GOST 20996.7-2014

• gost-209967-2014.pdf (426.34 KiB)
  ГОСТ 20996.7-2014

GOST 20996.7−2014 Selenium technical. Methods for determination of aluminium

GOST 20996.7−2014

INTERSTATE STANDARD

SELENIUM TECHNICAL

Methods for determination of aluminium

Selenium technical. Methods of aluminum determination

OKS 77.120.99

Date of introduction 2016−01−01

Preface

Goals, basic principles and main procedure of works on interstate standardization established in GOST 1.0−92 «interstate standardization system. Basic provisions» and GOST 1.2−2009 «interstate standardization system. Interstate standards, rules and recommendations on interstate standardization. Rules of development, adoption, renewal and cancellation"

Data on standard

1 DEVELOPED by the Open joint-stock company «Scientific-research and design Institute of enrichment and mechanical processing of minerals «URALMEKHANOBR» (JSC «uralmekhanobr»), Technical Committee for standardization TC 368 «Copper"

2 as AMENDED by the Federal Agency for technical regulation and Metrology

3 ACCEPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 72-P of 14 November 2014)

The standard was accepted by voting:

4 by Order of the Federal Agency for technical regulation and Metrology from 02 APR 2015 N 210th St interstate standard GOST 20996.7−2014 introduced as the national standard of the Russian Federation from January 01, 2016

5 REPLACE GOST 20996.7−82


Information about the changes to this standard is published in the annual reference index «National standards», and the text changes and amendments — in monthly information index «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in the monthly information index «National standards». Relevant information, notification and lyrics are also posted in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet

1 Scope

This standard establishes photometric methods of measurements of mass fraction of aluminium (in the range from 0.002% to 0,060%).

2 Normative references

The present standard features references to the following international standards:

GOST 61−75 Reagents. The acetic acid. Specifications

GOST 199−78 Reagents. Sodium acetate 3-water. Specifications

GOST 1770−74 (1042−83 ISO, ISO 4788−80) Glassware volumetric laboratory glass. Cylinders, beakers, flasks, test tubes. General specifications

GOST 2062−77 Reagents. Acid bromatologica. Specifications

GOST 3117−78 Reagents. Ammonium acetate. Specifications

GOST 3118−77 Reagents. Hydrochloric acid. Specifications

GOST 3760−79 Reagents. The aqueous ammonia. Specifications

GOST 4461−77 Reagents. Nitric acid. Specifications

GOST 6413−77 benzoic Acid technical. Specifications

GOST 6709−72 distilled Water. Specifications

GOST 11069−2001 primary Aluminium. Brand

GOST 11293−89 Gelatin. Specifications

GOST 18300−87ethyl rectified technical. Specifications
________________
On the territory of the Russian Federation GOST R 55878−2013 «ethanol technical rectified hydrolysis. Technical conditions».


GOST 20996.0−2014 Selenium technical. General requirements for methods of analysis

GOST 24104−2001laboratory Scales. General technical requirements
________________
On the territory of the Russian Federation GOST R 53228−2008 «Scales non-automatic actions. Part 1. Metrological and technical requirements. Test».


GOST 24363−80 Reagents. Potassium hydroxide. Specifications

GOST 25336−82 Glassware and equipment laboratory glass. The types, basic parameters and dimensions

GOST 29169−91 (ISO 648−77) oils. Pipette with one mark

GOST 29227−91 (ISO 835−1-81) oils. Pipettes are graduated. Part 1. General requirements

GOST ISO 5725−6-2003Accuracy (trueness and precision) of methods and measurement results. Part 6. The use of precision values in practice
________________
On the territory of the Russian Federation GOST R ISO 5725−6-2002 «Accuracy (trueness and precision) of methods and measurement results. Part 6. The use of precision values in practice».


Note — When using this standard appropriate to test the effect of reference standards in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet or in the annual information index «National standards» published as on January 1 of the current year, and the editions of the monthly information index «National standards» for the current year. If the reference standard is replaced (changed), when using this standard should be guided by replacing (amended) standard. If the reference standard is cancelled without replacement, then the situation in which the given link applies to the extent that does not affect this link.

3 General provisions

3.1 General requirements for methods of measurements GOST 20996.0.

4 Characteristics of indicators of measurement accuracy

Indicators of accuracy of measurements of mass fraction of aluminium correspond to the characteristics given in table 1 (with R=0,95).

Limit values of repeatability and reproducibility of the measurement at a confidence probability P=0.95 is given in table 1.


