GOST 23862.31-79
GOST 23862.31−79 Rare-earth metals and their oxides. Methods of determination of thorium and praseodymium (with Amendments No. 1, 2)
GOST 23862.31−79
Group B59
INTERSTATE STANDARD
RARE EARTH METALS AND THEIR OXIDES
Methods of determination of thorium and praseodymium
Rare-earth metals and their oxides. Methods of determination of thorium and praseodymium
ISS 77.120.99
AXTU 1709
Date of introduction 1981−01−01
The decision of the State Committee USSR on standards on October 19, 1979 N 3989 date of introduction is established 01.01.81
Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)
EDITION with Amendments No. 1, 2 approved in April 1985, may 1990 (IUS 7−85, 8−90).
This standard sets the photometric method for the determination of thorium (2·10% 1·10
%) in rare earth metals and their oxides (method I) and spectrophotometric method for the determination of praseodymium (from 1·10
% to 5·10
%) neodymium and its oxide (method II).
Method I is based on the extraction concentration of impurities of thorium 0.1 mol/DMsolution of triazolinone in carbon tetrachloride and subsequent photometric determination of thorium by the reaction with arsenazo-III. Fraction of total mass of thorium is found by the calibration schedule.
Method II is based on measurement of optical density of absorption bands of praseodymium.
(Changed edition, Rev. N 2).
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 23862.0−79.
Method I
2. APPARATUS, REAGENTS AND SOLUTIONS
Photoelectrocolorimeter FEK-60 or spectrophotometer or similar device.
Tile electric.
The chemical glasses with a capacity of 100 cm.
Volumetric flasks with a capacity of 25 and 100 cm.
Watch-glasses.
Separating funnel with a capacity of 50 cm.
Hydrochloric acid according to GOST 14261−77, H. h. or h. d. a., diluted 1:1.
Hydrogen peroxide according to GOST 10929−76.
Carbon tetrachloride according to GOST 20288−74.
Trisalicylate.
The extractant was 0.1 mol/DM(1:39) a solution of triazolinone in carbon tetrachloride.
Sulfuric acid GOST 4204−77, 0.15 mol/DMsolution.
Nitric acid of high purity according to GOST 11125−84 diluted 1:1, boiled a solution of 0.1 mol/DMsolution.
Oxalic acid according to GOST 22180−76, a solution with a concentration of 100 g/DM.
Arsenazo III solution with a concentration of 1 g/DM.
The thorium nitrate.
The solution of thorium (spare): a portion of thorium nitrate mass 0,0238 g dissolved in 0.1 mol/DMnitric acid, the solution transferred to a volumetric flask with a capacity of 100 cm
and adjusted to the mark with water.
The solution of thorium (working) containing 1 µg/cmof thorium, prepare a dilution reserve of thorium solution 0.1 mol/DM
nitric acid 100 times, prepared on the day of use.
Sec. 2. (Changed edition, Rev. N 1, 2).
3. ANALYSIS
3.1. A portion of the sample (except cerium dioxide) weighing 1 g is placed in a beaker with a capacity of 100 cm, flow 10 cm
of hydrochloric acid diluted 1:1, add a few drops of hydrogen peroxide and dissolved by heating. The solution is evaporated to dryness, the residue is dissolved in 10 cm
of hydrochloric acid diluted 1:1, and the solution transferred to a separatory funnel with a capacity of ~50 cm
, flow 10 cm
of the extractant and vigorously shaken for 2 min. After separation the aqueous phase is discarded and the organic was transferred to a clean, dry separating funnel with a capacity of 50 cm
and washed by vigorous shaking with 10 cm
of hydrochloric acid, diluted 1:1 within 2 min. the Stripping of thorium is carried out by shaking the organic layer with 10 cm
of 0.15 mol/DM
sulfuric acid for 2 min. Reextract transferred to a volumetric flask with a capacity of 25 cm
, pour 2 cm
of a solution of oxalic acid, 7 cm
of nitric acid, diluted 1:1, 1 cm
of the solution, arsenazo-III, adjusted to the mark with water and mix thoroughly.
A portion of the sample of cerium dioxide with a mass of 1 g was placed in a beaker with a capacity of 100 cm, moistened with a few drops of water, poured 10 cm
of concentrated nitric acid, 20 cm
peroksida hydrogen, stirred, closed glass watch glass and dissolved under heating. The solution is evaporated to dryness, the residue is dissolved in 10 cm
of hydrochloric acid, pour 6−8 drops of hydrogen peroxide and translate the solution into a separating funnel with a capacity of 50 cm
. Next, pour 10 cm
of the extractant, and shake the funnel vigorously for 2 min. After the delamination of the mixture aqueous phase is discarded and the organic was transferred to a clean, dry separating funnel with a capacity of 50 cm
and washed by vigorous shaking with 10 cm
of hydrochloric acid diluted 1:1 for 2 min, the Stripping of thorium is carried out by shaking the organic layer with 10 cm
of 0.15 mol/DM
sulfuric acid for 2 min. Reextract transferred to a volumetric flask with a capacity of 25 cm
, pour 2 cm
of a solution of oxalic acid, 7 cm
of nitric acid, diluted 1:1, 1 cm
of the solution, arsenazo-III, the volume was adjusted to the mark with water and mix thoroughly.
