GOST 12697.7-77

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  ГОСТ 12697.7-77

GOST 12697.7−77 Aluminum. Methods for determination of iron (with Amendments No. 1, 2, 3, 4)

GOST 12697.7−77

Group B59

INTERSTATE STANDARD

ALUMINIUM

Methods of iron determination

Aluminium. Methods for determination of iron

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 27.09.77 N 2315 date of imposition established 01.01.79

Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 5−6-93)

REPLACE GOST 12703−67 in part of sec. 2

EDITION with Amendments No. 1, 2, 3, 4, approved in December 1980, November 1985, may 1987, may 1988 (IUS 3−81, 2−86, 8−87, 8−88).


This standard specifies the methods for determination of iron in aluminum: photometric (with a mass fraction of iron from 0.0004 inch to 1.0%); atomic absorption (at a mass fraction of iron from 0.005 to 1.0%).

(Changed edition, Rev. N 3, 4).

1. GENERAL REQUIREMENTS

1.1. General requirements for method of analysis according to GOST 12697.1−77 and GOST 25086−87.

(Changed edition, Rev. N 2, 4).

A. Photometric method for determination of iron

The essence of the method consists in dissolving the sample electrochemically or in hydrochloric acid, the recovery of ferric iron to ferrous with hydroxylamine, the formation of the orange complex of bivalent iron with 1,10-phenanthroline and subsequent measurement of optical density at a wavelength of 510 nm.

(Changed edition, Rev. N 3).

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.

Laboratory autotransformer (Latr), type Latr-1M or selenium rectifier, applying the electrodes of the Fisher.

Hydrochloric acid by the GOST 3118−77, diluted 1:1, 1:4, 1:2.

Hydrochloric acid of high purity according to GOST 14261−77, 4 mol/DMsolution.

Indicator paper Congo.

Ammonia according to GOST 3760−79 diluted 1:4.

Hydroxylamine hydrochloric acid according to GOST 5456−79, a freshly prepared solution with a mass fraction of 10%.

In the analysis of aluminium high-purity hydroxylamine is recrystallized, for this to rich when heated to the solution of hydroxylamine is added a double volume amount of ethanol. The formed crystals filtered and air dried between ashless filters.

Sodium acetate according to GOST 199−78 and 2 mol/DMsolution.

The technical rectified ethyl alcohol GOST 18300−87.

Orthophenanthroline, a solution with a mass fraction of 0.25% is prepared by dissolving 0.25 g of reagent in low heat in 100 cmof water.

Iron metal obtained by the carbonyl method.

Standard solutions of iron.

Solution A, prepared as follows: 0.2 g of iron was dissolved in 10 cmof hydrochloric acid diluted 1:1, the solution is transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and stirred or 0,2860 g pre-calcined at a temperature of 500−600 °C the iron oxide is dissolved by heating in 50 cmof a hydrochloric acid solution 1:1, 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 0.2 mg of iron (Fe).

Solution B is prepared before use as follows: a pipette, take 25 cmof solution A in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.05 mg of iron (Fe).

Solution; prepared before use as follows: a pipette, take 25 cmof solution A in a volumetric flask with a capacity of 1000 cm, made up to the mark with water and mix.

1 cmof the solution contains 0.005 mg of iron (Fe).

Acetic acid GOST 61−75.

Acetate buffer solution is prepared as follows: 272 g sodium acetate and dissolve in 500 cmof water, add 240 cmof acetic acid and water topped up to a volume of 1000 cm.

Nickel chloride according to GOST 4038−79, a solution with a mass fraction of 0.2%.

Mercury metal according to GOST 4658−73.

Hydrogen peroxide according to GOST 10929−76.

Iron oxide.

(Changed edition, Rev. N 1, 3, 4).

3. ANALYSIS

3.1. When the mass fraction of silicon up to 0.5% the weight of aluminum weight of 0.5−1 g were placed in a glass with a capacity of 250 cm, 30 cm, pouredhydrochloric acid diluted 1:1, and 1 cmof hydrogen peroxide solution and covered with a glass watch glass.

