GOST 25278.14-87

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  ГОСТ 25278.14-87

GOST 25278.14−87 Alloys and alloys of rare metals. Method for the determination of tantalum

GOST 25278.14−87

Group B59

STATE STANDARD OF THE USSR

ALLOYS AND ALLOYS OF RARE METALS

Method for the determination of tantalum

Alloys and foundry alloys of rare metals. Method for determination of tantalum

AXTU 1709

Valid from 01.07.88
to 01.07.93*
________________________________
* Expiration removed
according to the Protocol of the Intergovernmental Council
for standardization, Metrology and certification
(IUS N 2, 1993). — Note the manufacturer’s database.

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of nonferrous metallurgy of the USSR

PERFORMERS

E. S. Danilin, T. M. Malyutina

2. APPROVED AND promulgated by the Decree of the State Committee USSR on standards on 29 October 1987 N 4091

3. The period of examination — 1993

The frequency of inspection is 5 years.

4. INTRODUCED FOR THE FIRST TIME

5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard specifies the extraction-photometric method for the determination of tantalum (from 4 to 35%) in the alloys based on niobium and hafnium.

The method is based on extraction of tantalum from tartrate-sulfate medium by a mixture of toluene and acetone (9:1) in the form of fortuntate brilliant green and fotomaterialy coloring extract.

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis and security requirements — according to GOST 26473.0−85.

2. APPARATUS, REAGENTS AND SOLUTIONS

Photoelectrocolorimeter FEK-56 or similar device.

Tile electric.

Muffle furnace with thermostat providing temperatures up to 1000 °C.

Analytical scale.

Libra technical.

Volumetric flasks with a capacity of 100, 250 and 500 cm.

Pipettes with volume capacity of 1, 2, 5 and 10 cm.

Pipettes with piston with graduations up to 10 cm.

Glass vials with a capacity of 20 cm.

Tube racks, covered with black paper.

The quartz cylinders with ground stoppers with a capacity of 50 cm.

Stopwatch or hourglass for 1 and 3 min.

The quartz crucibles high capacity of 40 cm.

Sulfuric acid GOST 4204−77 and a solution of 9 mol/DM.

Hydrofluoric acid according to GOST 10484−78 and a solution of 2 mol/DM.

The sodium sulfate Piro GOST 18344−78, preheated at 200−250 °C for 5−10 min, the Melt is cooled, break into pieces, put them in a jar with a glass stopper.

Ammonium vinocity according to GOST 4951−79, a solution of 50 g/DM(filtered through the filter medium density, «the white ribbon»); prepared on the day of use.

Solution for dilution, is prepared as follows: into a measuring flask with a capacity of 250 cm200 cm pour thesolution Vinokurova ammonium 50 g/DM, add 20 cmof a solution of sulfuric acid 9 mol/DMand bring to mark with water. The solution is prepared the day of use.

Ammonium oxalate according to GOST 5712−78, a solution of 50 g/DM.

Acetone according to GOST 2603−79.

Toluene according to GOST 5789−78.

A mixture of toluene with acetone with the volume ratio 9:1, prepared on the day of use.

Diamond green, a solution of 15 g/DM, is prepared as follows: 7.5 g dye are dissolved in 500 cmof water when heated above 60 °C, allowed to stand in a dark place for 2−3 days, then filtered through a dense filter 2 («blue ribbon»), and the solution is stored in dark bottles.

Tantalum (V) oxide containing at least 99.9% of the main substance.

Tantalum metal containing at least 99.9% of tantalum, in the form of small chips.

Standard solution tantalum (spare) containing 0.5 mg/cmof tantalum: 0.1 g of tantalum metal or 0,1221 g of an oxide of tantalum was placed in a quartz crucible, add 3−4 g of picosulfate sodium, and fused in a muffle at 800−900 °C to produce a clear float. If fusion takes place incompletely, the melt is cooled, add 3−5 drops of concentrated sulfuric acid and re-fused to obtain a liquid transparent water. If necessary, the procedure of zaplavlenie repeated 2−3 times with the addition of concentrated sulfuric acid. The fusion is dissolved by boiling in 50 cmhot solution of ammonium oxalate, the solution was transferred into a measuring flask with a capacity of 200 cm, cooled, adjusted to the mark with a solution of ammonium oxalate and stirred.