Table 1 — Values of the measure of the accuracy, limits of repeatability and reproducibility of measurements of mass fraction of aluminium

Percentage

5 Photometric method of measuring the mass fraction of aluminium with the use of aluminon

5.1 measurement Means, auxiliary devices, materials, solutions

When performing measurements using the following measuring instruments and auxiliary devices:

— spectrophotometer or photocolorimeter with all accessories necessary for measurements at a wavelength of 530 to 535 nm;

— heating glass-ceramic plate according to [1]* or similar, ensuring the heating temperature up to 400 °C;
________________
* POS. [1], [2], [4]-[8] see Bibliography. — Note the manufacturer’s database.


— pH meter;

glass hour;

— special laboratory scales of accuracy class according to GOST 24104;

— volumetric flasks 2−50−2, 2−100−2, 2−500−2, 2−1000−2 according GOST 1770;

— glasses N-2-TXC 100, H-2-TXC 250, N-2-TXC 1000 according to GOST 25336;

— flask with a glass stopper;

— funnel In-36−80 TC GOST 25336;

pipettes not lower than 2nd accuracy class according to GOST and GOST 29169 29227.

When taking measurements, use the following products and solutions:

— distilled water according to GOST 6709;

— nitric acid according to GOST 4461;

— hydrochloric acid according to GOST 3118, diluted 1:1;

— acetic acid according to GOST 61, a solution of a molar concentration of 0.2 mol/DM;

— ascorbic acid by [2], a freshly prepared solution of the mass concentration of 20 g/DM;

— benzoic acid technical GOST 6413;

— ammonium acetate according to GOST 3117;

— ethyl alcohol according to GOST 18300;

— aluminon [3];

— ammonia water according to GOST 3760, diluted 1:1;

— gelatin according to GOST 11293;

— aluminium GOST 11069;

acid bromatological according to GOST 2062;

— thioglycolic acid by [4], diluted 1:10;

filters obestochennye in [5], or equivalent;

paper universal indicator [6].

5.2 the essence of the method

The method is based on the reaction of formation of colored compounds of aluminum ions with alumininum at a pH of from 4.5 to 4.8 after prior separation of selenium by evaporation with bromatological acid and subsequent measurement of optical density at a wavelength of 530 nm.

5.3 Preparation for measurements

5.3.1 Preparation of solutions for constructing the calibration curve

In preparing the solution And the mass concentration of aluminium of 0.1 mg/cmweighed aluminum weighing 0.1 g were placed in a glass with a capacity of 100 cm, flow 10 to 15 cmof hydrochloric acid diluted 1:1, transfer the solution into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

In the preparation of a solution with a mass concentration of aluminum of 0.01 mg/cma 10 cm aliquotof solution A is placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

5.3.2 Preparation aluminievaya buffer solution

A suspension of ammonium acetate with a mass of 125 g is placed in a volumetric flask with a capacity of 500 cm, a flow of 200 to 250 cmof water and 15 to 20 cmof acetic acid, stirred and measured pH. In a glass with a capacity of 100 cmis placed a portion of aluminon a mass of 0.25 g, flow 15 cmof water. The solution was transferred to a volumetric flask, which was prepared acetic acid solution. In a glass with a capacity of 100 cmis placed 5 g of benzoic acid, poured in 25 cmof ethanol, transferred to the same volumetric flask and mix. The mixture is topped up to the mark with water and mix.

In a glass with a capacity of 100 cmis placed 2.5 g of gelatin pour 70 to 80 cmof water and after an hour is heated to dissolve the gelatin. The hot solution is poured into a glass with a capacity of 250 cm, which is pre-placed 150 cmof water and stirred. After cooling, the solution is mixed with acetic acid solution in a beaker with a capacity of 1000 cm.

Pour water to a volume of 950 cmand set the pH of the solution with ammonia diluted 1:1 in the range from 4.5 to 4.8 (on the indicator paper or pH-meter). The solution was stirred and transferred into a measuring flask with volume capacity of 1000 cm, cooled, made up to the mark with water and mix. The resulting solution was filtered through a double thick filter, collecting the filtrate in a flask made of dark glass with a glass stopper. A clear solution stored in a dark place.