After the violent reaction is heated to dissolve the sample, then wash the glass and walls of beaker with water. After cooling, transfer the solution into a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix.

If the solution is turbid, it was filtered through a dry ash-free filter «blue ribbon». Reject the first portions of the filtrate, collecting the solution in a dry flask.

Pipetted 5−50 cmof solution, depending on the assumed mass fraction of iron in a volumetric flask with a capacity of 100 cm.

Dilute the solution with water to 50 cm, add 3 cmof a solution of hydroxylamine, and control the pH of the solution using indicator paper, if necessary, set the pH of the solution between 3.0 to 3.5 using ammonia solution, diluted 1:5, or a solution of hydrochloric acid diluted 1:4, then add 10 cmbuffer solution, 5 cmsolution orthophenanthroline, made up to the mark with water and mix.

After 20 minutes, measure the optical density of the analyzed solution in the spectrophotometer or photoelectrocolorimeter, given that the maximum light absorption of the solutions corresponds to a wavelength of 510 nm.

Solution comparison is water.

At the same time spend control experience. This 30 cmof hydrochloric acid diluted 1:1, and 1 cmof hydrogen peroxide evaporated to a volume of 3−5 cm, is diluted with water, transferred into a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix. Select aliquot part of the solution corresponding to aliquote part of the test solution in a volumetric flask with a capacity of 100 cmand carry out the analysis as described above.

Weight of iron is determined by the value of the optical density of the analyzed solution for the calibration schedule, taking into account the amendment in the reference experiment.

(Changed edition, Rev. N

1, 3, 4).

3.2. Upon dissolution of high purity aluminium in hydrochloric acid is used the method of electrochemical dissolution, or the method of dissolution samples of aluminium in the presence of a catalyst.

(Changed edition, Rev. N 1).

3.2.1. A sample of aluminum, made in the form of two rods, cleaned by boiling in hydrochloric acid, diluted 1:1 for 10 min. Then washed the rods with water, dried at 100 °C and after cooling weighed.

In a quartz glass with a capacity of 150 cm30 cm pour4 mol/DMhydrochloric acid solution of high purity.

The rods reinforce the holders of high-purity aluminium or titanium that are attached to the terminals Later. Then the rods are immersed in a glass of acid, include Latr in the network and dissolve the sample in the range of voltage of 10−20 V for 15 min allowed the decomposition of the sample is performed by means of the selenium rectifier, applying the electrodes of the Fisher.

During this time dissolve about 1 g of aluminum. Then Latr turned off, disconnect the rods, washed with water, dried at 100 °C and weighed.

From the difference of the masses determine the amount of soluble aluminum. The solution was evaporated to wet salts of education.

The residue is dissolved in 10 cmof water while heating to obtain a transparent solution. The solution was cooled and transferred to volumetric flask with a capacity of 25 cm. Then add 2cmof a solution of hydroxylamine, 3 cmof a solution of sodium acetate and 3 cmorthophenanthroline solution, dilute to the mark with water and mix.

Measurement of the optical density of the solution produced as described in section 3.1.

At the same time spend control experience. To do this in quartz glass with a capacity of 150 cmis placed 30 cm4 mol/DMhydrochloric acid solution, evaporated to a volume of 0.5 cm, dilute a small amount of water and transferred to volumetric flask with a capacity of 25 cm. Then the analysis is carried out as described above.

Weight of iron is determined by the value of the optical density of the analyzed solution for the calibration schedule, taking into account the amendment in the reference experiment.

(Changed edition, Rev. N 1,

3, 4).

