GOST 851.7-93

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  ГОСТ 851.7-93

GOST 851.7−93 Magnesium primary. Method of determination of chlorine

GOST 851.7−93

Group B59

INTERSTATE STANDARD

MAGNESIUM PRIMARY

Method of determination of chlorine

Primary magnesium.
Method for determination of chlorine

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 78 inter-state standard GOST 851.7−93 introduced directly as state standard of the Russian Federation from January 1, 1997

4 REPLACE GOST 851.7−87

5 REISSUE

INFORMATION DATA

REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard specifies the turbidimetric method for the determination of chlorine (if chlorine mass fraction from 0.002% to 0,010%) in primary magnesium.

The method is based on formation of fine-dispersed Sol of silver chloride and subsequent measurement of optical density of the solution.

1 General requirements

1.1 General requirements to the method of analysis according to GOST 25086.

1.2 Mass fraction of chlorine is determined from two parallel batches.

2 Equipment, reagents and solutions

The photoelectric colorimeter.

Sulphuric acid — according to GOST 4204, diluted 1:3.

Nitric acid — according to GOST 4461, diluted 1:3.

Sodium chloride is particularly clean — according to GOST 4233.

Silver nitrate — GOST 1277, a solution with a mass concentration of 2 g/DM; store in a container made of dark glass.

Ammonia water according to GOST 3760, a solution with a mass concentration of 100 g/DM.

The standard solutions of chlorine:

Solution a: 1,650 g of sodium chloride, dried at a temperature 378−388 K, dissolved in water, transferred 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.

1 cmof the solution contains 1 mg of chlorine.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix; prepare before use.

1 cmof the solution contains 0.02 mg of chlorine.

3 analysis

3.1 Sample weighing 1.0 g was placed in a beaker with a capacity of 200 cm, moistened with water and poured in small portions of 20 cmof sulfuric acid solution (or 35 cmof nitric acid). After complete dissolution of the sample solution was cooled to room temperature, transferred to a volumetric flask with a capacity of 50 cm, add 5 cmof nitric acid (if the dissolution was carried out with a sulfuric acid solution), 5 cmof a solution of silver nitrate and left in dark place for 15 min. the solution was Then topped to the mark with water, mix and measure the optical density at a wavelength of 400 nm. Solution comparison is the solution of the reference experiment.

3.2 To prepare the solution in the reference experiment in a volumetric flask with a capacity of 50 cmis placed 5 cmof nitric acid, add 40 cmof water 5 cmof a solution of silver nitrate and then do as described in 3.1.

3.3 Construction of calibration curve

To build a calibration curve in seven of the eight volumetric flasks with a capacity of 50 cmplaced 1,0; 1,5; 2,0; 2,5; 3,0; 4,0; 5,0 cmstandard solution B, which corresponds to 0,02; 0,03; 0,04; 0,05; 0,06; 0,10 mg of chlorine. The eighth solution of the flask is a solution of the reference experiment.

All flasks are poured 5 cmof a solution of nitric acid, water to a volume of 40 cm, 5 cmsolution of silver nitrate and then do as described in 3.1.

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

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

After analyzing the volumetric flask is boiled in ammonia solution for removal of the walls of the remnants of chloride of silver.

4 processing of the results

4.1 Mass fraction of chlorine (the) percentage is calculated by the formula

, (1)

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

 — the weight of the portion,

4.2 Standards of accuracy of analysis results

The values of the characteristics of error definitions: permissible divergence of the results of the parallel definition (a measure 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

4.3 Control of accuracy of analysis results

Control the accuracy of the results of the analysis carried out by the method of additives in accordance with GOST 25086.

Additives is a standard solution B.

4.4 When placing the results of the analysis make reference to this standard and report the results of accuracy control.