5.3.3 Construction of calibration curve

Eight volumetric flasks with a capacity of 100 cmplaced 0; 0,5; 1,0; 2,0; 3,0; 4,0; 5,0 and 7.0 cmof solution B, which corresponds to 0; 0,005; 0,01; 0,02; 0,03; 0,04; 0,05 and 0.07 mg of aluminum poured water up to 10 cm, add 1−2 drops of ascorbic acid mass concentration of 20 g/DMor thioglycolic acid, diluted 1:10. Poured from 15 to 17 cmaluminievaya buffer solution, heated in water bath for no more than 5 min before the formation of «aluminum Polish». The solution was cooled, made up to the mark with water and mix. After 15 min measure the optical density of the solution on photocolorimetry (spectrophotometer), using a filter with maximum transmittance at a wavelength of 530 to 535 nm and cuvette thickness of the absorbing layer is from 20 to 30 mm.

On the found values of optical densities of solutions and their corresponding grades of aluminium to build the calibration graph.

5.4 performance measurement

A portion of the selenium mass in accordance with table 2 depending on the mass fraction of aluminium is placed in a beaker with a capacity of 250 cm, flow 15 to 30 cmof nitric acid, cover with watch glass and allowed to stand without heating until the cessation of the violent reaction of the allocation of nitrogen oxides.


Table 2

Remove the glass, wash water over the glass and heat the solution to dissolve the sample and evaporated to dryness. Pour 8 to 10 cmof nitric acid and again evaporated to dryness. Poured from 5 to 7 cmof nitric acid, evaporated to dryness, the evaporation repeated two times.

To the dry residue poured 2 to 3 cmof hydrochloric acid, evaporated to dryness, poured 2 to 3 cmbromatological acid and again evaporated to dryness. Evaporation from bromatological acid repeat. Then to the dry residue poured 2 to 3 cmof hydrochloric acid, evaporated to dryness. Evaporation with hydrochloric acid is repeated twice. Removal of selenium dioxide may be carried out by heating on the stove at a temperature of from 280 °C to 290 °C.

Then pour 2 to 3 cmof hydrochloric acid of 25 to 30 cmof water and heated to dissolve the salts. After cooling, transfer the solution into a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

From the volumetric flask an aliquot taken of the solution in accordance with table 2 and transfer it into a measuring flask with a capacity of 100 cm. To the solution was added drop by drop ascorbic acid, the mass concentration of 20 g/DMor 1−2 drops of a solution of thioglycolic acid, diluted 1:10 for recovery of the iron binding in colorless complex, with a large excess of acid unwanted. If the solution is colorless, then add 1 drop of acid.

To the solution in a volumetric flask poured from 15 to 17 cmaluminievaya buffer solution, heated in water bath for no more than 5 min before the formation of «aluminum Polish». The solution was cooled, made up to the mark with water and mix. After 15 min measure the optical density of the solution on photocolorimetry (spectrophotometer), using a filter with maximum transmittance at a wavelength of 530 to 535 nm and cuvette thickness of the absorbing layer is from 20 to 30 mm.

As a solution comparison, using a solution of «blank» experience.

A lot of aluminum in milligrams set by the calibration schedule.

6 Photometric method of measuring the mass fraction of aluminium with the use of chromazurol

6.1 measurement Means, auxiliary devices, materials, solutions

When performing measurements using the following measuring instruments and auxiliary devices:

— spectrophotometer or photocolorimeter with all accessories necessary for measurements at a wavelength of 545 nm;

— heating glass-ceramic plate according to [1] or similar, ensuring the heating temperature up to 400 °C;

— bath water;

— pH meter;

glass hour;

— special laboratory scales of accuracy class according to GOST 24104;

— volumetric flasks 2−100−2, 2−250−2 according GOST 1770;

— glasses-1−250 TCS according to GOST 25336;

— flasks KN-2−250−19/26 according to GOST 25336.

When taking measurements, use the following products and solutions:

— distilled water according to GOST 6709;

— nitric acid according to GOST 4461;

— hydrochloric acid according to GOST 3118, diluted 1:1 solution of molar concentration 0.1 mol/DMprepared with a standard caption;

— acetic acid according to GOST 61;

— sodium acetate according to GOST 199;

— ethyl alcohol according to GOST 18300;

— aluminium GOST 11069;

acid bromatological according to GOST 2062;

— thioglycolic acid by [4], diluted 4:100;

— potassium hydroxide (hydroxide) according to GOST 24363, solution mass concentration of 0.01 g/DM;

— phenolphthalein indicator [7], an alcoholic solution of the mass concentration of 0.01 g/DM;
— chromazurol S indicator [8], water-alcohol solution of the mass concentration of 0.02 g/DM.

6.2 Method of measurement

The method is based on the reaction of formation of colored compounds of aluminum ions with chromazurol at a pH of from 5.7 to 5.8 in the presence of thioglycolic acid to mask the ions of iron and copper, and subsequent measurement of optical density at a wavelength of 545 nm.