Optical density of the solution is measured on a photoelectrocolorimeter or spectrophotometer at 
The amount of thorium determined by the calibration schedule.
(Changed
I edition, Rev. N 2).
3.2. Construction of calibration curve
In a volumetric flask with a capacity of 25 cmis introduced 0,20; 0,50; 0,80; 1,2; 2,0; 5,0; 8,0; 10,0 cm
working solution of thorium (containing 1 µg/cm
of thorium), go 7 cm
of nitric acid (1:1), 2 cm
of a solution of oxalic acid, 1 cm
of the solution, arsenazo-III, made up to the mark with water and mix thoroughly.
The optical density of solutions measured on photoelectrocolorimeter or spectrophotometer at 
According to the obtained values of optical density calibration curve building, causing the y-axis the value of the optical density of the solution, and on the x — axis is the mass of thorium.
4. PROCESSING OF THE RESULTS
4.1. Fraction of total mass of thorium () in percent is calculated by the formula
where is the mass of thorium was found in the calibration schedule, mcg;
— the weight of the portion of the sample,
The result of the analysis take the average of results of two parallel measurements.
4.2. Discrepancies in the results of two parallel determinations or the results of the two tests should not exceed the values permitted discrepancies listed in the table.
| Mass fraction of thorium, % |
Allowable difference, % |
2·10 |
2·10 |
1·10 |
8·10 |
3·10 |
2·10 |
5·10 |
3·10 |
1·10 |
5·10 |
Method II
5. APPARATUS, REAGENTS AND SOLUTIONS
Spectrophotometer RI-8800 (UK) or similar device.
Tile electric.
Muffle furnace with thermostat providing temperatures up to 800 °C.
Volumetric flasks with a capacity of 10, 50, 100 cm.
Cylinder measuring with glass stopper with a capacity of 10 cm.
Watch-glasses.
Pipettes with volume capacity of 1, 2, 5, 10 cm.
Glasses glass with a capacity of 25, 50 and 100 cm.
The ash-free filter «blue ribbon».
Praseodymium oxide purity of 99.99%.
Perchloric acid, concentrated and the solution concentration of 0.01 mol/DM.
A solution of praseodymium spare, containing 10 mg/cm(based on praseodymium oxide):
500 mg of an oxide of praseodymium (pre-calcined at 800 °C) were placed in a glass with a capacity of 50 cm, moistened with water and dissolved in 5 cm
of concentrated perchloric acid at a moderate heat. The solution was transferred to volumetric flask with a capacity of 50 cm
, adjusted to the mark with water.
A solution of praseodymium prepare working dilution in 10 times a backup solution praseodymium solution of perchloric acid of concentration 0.01 mol
/DM.
5.1. Analysis
A sample of oxide of neodymium with a mass of 3 g were placed in a glass with a capacity of 50 cm, add with a pipette 2 cm
of water, 6.5 cm
of concentrated perchloric acid, the beaker cover watch glass, and dissolve first at room temperature, stirring with a glass rod, and then heated to 50−60 °C.
The solution was transferred to volumetric flask (cylinder) with a capacity of 10 cmand adjusted with water to 10 cm
.
The solution is filtered through dry filter «blue ribbon» in the dry glass. The filtrate was transferred to a cuvette optical path length of 40 mm and carry out the registration of the spectrum at fixed wavelengths of 448, 443, 438 nm; gap 2 mm; averaging time signal 5 s; number of cycles 10.
5.2. The calculation of the slope coefficient of the calibration straight
In volumetric flasks (cylinders) with a capacity of 10 cmis injected 0,1; 0,5; 2 and 10 cm
working solution containing 1 mg/cm
oxide of praseodymium, i.e., 0,1; 0,5; 2 and 10 mg of an oxide of praseodymium, adjusted to 10 cm
with a solution of perchloric acid of concentration 0.01 mol/DM
. Registration of spectra is carried out according to claim 5.1.
Slope coefficient calibration direct calculated by the formula
where — the average value of the optical density of the solution at
-the point;
— weight of an oxide of praseodymium in
-the point, mg;
4 — the number of points of the calibration straight line.
5.3. Processing of the results
Mass fraction of oxides of praseodymium () in percent is calculated by the formula
where — the average value of the optical density of the sample solution;
— slope coefficient of the calibration straight;
— the weight of the portion of the sample,
Discrepancies in the results of two parallel determinations or the results of the two tests should not exceed the values of permissible differences given in table.2.
Table 2
| Mass fraction of praseodymium, % |
Allowable difference, % |
1·10 |
0,7·10 |
2·10 |
0,8·10 |
1·10 |
0,25·10 |
5·10 |
1·10 |
1·10 |
0,15·10 |
5·10 |
0,5·10 |
Sec. 5. (Added, Rev. N 2).
