the disappearance of blue color.

At the same time under the same conditions conduct control experience without the use of a standard solution of magnesium.

Mass concentration (g/cm) solution of the chelating agent IV, expressed in grams of magnesium per 1 cmof a solution, calculated by the formula

, (2)

where is the mass of magnesium contained in 20 cmstandard solution, g;

the volume of the solution of chelating agent IV, used for titration of standard solution of magnesium, cm;

the volume of the solution of chelating agent IV, used for titration of the solution in the reference experiment, cm.

5.3 analysis

5.3.1 a sample of alloy weighing 5 g were placed in a glass with a capacity of 600 cm, add 20 cmof hydrochloric acid. After termination of the reaction the dissolution add 5 cmof nitric acid and boiled for 10 min.

5.3.2 To the solution add 2cmof a solution of ferric chloride in small portions, 100 cmsolution (400 g/DM) of sodium hydroxide, stirring thoroughly. Continuing to mix, add 5 cmof a solution of cyanide of potassium, or 20 cmsolution TERENA and 150 cmof water. Bring the solution to boiling and keep hot for 30 minutes to coagulate the hydroxides of iron and magnesium.

Solution and the precipitate was filtered through a dense filter of «blue ribbon», the filter cake and the side of the Cup, which led the precipitation, washed with hot solution (40 g/cm) of sodium hydroxide and then twice with hot water.

The filter cake is dissolved in 40 cmof hot hydrochloric acid (1:5). The filter is washed with 100 cmof hot water, collecting the solution and washings into the beaker, which conducted the deposition.

To the solution was added 1 cmof hydrogen peroxide and ammonia dropwise until then, until the precipitation of iron hydroxide, and 4 to 5 drops in excess.

The solution was heated to reflux and heating was continued for another 5 min. the Precipitate was filtered, collecting the filtrate in a beaker with a capacity of 600 cm, and washed 5 times with hot water.

The filtrate is cooled, add 100 cmof ammonia, 4 cmof a solution of cyanide of potassium, or 15 cmof the solution tetraena, solid mixture of the indicator at the tip of a spatula and titrated with a solution of chelating agent IV until the disappearance of blue

color.

5.3.3 Simultaneously with the sample analysis spend control experience. To do this in a glass with a capacity of 400 cm, covered with a watch glass, placed 20 cmof hydrochloric acid and 5 cmof nitric acid. Boil for 10 minutes and come on as shown in 5.3.2.

5.4 processing of the results

5.4.1 Mass fraction of magnesium in % is calculated by the formula

, (3)

where  — volume of the solution of chelating agent IV consumed for titration of sample solution, cm;

the volume of the solution of chelating agent IV, used for titration of the solution in the reference experiment, cm;

 — mass concentration of the chelating agent IV, expressed in grams of magnesium per 1 cmof the solution in g/cm;

 — the weight of the portion of the sample,

G.

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 CHELATOMETRIC METHOD WITH SODIUM DIETHYLDITHIOCARBAMATE (with mass fraction of magnesium from 0.03 to 0.06%)

6.1 the essence of the method

The method is based on complexometric titration of magnesium with Trilon B in an alkaline medium with a preliminary separation of interfering components.

6.2 Reagents and solutions

Sulfuric acid according to GOST 4204, diluted 1:9.

Hydrochloric acid according to GOST 3118, diluted 1:1 and 1:4.

Sodium hydroxide according to GOST 4328, solutions of 300 g/land 20 g/l, freshly prepared.

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

Iron (III) chloride 6-water according to GOST 4147, solution: 25 g of reagent was dissolved in 25 cmof hydrochloric acid and add water to 1 DM.

Ammonium chloride according to GOST 3773, solution 100 g/DM.

Sodium chloride according to GOST 4233.

Eriochrome black T.

Display a mixture of: 0.1 g of the indicator eriochrome black T triturated with 10 g of sodium chloride.

