GOST 12697.12-77
GOST 12697.12−77 Aluminum. Methods for determination of arsenic (with Amendments No. 1, 2, 3, adjusted)
GOST 12697.12−77
Group B59
INTERSTATE STANDARD
ALUMINIUM
Methods for determination of arsenic
Aluminium. Methods for determination of arsenic
ISS 77.120.10
AXTU 1709
Date of introduction 1979−01−01
The decision of the State standards Committee of the Council of Ministers of the USSR from
Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 5−6-93)
EDITION with Amendments No. 1, 2, 3, approved in may 1983 to November 1985, may 1988 (IUS 9−83, 2−86, 8−88).
AMENDED, published in IMS No. 1, 2005
An amendment made by the manufacturer of the database
This standard specifies the photometric and polarographic methods for the determination of arsenic in aluminum.
(Changed edition, Rev. N 3).
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 12697.1−77 and GOST 25086−87.
(Changed edition, Rev. N 2, 3).
2. The PHOTOMETRIC METHOD for the DETERMINATION of ARSENIC (in mass fraction of arsenic from 0.0004 inch to 0.04%)
2.1. The essence of the method
The method is based on extraction of iodide of trivalent arsenic from hydrochloric acid solution with carbon tetrachloride and photocolorimetric determination in michalopolous blue.
2.2. Apparatus, reagents and solutions
Types photoelectrocolorimeter FEK-56M, PEC-60, KLF or the types of spectrophotometer SF-16, SF-26 or similar type.
Laboratory scales according to GOST 24104−88* 2nd accuracy class with the weighing error of 0.0002 g.
_________________
* From 1 July 2002 was put into effect GOST 24104−2001**.
** On the territory of the Russian Federation GOST R 53228−2008. — Note the manufacturer’s database.
Hydrochloric acid of high purity according to GOST 14261−77.
Nitric acid GOST 4461−77 diluted 1:1.
Sulfuric acid GOST 4204−77, diluted 1:1.
A mixture of acids: merge equal quantities of sulphuric acid, diluted with 1:1 hydrochloric acid, diluted 1:1 nitric acid, diluted 1:1.
Potassium iodide according to GOST 4232−74, a solution with a mass fraction of 0.1%.
Iodine GOST 4159−79, saturated solution; prepared as follows: 25 g of potassium iodide dissolved in 250 cmof water and add 20 g of crystalline iodine. The solution is kept over night. If all the iodine is dissolved, then add crystalline iodine to obtain a saturated solution.
Ascorbic acid, freshly prepared solution with a mass fraction of 0.4%.
Ammonium molybdate according to GOST 3765−78, a solution with a mass fraction of 0.7% in sulfuric acid 1 mol/DM.
Potassium armanavicius, a freshly prepared solution with a mass fraction of 0.15%.
Sodium hydroxide according to GOST 4328−77, a solution with a mass fraction of 20%. Store in a plastic container.
Carbon tetrachloride according to GOST 20288−74.
Arsenic trioxide.
The standard solutions of arsenic.
Solution A, prepared as follows: 0,1320 g of arsenic trioxide dissolved in 5 cmof sodium hydroxide solution, acidified with hydrochloric acid diluted 1:1, until an acid reaction on Congo paper. The solution was transferred into a measuring flask with volume capacity of 1000 cm
, made up to the mark with water and mix.
1 cmof solution A contains 0.1 mg of arsenic (As).
Solution B is prepared before use as follows: pipetted 10 cmof solution A in a volumetric flask with a capacity of 500 cm
, made up to the mark with water and mix.
1 cmof a solution contains 0.002 mg of arsenic (As).
(Changed edition, Rev. N 1, 3
).
2.3. Analysis
2.3.1. Weighed aluminium weighing 0.1 to 1.0 g depending on the assumed mass fraction of arsenic is placed in a beaker with a capacity of 150−250 cmand add the mixture of acids in small portions in the amount of 40 cm
. After violent reaction is over, add 5−10 cm
of sulphuric acid diluted 1:1, and the solution is evaporated to release vapors of sulfuric acid. The glass removed from the bath and after cooling, wash the walls with a little water, mix and repeat evaporation to selection of sulphuric acid fumes.
