GOST 12697.2-77
GOST 12697.2−77 Aluminum. Methods for the determination of magnesium (with Amendments No. 1, 2)
GOST 12697.2−77
Group B59
INTERSTATE STANDARD
ALUMINIUM
Methods for determination of magnesium
Aluminium. Methods for determination of magnesium
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)
REPLACE GOST 12698−67 in part of sec. 2
EDITION with Amendments No. 1, 2 approved in November 1985, may 1988 (IUS 2−86, 8−88).
This standard sets the photometric and atomic absorption methods for the determination of magnesium in aluminum (with a mass fraction of magnesium from 0.001 to 0.02%).
(Changed edition, Rev. N 2).
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 12697.1−77 and GOST 25086−87.
(Changed edition, Rev. N 1, 2).
2. THE PHOTOMETRIC METHOD FOR THE DETERMINATION OF MAGNESIUM
2.1. The essence of the method
The method is based on the formation of magnesium hydroxide absorption compounds painted with fenato that photometered in 
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.
_________________
* From 1 July 2002 was put into effect GOST 24104−2001** (here and below).
** On the territory of the Russian Federation GOST R 53228−2008, here and hereafter. — Note the manufacturer’s database.
Nitric acid GOST 4461−77 diluted 1:1.
Hydrochloric acid by the GOST 3118−77, diluted 1:1, 1:3, and 0.01 mol/DMsolution.
Sulfuric acid GOST 4204−77, diluted 1:5.
A mixture of acids, is prepared as follows: mix 10 cmof nitric acid, diluted 1:1 with 300 cm
of hydrochloric acid diluted 1:3.
Iron metal obtained by the carbonyl method.
Solution of iron 1 g/l; prepared as follows: dissolve by heating 0.1 g of iron and 10 cm
of hydrochloric acid diluted 1:1 with a few drops of nitric acid and dilute with water to 100 cm
.
Sodium hydroxide according to GOST 4328−77, solutions with a mass fraction of 20%, 2% and 2 mol/DMstored in a plastic container.
The polyvinyl alcohol solution with a mass fraction of 0.5%, is prepared as follows: 1.25 g of the reagent was placed in a beaker with a capacity of 250 cm, 100 cm poured
water and heated till dissolved, the solution was filtered and after cooling dilute with water to 250 cm
.
Gelatin food according to GOST 11293−89, a solution with a mass fraction of 0.5%; prepared as follows: 100 cmof water placed in a conical flask with a capacity of 250 cm
, heated to 70 °C, poured with stirring 0.5 g gelatin and heat, stirring until dissolved. Prepare before use.
Sodium diethyldithiocarbamate according to GOST 8864−71, a solution with a mass fraction of 5%.
Phenazo, a solution with a mass fraction of 0.005% in sodium hydroxide solution 2 mol/DM.
Indicator paper Congo.
Magnesium GOST 804−93.
Solutions of magnesium standard.
Solution A, prepared as follows: 1 g of magnesium metal is dissolved in 30 cmof hydrochloric acid diluted 1:1, the solution is transferred into a measuring flask with volume capacity of 1000 cm
, is diluted to the mark with water and mix.
1 cmof the solution contains 1 mg of magnesium.
Solution B is prepared before use as follows: pipette select 5 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 0.01 mg of magnesium.
2.1, 2.2. (Changed edition, Rev. N 2).
2.3. Analysis
2.3.1. Weighed aluminium weighing 2 g were placed in a glass with a capacity of 400 cm, flow 50 cm
of sodium hydroxide solution with a mass fraction of 20% and covered with a glass watch glass. After the violent reaction is washed with glass and walls of beaker with water and heated to dissolve sample. Then pour 200 cm
of hot water, 2 cm
of the iron solution, stirred and heated to coagulate the precipitate. The warm solution was filtered through blue ribbon filter, washed the glass and wash the precipitate on the filter 5−6 times a hot solution of sodium hydroxide with a mass fraction of 2%. The filter cake is dissolved in 20 cm
hot mix of acid and the filter washed 5−6 times with hot water.
The solution collected in the beaker, which produced the dissolution, and neutralized with sodium hydroxide solution, adding it drop by drop until the purple color of paper of the Congo. The last drop of alkali is added with an interval of 20−30 C, as the color of the paper of the Congo does not change instantly. The solution was then transferred to a volumetric flask with a capacity of 100 cm, 30 cm, pour the
solution of sodium diethyldithiocarbamate, dilute to the mark with water and mix. After coagulation of the precipitate the solution is filtered through a dry filter into a dry flask with a capacity of 100 cm
. The first portion of the filtrate discarded. Pipetted 10−50 cm
of solution, depending on the expected concentration of magnesium in a volumetric flask with a capacity of 100 cm
.
Dilute the solution with water to 50 cm, pour 5 cm
of polyvinyl alcohol or gelatin solution, a pipette or from a burette, add 10 cm
, phenazo, 15 cm
of sodium hydroxide solution with a mass fraction of 20%, dilute to the mark with water and mix. Solutions, phenazo and sodium hydroxide added with stirring.
After 20 minutes, measure the optical density of the solution on the photoelectrocolorimeter or spectrophotometer, given that a maximum of light absorption of solutions corresponds to a wavelength of 560 nm.
Solution comparison is water.
At the same time spend control experience.
