GOST 851.2-93

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  ГОСТ 851.2-93

GOST 851.2−93 Magnesium primary. Methods for determination of silicon

GOST 851.2−93

Group B59

INTERSTATE STANDARD

MAGNESIUM PRIMARY

Methods for determination of silicon

Primary magnesium.
Methods for determination of silicon

ISS 77.120.20
AXTU 1709

Date of introduction 1997−01−01

Preface

1 DEVELOPED by the Ukrainian scientific-research and design Institute of titanium

INTRODUCED by Gosstandart of Ukraine

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 3 dated February 17, 1993)

The adoption voted:

3 Decree of the Russian Federation Committee on standardization, Metrology and certification from February, 20th, 1996 N 73 inter-state standard GOST 851.2−93 introduced directly as state standard of the Russian Federation from January 1, 1997

4 REPLACE GOST 851.2−87

5 REISSUE

INFORMATION DATA

REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard establishes photometric methods for determination of silicon (with a mass fraction of silicon of from 0.002% to 0,060%) in primary magnesium.

1 General requirements

1.1 General requirements for methods of analysis GOST 25086.

1.2 Mass fraction of the silicon is determined from the two parallel batches.

1.3 When building a calibration curve each point build on the average result of the three definitions of optical density.

1.4 When placing the results of the analysis make reference to this standard, specify the method of determining, and method and results of control accuracy.

2 the Photometric method for the determination of silicon (with a mass fraction of silicon of from 0.002% to 0.020%)

2.1 the essence of the method

The method is based on formation of colored blue the recovered silicon-molybdenum complex compounds with subsequent measurement of optical density of the solution.

2.2 the Instrument, reagents and solutions

The spectrophotometer or photoelectric colorimeter.

Ionomer or pH meter.

Sulphuric acid — according to GOST 4204, diluted 1:1, 1:3, 1:240 and the solution with molar concentration of 1 mole/DM.

Ammonium molybdate — GOST 3765 recrystallized, solution with a mass concentration of 100 g/DM, stored in a plastic container.

Ammonium neccersarily — GOST 20478, a freshly prepared solution with a mass concentration of 50 g/DM.

Ascorbic acid according to the State Pharmacopoeia X, a freshly prepared solution with a mass concentration of 50 g/DM.

Sodium carbonate — GOST 83.

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

Magnesium sulfate 7-water according to GOST 4523, a solution with a mass concentration of 250 g/DM.

Silicon dioxide — according to GOST 9428, pre-calcined at a temperature of 1273 K.

State standard samples made in accordance with GOST 8.315.

Standard solutions of silicon:

Solution a: 0,214 g of silica fused in a platinum crucible with 5 g of sodium carbonate at a temperature of 1273 K for 30 min and the Melt is dissolved in water by heating in a platinum Cup. The solution was cooled to room temperature, filtered into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix; fit for use for 6 months.

The solution was stored in a plastic container with a tight-fitting plastic lid.

1 cmof solution A contains 0.1 mg of silicon.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix; prepare before use.

1 cmof a solution contains 0.01 mg of cream

niya.

2.3 analysis

2.3.1 Sample weight of 0.5 g was placed in a beaker with a capacity of 100 cm, cover with a watch glass, add 20 cmof a solution of ammonium naternicola. After 10 min of cessation of the violent reaction add 5 cmof sulfuric acid solution (1:3). Acid is poured slowly (with stirring) in small portions (0.5 cm).

After dissolution of the sample wall of the glass wash 5−10 cmof water and put in a boiling water bath for 30 min. the solution was Then cooled to room temperature, add water to volume of 50 cmand set the pH (1,4±0,1) using sulfuric acid solution with molar concentration of 1 mol/DMor ammonia solution (the pH of the solution is controlled by ionometer).

The solution was transferred to a volumetric flask with a capacity of 100 cm, the side of the Cup washed with 10 cmof water, adding 5 cmof ammonium molybdate solution and after 15 min — 10 cmof sulfuric acid solution (1:1). After 15 minutes add 5 cmof a solution of ascorbic acid and top up to the mark with water. After addition of each reagent the solution was stirred. After 20 minutes, measure the optical density of the solution at a wavelength of 810 nm on the spectrophotometer or from 630 nm to 750 nm on the photoelectric colorimeter. Solution comparison is the solution of the reference experiment.

The color of complex compounds resistant.

e 1 h

2.3.2 For preparation of solution control experience in a volumetric flask with a capacity of 100 cmare placed 50 cmof sulfuric acid solution (1:240), 5 cmof molybdenic acid ammonium solution and then do as described in 2.3.1.

2.3.3 Construction of calibration curve

To construct the calibration curve in two cups with a capacity of 100 cmplaced at 20 cmsolution of magnesium sulfate, in eight of them added 0,5; 1,0; 2,0; 3,0; 4,0; 6,0; 8,0; 10,0 cmstandard solution B, which corresponds to 0,005; 0,010; 0,020; 0,030; 0,040; 0,060; 0,080; 0,100 mg silicon. Solution the ninth glass is a solution in the reference experiment.

