GOST 13637.6-93

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  ГОСТ 13637.6-93

GOST 13637.6−93 Gallium. Method for the determination of selenium

GOST 13637.6−93

Group B59

INTERSTATE STANDARD

GALLIUM

Method for the determination of selenium

Gallium.
Method for the determination of selenium

AXTU 1709

Date of introduction 1995−01−01

Preface

1. DEVELOPED by the Interstate technical Committee 104 «of the Semiconductor and rare metals products. Especially pure metals», State Institute of rare metals (Giredmet)

INTRODUCED by Gosstandart of Russia

2. ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 4−93 of 19 October 1993)

The adoption voted:

3. Resolution of the Committee of the Russian Federation for standardization, Metrology and certification from 02.06.94 N 160 inter-state standard GOST 13637.6−93 introduced directly as state standard of the Russian Federation from 01.01.95

4. REPLACE GOST 13637.6−77

INFORMATION DATA

REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard specifies a method for Stripping alternating-current voltammetry for the determination of selenium in Gaul (at the mass fraction of selenium from 5·10to 1·10%).

The method is based on the allocation of selenium in elemental form on the collector — sulfur determination by the method of inversion, alternating-current voltammetry with accumulation in the solution of sulfuric acid in the presence of ions of dichromate and copper (II).

1. GENERAL REQUIREMENTS

General requirements for methods of analysis and security requirements — according to GOST 13637.0−93.

2. APPARATUS, REAGENTS AND SOLUTIONS

Electronic laboratory 1 class according to GOST 24104*.
_______________
* On the territory of the Russian Federation GOST 24104−2001. — Note the manufacturer’s database.

Polarograph PPT-1 or PU-1 with the stationary mercury electrode and electrolytic cell polarograph with a remote anode compartment. The anode compartment is filled with a mixture of sulfuric acid, phosphoric acid and distilled water in volume ratio 1:1:2 (mercuriality the reference electrode).

Tile electric power of 400 watts.

Water bath.

The roughing pump brand VM-461М or similar.

Glass vials with a capacity of 50 cm.

Sticks to glass.

Conical flasks with a capacity of 250 cm.

Funnels, glass, with a diameter of 75 mm.

Volumetric flasks with a capacity of 25; 50; 100; 1000 cm.

Beakers with a capacity of 100; 500; 1000 cm.

Measuring cylinders with a capacity of 5 and 10 cm.

Pipette with divisions of 0,1; 0,2; 1; 2 cm.

The quartz crucibles with a capacity of 50 cm.

The chemical glasses with a capacity of 25; 100; 200; 1000 cm.

Watch-glasses with a diameter of 70 mm.

Filters «white ribbon».

Filter paper.

Ethyl alcohol according to GOST 18300.

Barium chloride, OS.h. according to GOST 4108.

Sodium carnavalito acid (sodium thiosulfate) 5-water according to GOST 27068 — recrystallized, aqueous solution concentration of 300 g/DM.

Sulfuric acid of high purity according to GOST 14262 — purified, and concentrated solutions concentration 9; 0,9 and 0,3 mol/DM.

The purified sulfuric acid in a beaker with a capacity of 1000 cm300 cm pouredwith bidistilled water and carefully poured, with stirring, 300 cmof concentrated sulfuric acid. The resulting solution is heated, pour the 10−15 cmof an aqueous solution of sodium chernovetskogo. The next day the solution was decanted and evaporated until the appearance of white fumes of sulfuric acid. The solution was added 50 mg of barium chloride. The mixture was heated until complete dissolution of barium sulfate, cooled, diluted with bidistilled water in a ratio of 1:1. The next day the solution was decanted and evaporated until the appearance of white fumes of sulfuric acid.

Potassium hydroxide according to GOST 24363.

Potassium permanganate according to GOST 20490.

Distilled water according to GOST 6709.

Bidistilled water: distilled water is poured into the flask of the distillation apparatus with a capacity of 2 DM. It is poured 1 g of potassium hydroxide and potassium permanganate to intense staining. The solution was heated. Collect the middle fraction of the distillate component of the taken volume of distilled water, the first and third fractions discarded.

Formic acid according to GOST 5848.

Nitric acid of high purity according to GOST 11125.

Hydrochloric acid of high purity according to GOST 14261 concentrated and distilled.

Aqua Regia a mixture of concentrated nitric and hydrochloric acids in a volume ratio of 1:3.

Reverse Aqua Regia — a mixture of concentrated nitric and hydrochloric acids in a volume ratio of 3:1.

Hydroxylamine hydrochloride according to GOST 5456, solution concentration 100 g/lsolution of hydrochloric acid concentration is 6 mol/DM.

The washing liquid: a solution of hydroxylamine hydrochloride was diluted with bidistilled water in a ratio of 1:5 by volume.

Bromine according to GOST 4109.

Potassium dichromate according to GOST 4220, an aqueous solution concentration of 50 g/lin sulfuric acid concentration of 0.9 mol/DM.

Copper (II) sulfate 5-water according to GOST 4165, an aqueous solution of a copper concentration of 500 g/cmin a solution of sulfuric acid concentration of 0.9 mol/DM.