Mass of magnesium is determined according to the calibration schedule, taking into account the amendment in the reference experiment.
2.3.2. Construction of calibration curve
In a volumetric flask with a capacity of 100 cmpoured from microburette 0, 1, 2, 4, 6, 8, 10, 12 cm
standard solution B, which corresponds to 0, 0,01, 0,02, 0,04, 0,06, 0,08, 0,10, 0,12 mg of magnesium, dilute the solution in each flask to 50 cm
of water, pour 5 cm
of polyvinyl alcohol or gelatin solution and then act as described in section
Solution comparison is the solution, in which magnesium was not added. According to the obtained values of optical density of solutions and the known mass of magnesium to build the calibration graph.
2.3.1,
2.4. Processing of the results
2.4.1. Mass fraction of magnesium (a) in percent is calculated by the formula
where is the mass of magnesium was found in the calibration graphics mg;
— the total volume of solution, cm
;
— volume aliquote part of the solution, cm
;
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 magnesium, % |
Allowable difference, % | |
| convergence Rel. |
reproducibility, Rel. | |
| From 0.001 to 0.003 incl. |
30 |
45 |
| SV. Of 0.003 «to 0.01 « |
20 |
30 |
| «0,01» 0,02 « |
15 |
25 |
(Changed edition, Rev. N 2).
3. ATOMIC ABSORPTION METHOD FOR DETERMINATION OF MAGNESIUM
3.1. The essence of the method
The essence of the method consists in measuring the atomic absorption of a solution of aluminum containing magnesium, atomic absorption spectrometer in the flame of air — acetylene at a wavelength of RUB 285.2 nm.
3.2. Apparatus, reagents and solutions
Spectrophotometer atomic absorption model «Perkin-Elmer», «Saturn» or similar type.
Lamp hollow cathode, is intended for the determination of magnesium.
Laboratory scales according to GOST 24104−88 of the 2nd accuracy class with the weighing error of 0.0002.
Hydrochloric acid by the GOST 3118−77, diluted 1:1.
Magnesium GOST 804−93.
Acetylene dissolved technical GOST 5457−75.
Aluminum brand A995 according to GOST 11069−2001.
Mercury GOST 4658−73.
Nickel chloride according to GOST 4038−79, a solution with a mass fraction of 1%.
Stock solution of aluminium; prepared as follows: 10 g of chips of high-purity aluminium is placed in a beaker with a capacity of 600 cm, poured portions of 100−150 cm
of hydrochloric acid and add one drop of mercury or two or three drops of solution of chloride Nickel. After dissolution of the aluminum solution was evaporated to wet salts, add 200−250 cm
of water, transferred to a volumetric flask with a capacity of 500 cm
, made up to the mark with water and mix.
Solutions of magnesium standard.
Solution A, prepared as follows: 1,0000 g of magnesium metal is dissolved in 30 cmof hydrochloric acid, the solution transferred to a volumetric flask with a capacity of 1000 cm
, made up to the mark with water and mix.
1 cmof the solution contains 1 mg of magnesium (Mg).
Solution B is prepared before use as follows: 5 cmstandard solution And placed in a flask with a capacity of 500 cm
, add 10 cm
of hydrochloric acid, made up to the mark with water and mix.
1 cmof a solution contains 0.01 mg of magnesium (Mg).
(Changed edition, Rev.
N 2).
3.3. Analysis
3.3.1. Weighed aluminium weighing 1 g is placed in a beaker with a capacity of 400 cmadd 30 cm
of hydrochloric acid and dissolved, if necessary, lightly warming. The resulting solution was evaporated to wet salts loss, add 40−50 cm
of water, transferred to a volumetric flask with a capacity of 100 cm
and adjusted to the mark with water.
The obtained sample solution is sprayed into the flame atomic absorption spectrometer and measure the absorbance in the flame of air — acetylene at a wavelength of RUB 285.2 nm. Air pressure and acetylene to the design of the instrument. At the same time spend control experience. To do this in a volumetric flask with a capacity of 100 cmare placed 50 cm
basic solution of aluminum, 20 cm
of hydrochloric acid, made up to the mark with water and mix.
Mass fraction of magnesium in the sample solution and the solution of control and experience determined by the calibration schedule, which is built with every shot.
(Changed edition, Rev. N 2)
.
3.3.2. Construction of calibration curve
In a volumetric flask with a capacity of 100 cmare placed 50 cm
basic solution of aluminum and, accordingly, 0; 1; 2; 5; 7; 10; 15; 20; 25; 30; 35 and 40 cm
standard solution B, which corresponds to 0; 0,001; 0,002; 0,005; 0,007; 0,010; 0,015; 0,020; 0,025; 0,030; 0,035 and 0,040% magnesium in aluminum, adjusted to the mark with water and mix.
The prepared solutions photometrist on atomic absorption spectrometer. According to the obtained values of absorbance and known concentration of magnesium in percent build the calibration graph.
3.4. Processing of the results
3.4.1. Mass fraction of magnesium (a) in percent is calculated by the formula
where — mass fraction of magnesium in the sample, was found in the calibration schedule, %;
— mass fraction of magnesium in a control experiment, was found in the calibration schedule, %.
3.4.2. Permissible discrepancies in the results of parallel definitions should not exceed the values given in table.1.
3.4.1,