3.2.2. Dissolution samples of aluminium in the presence of a catalyst is performed as follows: 1 g of the sample in the form of chips, pre-treated by immersion in a solution of hydrochloric acid 1:4, was dissolved in a beaker with a capacity of 250 cm, covered with watch glass, 15 cmof a hydrochloric acid solution 1:1 with the addition of 1 cmof a solution of chloride of Nickel or one drop of mercury. After dissolution, the sample solution was evaporated to a volume of 7−8 cm, is diluted with water to a volume of 50−60 cm, transferred into a volumetric flask with a capacity of 100 cmand carry out analysis as specified in paragraph 3.1.

(Added, Rev. N 1).

3.3. Construction of calibration graphs

3.3.1. Graph 1

In a volumetric flask with a capacity of 100 cmpoured from microburette 0; 0,5; 1; 2; 3; 4; 5 cmof solution B, which corresponds to 0; 0,025; 0,05; 0,10; 0,15; 0,20; 0,25; 0,30 mg of iron. Add to each flask 2 cm4 mol/DMof hydrochloric acid and dilute with water to 50 cm. Add 3 cmof a solution of hydroxylamine and control the pH of the solution using indicator paper, if necessary, set the pH of the solution between 3.0 to 3.5 using ammonia solution, diluted 1:5, then add 10 cmbuffer solution, 5 cmsolution orthophenanthroline and further analysis is carried out as specified in clause 3.1. Solution comparison is the solution in which iron was not added. According to the obtained values of optical density and known mass of iron to build the calibration graph 1.

(Changed edition, Rev. N 1

).

3.3.2. Chart 2

In a volumetric flask with a capacity of 25 cmpoured from microburette 0; 0,5; 1; 2; 3; 4 cmsolution that fits 0; 0,0025; 0,005; 0,010; 0,015; 0,020 mg of iron.

To each flask add 0.3 cm4 mol/DMhydrochloric acid solution and diluted with water to 10 cm. Add 2cmof a solution of hydroxylamine, 3 cmsodium acetate, 3 cmorthophenanthroline solution, dilute to the mark with water, mixed and further analysis is carried out as specified in clause 3.1.

Solution comparison is the solution in which iron was not added.

According to the obtained values of optical density and known mass of iron to build the calibration graph 2.

4. PROCESSING OF THE RESULTS

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

,

where is the mass of iron was found in the calibration graphics mg;

 — the total volume of solution, cm;

 — volume aliquote part of the solution, cm;

the weight of aluminium,

4.2. Permissible discrepancies in the results of parallel definitions should not exceed the values given in table.1.

Table 1

(Changed edition, Rev. N 1, 3, 4).

B. Atomic absorption method

The essence of the method consists in dissolving the samples in hydrochloric acid in the presence of hydrogen peroxide and subsequent measurement of the atomic iron absorption at a wavelength of 248.3 nm in a flame acetylene-air.

5. APPARATUS, REAGENTS AND SOLUTIONS

Atomic absorption spectrophotometer with all accessories and a radiation source for iron.

Hydrochloric acid by the GOST 3118−77, a solution of 1:1.

Acetylene in cylinders for technical GOST 5457−75.

Hydrogen peroxide according to GOST 10929−76.

Acetone according to GOST 2603−79.

Nickel chloride according to GOST 4038−79, a solution of 2 g/DM.

Aluminum with iron content not more than 0.001% in the form of chips. If necessary, shaving before use, washed with acetone, dried in a drying Cabinet at 100 °C for 2−3 min and cooled in a desiccator.

A solution of aluminum 20 g/DM: 10 g of aluminum is placed in a beaker with a capacity of 600 cm, add 300 cmof a hydrochloric acid solution and dissolved by heating, adding 1 cmof solution of chloride Nickel. The solution was cooled, transferred to a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

Iron metal in the form of wire.

Standard iron solution

Solution a: 0,1000 g of iron is placed in a tall glass with a capacity of 400 cm, flow 25 cmof water and 50 cmof a solution of hydrochloric acid, cover with watch glass and dissolved under heating by adding dropwise 0.5 cmof hydrogen peroxide solution. After dissolution the solution was heated to remove excess hydrogen peroxide, the solution was cooled, washed watch glass into the beaker, transferred to 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 iron.