A solution of tantalum (work) containing 10 µg/cmof tantalum, is prepared on the day of use as follows: in a volumetric flask with a capacity of 50 cmtransfer pipette 1 cmstandard backup solution tantalum, up to 4 cmof sulfuric acid solution with concentration 9 mol/DMand bring to mark with a solution of ammonium Vinokurova.

3. ANALYSIS

3.1. A portion of the sample with a mass of 0.1 t was placed in a quartz crucible, add 3−4 g of picosulfate sodium, a few drops of concentrated sulphuric acid and fused in a muffle at a temperature of 700−800 °C to produce a clear float. If fusion takes place incompletely, the melt is cooled, add 3−5 drops of concentrated sulfuric acid and re-fused to obtain a liquid transparent water. If necessary, the procedure of zaplavlenie repeated 2−3 times with the addition of concentrated sulfuric acid; then sulfuric acid is completely removed by heating before the termination of allocation of steams of sulfuric acid.

The fusion is dissolved by boiling in 30 cmof a solution of ammonium Vinokurova, transferred to a volumetric flask with a capacity of 50 cm, cooled, adjusted to the mark with a solution of ammonium Vinokurova, mix. Pipetted 1 cmof solution in a volumetric flask with a capacity of 25 cm, add 2 cmof a solution of sulfuric acid 9 mol/DM, adjusted to the mark with a solution of ammonium Vinokurova and stirred.

3.2. For the determination of tantalum in a quartz cylinder is taken 2 cmof the resulting solution, diluted to 10 cmwith a solution for dilution, add 10 cmof a mixture of toluene with acetone, 2 cmof a solution of hydrofluoric acid of 2 mol/DM, 1 cmof solution of brilliant green. Vigorously shake the cylinder for 1 min. after 3 min take with a dry pipette piston 7 cmof the extract, which is transferred to a tube containing 3 cmof acetone. Measure the optical density of the extract on photoelectrocolorimeter at 640 nm in a cuvette with the thickness of the light absorbing layer 10 mm relative to the

de.

3.3. A control experiment is conducted through all stages of the analysis along with an analysis of a series of samples. Optical density of the solution in the reference experiment compared to the water should not exceed 0.02 to 0.03, otherwise change the reagents.

A lot of tantalum find in the calibration schedule.

3.2. Construction of calibration curve

In quartz cylinders with ground stoppers pour 0,1; 0,2; 0,4; 0,8; 1,0; 1,5; 2,0; 2,5; 3,0; 3,5 and 4.0 cmworking solution of tantalum, which corresponds to 1, 2, 4, 8, 10, 15, 20, 25, 30, 35 and 40 µg of tantalum, diluted to 10 cmwith a solution for dilution, add 10 cmof a mixture of toluene with acetone, 2 cmof a solution of hydrofluoric acid of 2 mol/DM; 1 cmof solution of brilliant green. Vigorously shake the cylinder for 1 min. after 3 min take with a dry pipette piston 7 cmof the extract, which is transferred to a tube containing 3 cmof acetone. Measure the optical density of the extracts on the photoelectrocolorimeter FEK-56 at 640 nm in a cuvette with the thickness of the light absorbing layer 10 mm relative to the water.

According to the obtained results build a calibration curve in the coordinates of the optical density — the mass of tantalum. Separate test points of the graph along with the analysis of samples.

4. PROCESSING OF THE RESULTS

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

,

where  — weight of tantalum was found in the calibration schedule, mcg;

the capacity of volumetric flasks at the first dilution, cm;

the capacity of the volumetric flask for the second dilution, cm;

 — aliquotes volume of the solution taken for dilution, cm;

 — aliquotes volume of the solution taken for the determining, cm;

 — the weight of the portion of the sample,

G.

4.2. Discrepancies between the results of two parallel determinations and the results of the two tests should not exceed the values of permissible differences given in the table.