Buffer solution pH 10: 70 g ammonium chloride dissolved in approximately 150 cmof water, transferred to a volumetric flask with a capacity of 1 DM, made up of 750 cmof ammonia, made up to the mark with water and mix. The solution was stored in a plastic container.

Sodium diethyldithiocarbamate according to GOST 8864, solution 100 g/DM.

Universal indicator paper.

Magnesium metal with purity not less than 99.99% according to GOST 804.

Standard solution of magnesium, 1 g of magnesium is placed in a tall glass with a capacity of 400 cm, add about 200 cmof water and 30 cmof a hydrochloric acid solution (1:1), covered with a glass watch glass. After dissolution, the solution was cooled and transferred to volumetric flask with a capacity of 1 DM, made up to the mark with water and mix. 50 cmof the solution transferred to a volumetric flask with a capacity of 500 cmadd 6 cmof a hydrochloric acid solution (1:1), made up to the mark with water and mix.

1 cmof the solution contains 0.0001 g of magnesium.

Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid 2-water (Trilon B) according to GOST 10652, 0.01 M solution: 3,723 g Trilon B dissolved in water, the solution transferred to a volumetric flask with a capacity of 1 DM, dilute to the mark with water and mix.

To establish the mass concentration of the solution Trilon B 25 cmstandard solution of magnesium was placed in a conical flask with a capacity of 500 cm. Add approximately 110 cmwater, 10 cmof ammonium chloride solution and set pH 8−9 by adding ammonia. The solution is heated to a temperature of 40−60 °C, add 10 cmof buffer solution and 0.2−0.3 g of indicator mixture. The solution was then titrated with a solution of Trilon B till the transition of the red color in blue.

Mass concentration (g/l) of Trilon B solution, expressed in grams of magnesium, 1 cm, calculated by the formula

, (4)

where is the mass of magnesium in the titrated standard solution, g;

 — volume of solution Trilon B, spent on titration, sm.

6.3. Analysis

A portion of the alloy with a mass of 2 g is dissolved in 50 cmof sulfuric acid solution (1:9), filtered the undissolved copper and washed it on the filter 3 times with hot water. To the cold filtrate was poured 1 cmof the ferric chloride solution and with constant stirring gradually introduce 60 cmsolution (300 g/DM) of sodium hydroxide.

After 10 minutes separate the mixture of hydroxides of iron and magnesium by filtration through a leaky filter that is placed in a small amount of paper pulp made from ash-free filter. The flask and the filter cake washed 2 times with cold saline (20 g/DM) of sodium hydroxide. The filter with the precipitate is transferred to a flask in which to carry out the deposition, and dissolve the pellet in 20−25 cmof hot hydrochloric acid (1:4), breaking the filter with a glass rod. Then add ammonia until complete deposition of iron, is heated to the discharge of sediment and filtered through a medium density filter, the precipitate washed 5 times with water containing a small amount of ammonia. The filtrate was set to pH 4, add 25 cmof a solution of sodium diethyldithiocarbamate, and the mixture was left for 10−15 min to coagulate, then filtered off the precipitate through a double filter with a small amount filtrowanie mass. Precipitate was washed 4 times with water, collecting the filtrate and washings in a conical flask with a capacity of 500 cm, add 100 cmof water, 20 cmbuffer solution, 10 cmof ammonia, 0.05−0.1 g of indicator mixture and titrate with a solution of Trilon B to a transition of a purple color in the blue. Conduct the titration immediately after adding the indicator to avoid partial decomposition. At the same time spend analysis solution on the control

trying.

6.4 Processing of results

6.4.1 Mass fraction of magnesium in % is calculated by the formula

, (5)

where is the mass concentration of Trilon B, expressed in grams of magnesium per 1 cmof the solution in g/cm;

 — volume of solution Trilon B, used for titration of the sample solution, cm;

 — volume of solution Trilon B, used for titration of the solution in the reference experiment, cm;

 — the weight of the portion of the sample,

G.

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.