Solution B: 25 cmsolution And transferred to a volumetric flask with a capacity of 250 cm, add 10 cmof hydrochloric acid, made up to the mark with water and mix. The solution is prepared before use.

1 cmof a solution contains 0.01 mg of iron.

6. ANALYSIS

6.1. A portion of the sample weighing 1.0 g was placed in a beaker with a capacity of 250 cm, flow in pieces of 30 cmof a hydrochloric acid solution. If necessary to accelerate the dissolution add 0.5 cmof a solution of Nickel chloride. Beaker cover watch glass. After the cessation of violent reaction solution is gently warmed and a few drops of hydrogen peroxide solution. After dissolution, the excess hydrogen peroxide is removed by boiling, watch glass and walls of beaker rinse with water.

If the solution is not transparent, it was filtered through a dense filter in a glass with a capacity of 250 cm. The filter cake is washed 6−8 times with hot water, collecting the washings in the same beaker.

The resulting solution, if necessary, is evaporated, cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Depending on the expected content of iron taken aliquot part of the solution according to the table.2, transferred to a volumetric flask with a capacity of 100 cm, add 10 cmof hydrochloric acid, made up to the mark with water and mix.

Table 2

Measure the atomic absorption of iron in the sample solution, the solution control experience and solutions to build a calibration curve at a wavelength of 248.3 nm in a flame acetylene-air.

The iron concentration in the sample solution and in the solution of control and experience determined by the calibration schedule.

6.2. The solution in the reference experiment is prepared according to claim 6.1, using is sample the sample the sample of aluminum with a mass fraction of iron no more than 0.001%.

6.3. Construction of calibration curve.

6.3.1. When the mass fraction of iron from 0.005 to 0.05%.

In seven volumetric flasks with a capacity of 100 cmmeasure 50 cmof solution of aluminum in six of them pour the 5.0 cmstandard solution B and 1.0; 2,0; 3,0; 4,0 and 5,0 cmstandard solution A, which corresponds to 0,05; 0,10; 0,20; 0,30; 0,40 and 0,50 mg of iron.

6.3.2. When the mass fraction of iron in excess of 0.05 to 0.5%.

In seven volumetric flasks with a capacity of 100 cmmeasured at 5 cmof a solution of aluminum 10 cmof hydrochloric acid, and then six of them poured 0,5; 1,0; 2,0; 3,0; 4,0 and 5,0 cmstandard solution A, which corresponds to 0,05; 0,1; 0,2; 0,3; 0,4 and 0,5 mg of iron.

6.3.3. When the mass fraction of iron in excess of 0.5%.

Four volumetric flasks with a capacity of 100 cmpour 2.5 cmof a solution of aluminum 10 cmof hydrochloric acid, then three of them poured 2,0; 4,0; 6,0 cmstandard solution A, which corresponds to 0,2; 0,4; 0,6 mg of iron.

Then the solutions in flasks topped up to the mark with water, mix and measure the atomic absorption of iron according to claim 6.1.

From the obtained values of atomic absorption solutions containing a standard solution, subtract the value of atomic absorption of a solution containing a standard solution, and the obtained values of atomic absorption and their corresponding grades of iron to build the calibration graph.

7. PROCESSING OF THE RESULTS

7.1. Mass fraction of iron () in percent is calculated by the formula

,

where

 — the mass of iron in the sample solution found by the calibration schedule, mg;

 — the mass of iron in solution in the reference experiment, was found in the calibration graphics mg;

 — the volume of the sample solution, cm;

 — volume aliquote part of the solution, cm;

 — the weight of the portion of the sample or the weight of the portion corresponding to aliquote part of the sample solution, g

.

7.2. Discrepancies in the results of parallel definitions should not exceed the values given in table.1.

Method B. (Introduced later, Rev. N 3).