6.3 preparing the measurements

6.3.1 Preparation of solutions for constructing the calibration curve

To construct the calibration curve, prepare solutions of known concentration of aluminium in 5.3.1.

6.3.2 Construction of calibration graphs

In seven volumetric flasks with a capacity of 100 cmplaced 0; 0,5; 1,0; 1,5; 2,0; 2,5; 3,0 cmof solution B, which corresponds to 0; 0,005; 0,010; 0,015; 0,020; 0,025; 0,030 mg of aluminium. Diluted with water to a volume of 15 cm, add 1 to 2 drops of phenolphthalein and then do as specified in 5.5.3

On the found values of optical densities of solutions and their corresponding grades of aluminium to build the calibration graph.

6.3.3 Preparation of acetate buffer solution with a pH of 5,8−6,0

A suspension of sodium acetate mass of 75 g is placed in a beaker with a capacity of 250 cm, is dissolved in 150 cmof water, poured 1.5 cmof acetic acid (density of 1.07) and top up with water to a volume of 250 cm. Control of the pH value on the pH meter.

6.3.4 preparation of a water-alcohol solution of chromazurol S

For the preparation of an aqueous-alcoholic solution of chromazurol S mass concentration of 0.02 g/DMa portion of chromazurol S with a mass of 0.2 g is placed in a flask with a capacity of 250 cm, pour the 30 cmwater and 25 cmof ethyl alcohol and add water to volume of 100 cm. If the solution is turbid, it is filtered.

6.4 performance measurement

A portion of the selenium mass depending on the mass fraction of aluminum in accordance with table 3 was placed in a beaker with a capacity of 250 cm, flow 15 to 20 cmof nitric acid, cover with watch glass and allowed to stand without heating until the cessation of the violent reaction of the allocation of nitrogen oxides. Remove the glass, wash it with water over the beaker and the solution was evaporated by heating to dryness.


Table 3

Poured from 7 to 10 cmof nitric acid and again evaporated to dryness.

To the dry residue pour from 3 to 5 cmbromatological acid and evaporated to dryness. Again pour from 3 to 5 cmand bromatological hydrochloric acid and evaporation to dryness is repeated. Then pour 5 cmof hydrochloric acid of 25 to 30 cmof water and heat the solution to dissolve the salts. After cooling, placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Take an aliquot of the solution according to table 3 and placing it in a volumetric flask with a capacity of 100 cm, is diluted with water to a volume of 25 cm. To the solution add 1−2 drops of phenolphthalein and neutralized with potassium hydroxide solution until the appearance of violet colouration of the solution, then add dropwise a solution of hydrochloric acid molar concentration of 0.1 mol/DMto discoloration and 5 cm. Go 0.3 cmof a solution of thioglycolic acid, diluted 4:100 and mix.

After 5 min, dilute with water to volume of 50 cm, pour 1 cmof a solution of chromazurol S, 10 cmof ethanol, 5 cmacetate buffer solution, made up to the mark with water and mix.

After 15 min measure the optical density of the solution on the spectrophotometer or photocolorimeter at a wavelength of 545 nm in a cuvette with a layer thickness of 10 mm. as a solution comparison, using the solution of «idle» experience, carried out through all stages of measurement and containing 1 cmof chromazurol.

A lot of aluminum in milligrams set by the calibration schedule.

7 Processing measurement results

7.1 Mass fraction of aluminum X, %, is calculated by the formula

, (1)

where mis the mass of aluminum was found in the calibration graphics mg;

V — volume of solution in a volumetric flask, cm;

m — mass of sample selenium, g;

V — volume of the aliquot solution, cm;

1000 — transferable multiplier milligrams to grams.

7.2 measurement results take the arithmetic mean of two parallel definitions, provided that the absolute difference between them in terms of repeatability does not exceed the value (at confidence probability P=0,95) repeatability limit rgiven in table 1.

If the difference between the highest and lowest results of parallel measurements exceeds the limit value of the frequency of occurrence, perform the procedure described in GOST ISO 5725−6 (paragraph 5.2.2.1).

7.3 Discrepancies between measurements obtained in two laboratories, should not exceed the limit values for the reproducibility given in table 1. In this case, the final result can be accepted their mean value. At default of this condition can be used the procedure set out in GOST ISO 5725−6.

7.4 When differences in the assessment of mass fraction of aluminium used method of measuring alumininum.

Bibliography

________________
* The one referred to here and hereinafter, not shown. For additional information, please refer to the link. — Note the manufacturer’s database.