Sulfur milk: to 10 cmsolution carnavalito acid sodium was added 4 cmof dilute sulfuric acid 1:1 immediately before use (1−2 min).

Mercury brands r0 according to GOST 4658.

Selenium of high purity.

The main selenium solution: 100 mg of selenium dissolved in reverse Aqua Regia; add 5 cmof concentrated sulfuric acid and the solution is evaporated prior to the allocation of sulphuric acid fumes. The resulting solution was transferred to volumetric flask with a capacity of 100 cmand adjusted to the mark with bidistilled water.

1 cmcore solution contains 1 mg selenium.

More diluted solutions were prepared by diluting stock solution of selenium in sulfuric acid solution with a concentration of 0.9 mol/DMon the day of use.

The technical rectified ethyl alcohol according to GOST 18300 is used when charging the electrodes in accordance with the instructions for polarography.

3. ANALYSIS

3.1. Dissolution samples

A portion of gallium content of 1 g dissolved in 10 cmreverse Aqua Regia into a crucible with a capacity of 50 cm. The solution is evaporated to dryness and carry out denitration residue of formic acid. For this, the cooled crucible is gently dropwise added 0.5−1 cmof formic acid and put in water bath. This operation is repeated until the complete termination of allocation of oxides of nitrogen. Then the residue is treated with distilled water and evaporated in a water bath. The excess formic acid is removed by evaporation of water. Traces of formic acid do not interfere with the further course of the analysis. Then the residue is dissolved in 20 cmof hydroxylamine hydrochloride. The solution was transferred to a test tube with a capacity of 50 cm. Tubes with a solution placed in a boiling bath. They add 0.5 cmof sulfur milk and incubated the solutions on water bath for 3 h. During this time, three times add 0.3 cmsulfur milk — after 30 min, 1 h and 3 h. the next day the separated precipitate of sulphur containing selenium, filtered through a filter with a white ribbon and washed first seven times of the rinsing liquid, and then five times with double-distilled water. The precipitate is washed with a jet of double-distilled water in a crucible with a capacity of 50 cm. Add 1 cmof concentrated nitric acid, 1 cmof sulfuric acid diluted 1:1 and 0.5 cmof bromine. The crucible is left under watch glass for 30 min. the solution was Then heated in a water bath until distillation of the excess bromine is evaporated and on the tile before the advent of the vapors of sulfuric KIS

lots.

3.2. Polarographically

To the contents of the cooled crucible, add 5 cmdouble-distilled water, 0.2 cmof a solution of potassium dichromate and 0.2 cmof a solution of copper sulphate. The contents of the crucible are slightly heated until complete dissolution of the precipitate, the solution was cooled and transferred to a measuring cylinder with a capacity of 50 cm, bring the solution volume up to 25 cmdouble-distilled water. Polarography of the analyzed solution are in cell polarography mercuriality with a remote reference electrode. The size of the stationary mercury drop must match 20 ticks of the clock indicator polarograph. The accumulation potential of minus 0.6 volts, the duration of accumulation with stirring for 1−3 min, settling time of 15 s. solution the cathodic Sweep, sweep rate 5 mV/s, amplitude 8 MB. The peak potential of about minus Selena of 1.05 V. the Voltammogram of each solution is removed three times.

3.3. Transcript of inversion voltammograms

The peak height is measured vertically, is drawn through the top of the peak to the intersection with a tangent connecting the bases of the branches peak. Each of the peak heights should not vary from the arithmetic average of the peak height by more than 0.2 . If the height of the first peak differs from the average by more than 0.2 , the height of the first peak is not considered.

Mass fraction of selenium in the sample is determined by method of additions. The addition of the diluted standard solution of selenium of not more than 0.3 cmis introduced into the entire volume polarographic solution.

The solution with the addition of polarographic the same way as the sample solution. Supplement should to increase the mass of selenium in polarographic solution and the peak height of 2−3 times, if the content of selenium in the sample , calculated according to claim 4.1, at least 5·10%.

If the mass fraction of selenium in the sample is less than 5·10%, the additive should be 0.05 µg.

With each series of samples is carried out two test experience.

4. PROCESSING OF THE RESULTS

4.1. Mass fraction of selenium () in percent is calculated by the formula

,

where is the mass of selenium in Supplement mcg

 — arithmetic average peak height polarographic solution sample sample minus the arithmetic mean values of the peak height of selenium in a control experiment, mm

the weight of gallium in the solution polarographically, g,

 — arithmetic average peak height of the sample solution of the sample with the additive minus the arithmetic mean values of the peak height of selenium in a control experiment, mm

 — polarographically the volume of sample solution, cm,

 — volume Supplement, see

.

4.2. The result of the analysis taking the arithmetic average of the two results of parallel measurements carried out from separate batches.

The allowable discrepancy of the two results of parallel measurements and the two results of the analysis (the difference between larger and smaller) with confidence probability of 0.95 is given in the table.

Permitted discrepancies for the intermediate mass fraction of selenium calculated using linear interpolation.

4.3. Control of the correctness analysis is carried out by additives according to GOST 25086.