To the cooled residue salt gently while stirring add 20 cmof water, 40 cm
of concentrated hydrochloric acid and heated, without boiling, to dissolve the salts. The cooled solution was transferred to separating funnel capacity of 250 cm
, washing the walls of the glass 20 cm
of concentrated hydrochloric acid. Then add 1 cm
of potassium iodide for the recovery of pentavalent arsenic to trivalent, stirred solution and after 10 minutes, make the extraction of arsenic 20 cm
of carbon tetrachloride, shaking the contents of the funnel for 1 min.
After separation of the phases the organic phase is transferred to a second separatory funnel. In the first funnel, add 20 cmof carbon tetrachloride and repeat the extraction.
The organic phase unite in a second separating funnel and produce Stripping of trivalent arsenic 20 cmof water, shake the contents of the funnel for 1 min.
After separation of the phases carefully decanted organic phase and discarded her, and the aqueous phase transferred to a volumetric flask with a capacity of 50 cm.
Trivalent arsenic is oxidized to pentavalent, adding dropwise with stirring a solution of iodine to obtain a stable coloring of iodine. After 5 min, the excess iodine restore ascorbic acid by adding it drop by drop with stirring to the bleaching solution. Then add 10 cmof a solution of molybdate of ammonium, 5 cm
of ascorbic acid solution, 1 cm
Armenonville potassium solution, dilute to the mark with water and mix.
After 40 min, measure the optical density of the solution on the photoelectrocolorimeter or spectrophotometer, given that a maximum light absorption of the solutions corresponds to the wavelength 800 nm.
At the same time spend control experience.
Mass of arsenic is determined by calibration schedule, taking into account the amendment in the reference experiment.
(Amended And
ZM. N 3).
2.3.2. Construction of calibration curve
2.3.2.1. In a volumetric flask with a capacity of 50 cmadd from microburette 0; 2; 5; 10; 15; 20 cm
standard solution of arsenic (solution B), which corresponds to 0; 0,004; 0,010; 0,020; 0,030; 0,040 mg of arsenic, are added dropwise with stirring a solution of iodine to obtain a stable coloring of iodine. After 5 min, the excess iodine restore ascorbic acid by adding it drop by drop with stirring to the bleaching solution. Then add 10 cm
of a solution of molybdate of ammonium, 5 cm
of ascorbic acid solution, 1 cm
of a solution of potassium Armenonville and further analysis is carried out as specified in clause
Solution comparison is the solution in which arsenic was added. According to the obtained values of optical density of solutions and the known mass of arsenic build the calibration graph.
(Changed edition, Rev. N 1, 3).
2.3.2.2. (Deleted, Rev. N 1).
2.4. Processing of the results
2.4.1. Mass fraction of arsenic () in percent is calculated by the formula
where is the mass of arsenic, was found in the calibration graphics mg;
the weight of aluminium,
2.4.2. Permissible discrepancies in the results of parallel definitions should not exceed the values given in table.1.
Table 1
| Mass fraction of arsenic, % |
Allowable difference, % | |
| convergence Rel. |
reproducibility, Rel. | |
| From of 0.0004 to 0.003 incl. |
30 |
45 |
| SV. Of 0.003 «to 0.01 « |
20 |
30 |
| «0,01» 0,04 « |
15 |
25 |
(Changed edition, Rev. N 3).
3. POLAROGRAPHIC METHOD for the DETERMINATION of ARSENIC (in mass fraction of arsenic from 0.0004 inch to 0.04%)
3.1. The essence of the method
The method is based on polarography trivalent arsenic from suitably prepared solution in the voltage interval from minus 0.7 to minus 1.1 V.
3.2. Apparatus, reagents and solutions
Polarograph AC type PU-1 or similar type.
Sulfuric acid GOST 4204−77, diluted 1:2, and 3.5 mol/DMsolutions.
Nitric acid GOST 4461−77 diluted 1:1.
Hydrochloric acid of high purity according to GOST 14261−77 diluted 1:1.
The mixture of acids is prepared by mixing equal volumes of sulfuric acid diluted 1:2, hydrochloric acid, diluted 1:1 nitric acid, diluted 1:1.
Potassium iodide according to GOST 4232−74, a solution of 1 g/cm; is prepared as follows: 100 g of potassium iodide dissolved in 100 cm
of water, the solution remain in the flask of dark glass.
Sodium hydroxide according to GOST 4328−77, a solution with a mass fraction of 20%. Store in a plastic container.
Ascorbic acid, freshly prepared solution with a mass fraction of 0.5%.