Add in all the cups 50 cmof sulfuric acid solution (1:240), set the pH (1,4±0,1) using sulfuric acid solution with molar concentration of 1 mol/DMor ammonia solution, the solutions are transferred to volumetric flasks with a capacity of 100 cm, washing the walls of the Cup 10 cmof water, add 5 cmof molybdenic acid ammonium solution and then do as described in 2.3.1.

Solution comparison is the solution of the reference experiment.

According to the obtained values of optical density calibration curve built in accordance with GOST 2508

6.

2.4 Processing of results of analysis

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

, (1)

where is the mass of silicon in the sample solution found by the calibration schedule g;

 — the weight of the portion,

2.4.2 Standards of accuracy of analysis results

The values of the characteristics of error definitions: permitted discrepancies in the results of parallel measurements (the rate of convergence) and the results of the analysis of the same samples obtained in two laboratories or in the same, but in different conditions (a measure of reproducibility), and the margins of error definitions ( — accuracy rate) at a confidence level =0.95 is shown in table 1.

Table 1

2.4.3 Control of accuracy of analysis results

Control of accuracy of analysis results is carried out according to state standard sample in accordance with GOST 25086.

It is allowed to conduct control of accuracy by the method of additives in accordance with GOST 25086. Additives is a standard solution B.

3 Photometric method for the determination of silicon (with a mass fraction of from 0.005% to 0,060%)

3.1 the essence of the method

The method is based on formation of yellow colored silicon-molybdenum complex compounds with subsequent measurement of optical density of the solution.

3.2 Equipment, reagents and solutions

The spectrophotometer or photoelectric colorimeter.

Sulphuric acid — according to GOST 4204, diluted 1:4.

Ammonium molybdate — GOST 3765, recrystallized, solution with a mass concentration of 100 g/DM, stored in a plastic container.

Ammonium neccersarily — GOST 20478.

Magnesium sulphate — 7-water — GOST 4523, a solution with a mass concentration of 250 g/DM.

State standard samples made in accordance with GOST 8.315.

Standard solutions of silicon:

Solution a: prepared according to 2.2.

Solution B: 50 cmsolution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix; prepare before use.

1 cmof the solution contains 0.05 mg of silicon.

3.3 analysis

3.3.1 Sample weighing 0.5 g were placed in a glass with a capacity of 200 cm, adding 25 cmof water, the beaker is placed in cold water and add small portions (0.5 cm) 7.5 cmof sulfuric acid solution (1:4). After complete dissolution of the sample add 1 cmof sulfuric acid solution (1:4) and 0.1 g of ammonium naternicola. After 10 minutes, the beaker content was transferred into a measuring flask with a capacity of 100 cm, add 5 cmof molybdate ammonium solution, made up to the mark with water and mix. After 15 min measure the optical density of the solution at a wavelength of 400 nm. Solution comparison is the solution of the reference experiment.

The color of complex compounds stable for 1 h

.

3.3.2 solution preparation control experience in a volumetric flask with a capacity of 100 cmpour 25 cmof water, add 1 cmof sulfuric acid solution (1:4), 0.1 g of ammonium naternicola and 10 min — 5 cmof a solution of molybdate of ammonium. Then do as specified in 3.3.1.

3.3.3 Construction of calibration curve

To build a calibration curve in seven of the eight volumetric flasks with a capacity of 100 cmplaced 0,5; 1,0; 2,0; 3,0; 4,0; 5,0; 6,0 cmstandard solution B, which corresponds to 0,025; 0,050; 0,100; 0,150; 0,200; 0,250; 0,300 mg silicon.

The eighth solution of the flask is a solution of the reference experiment.

To all flasks add 1 cmof sulfuric acid solution (1:4), 20 cmsolution of magnesium sulfate, 5 cmof molybdenic acid ammonium solution and then do as specified in 3.3.1.

According to the obtained values of optical density calibration curve built in accordance with GOST 25086.

3.4 Processing of analysis results

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

, (2)

where is the mass of silicon in the sample solution found by the calibration schedule g;

 — the weight of the portion,

3.4.2 Standards of accuracy of analysis results

The values of the characteristics of error definitions: permitted discrepancies in the results of parallel measurements (the rate of convergence) and the results of the analysis for the same samples, obtained in two laboratories or in the same, but in different conditions (a measure of reproducibility), and the margins of error definitions ( — accuracy rate) at a confidence level =0.95 is shown in table 2.

Table 2

3.4.3 Control of accuracy of analysis results

Control of accuracy of analysis results is carried out according to state standard sample in accordance with GOST 25086.

It is allowed to conduct control of accuracy by the method of additives in accordance with GOST 25086.

Additives is a standard solution B.