Carbon tetrachloride according to GOST 20288−74.
Salesonline alum at the NTD, the solution of iron with a mass fraction of 5%; weighed 86,3 g svezheprigotovlennyj gentoomaniac alum and dissolve in water. The solution was transferred to volumetric flask with a capacity of 200 cm, made up to the mark with water and mix.
Mercury GOST 4658−73.
Arsenic trioxide.
The standard solutions of arsenic.
Solution A, prepared as follows: 0,1320 g of arsenic trioxide dissolved in 5 cmof sodium hydroxide solution, acidified at Congo paper with hydrochloric acid diluted 1:1. The solution was transferred into a measuring flask with volume capacity of 1000 cm
, made up to the mark with water and mix.
1 cmof solution A contains 0.1 mg of arsenic (As).
Solution B is prepared before use as follows: pipetted 50 cmof solution A, transferred to a volumetric flask with a capacity of 500 cm
, made up to the mark with water and mix.
1 cmof a solution contains 0.01 mg of arsenic (As).
(Changed edition, Rev. N 1,
3).
3.3. Analysis
3.3.1. Weighed aluminium weighing 0.1−0.5 g depending on the assumed mass fraction of arsenic is placed in a conical flask with a capacity of 250 cm, 30 cm, pour the
mixture of acids, close the flask watch glass.
After the violent reaction of the glass is washed with water and heated to dissolve the metal and then the solution was evaporated to release vapors of sulfuric acid. After cooling, wash the walls of the bulb a small amount of water and again evaporated to release vapors of sulfuric acid. After this, the remaining salts are dissolved in 20 cmof water and add 60 cm
of concentrated hydrochloric acid. The solution was transferred to a separatory funnel with a capacity of 250 cm
and add 2cm
of a solution of potassium iodide. Mix and allow to stand for about 10 min. Then add 15 cm
of carbon tetrachloride and gently shake the contents of the funnel for 1 min.
After settling and separation of layers poured a layer of carbon tetrachloride into another separatory funnel of the same capacity. To the water layer in the first funnel, add 10 cmof carbon tetrachloride and repeat the extraction of arsenic by shaking the funnel for 1 min. After separation of the layers attached to the layer of carbon tetrachloride, the first portion of the second funnel. The aqueous layer is discarded.
To the combined extracts of carbon tetrachloride is added 10 cmof ascorbic acid solution and produce the Stripping of arsenic by shaking the liquid for 2 min. After settling and separation of layers, the layer of carbon tetrachloride is decanted and discarded. The aqueous layer containing the arsenic was transferred in a glass with a capacity of 25 cm
, 0.15 cm added
a solution of potassium iodide and mix. Then add 0.15 cm
to 3.5 mol/DM
solution of sulphuric acid and 0.8 cm
of a solution of alum salesonline. Mix and allow to stand for 10 min. the Addition of potassium iodide, sulphuric acid and alum gentoomaniac to the prepared solutions should be made immediately in all the solutions, and sequentially, after the previous tolerancefree.
Part of the solution was transferred to a polarographic cell with Donna mercury and polarografic on polarography type AC-PPT-1 in the voltage interval from minus 0.7 to minus 1.1 V, with appropriate sensitivity of the instrument.
The top of the peak of arsenic appears when minus 0.9 V. at the same time spend control experience.
Mass of arsenic is determined by calibration schedule, taking into account the amendment kontrolnog
on experience.
3.3.2. Construction of calibration curve.
In a glass with a capacity of 50 cmand add 20 cm
of water and consistently 0, 0,5, 1,0, 1,5, 2,0, 2,5 cm
standard solution B, containing, respectively, 0,005, 0,010, 0,015, 0,020, and 0.025 mg of arsenic. The solutions were transferred to a separatory funnel, add 60 cm
of concentrated hydrochloric acid, 2cm
of a solution of potassium iodide and further analyze as described in section
According to the data obtained polarographically solutions, and the known mass of arsenic build the calibration graph.
When you replace the capillaries, you need to build a new schedule.
3.3.1,
3.4. Processing of the results
3.4.1. Mass fraction of arsenic () in percent is calculated by the formula
where is the mass of arsenic, was found in the calibration graphics mg;
the weight of aluminium,
3.4.2. Permissible discrepancies in the results of parallel definitions should not exceed the values given in table.1.
(Changed edition, Rev. N 3).
