GOST 23862.29-79
GOST 23862.29−79 Rare-earth metals and their oxides. Method for the determination of molybdenum (with Change No. 1)
GOST 23862.29−79
Group B59
INTERSTATE STANDARD
RARE EARTH METALS AND THEIR OXIDES
Method for the determination of molybdenum
Rare-earth metals and their oxides. Method of determination of molybdenum
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 Change No. 1, approved in April 1985 (IUS 7−85).
This standard sets the photometric method for the determination of molybdenum (from 2·10
to 2%·10
% each) in rare-earth metals and their oxides (except cerium and its dioxide).
The method is based on extraction with chloroform, molybdenum (VI) complex with a 
-benzodioxepin with the subsequent Stripping of molybdenum (VI) with aqueous ammonia and the catalytic effect of Mo (VI) to the oxidation of orthoaminophenol with hydrogen peroxide. Optical density of the solution is measured on a photoelectrocolorimeter. The molybdenum content found by the calibration schedule.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 23862.0−79.
2. APPARATUS, REAGENTS AND SOLUTIONS
Tile electric.
Photoelectrocolorimeter FEK-56 or similar device.
The quartz cylinders with ground stoppers with a capacity of 15 cm
, calibrated to 5 and 10 cm.
The quartz glasses with a capacity of 15 and 5 cm.
Quartz separating funnel with a capacity of 50 cm.
Pipettes with a capacity of 1 cm.
Before working utensils thoroughly washed distilled with sulphuric acid diluted 1:1, rinsed with double-distilled water, placed in a beaker with a capacity of 100 cmand kept in boiling water for 30−40 min.
Paper universal indicator.
Hydrochloric acid by the GOST 3118−77, H. C., 0.1 mol/DMsolution.
Sulfuric acid GOST 4204−77, H. h, distilled in quartz apparatus (selected middle fraction), diluted 1:1 and 5 mol/DMsolution.
The aqueous ammonia of high purity according to GOST 24147−80, 3 mol/DMsolution.
Salt dinatria Ethylenediamine-N, N, N', N'-tetraoxane acid, 2-water (Trilon B) according to GOST 10652−73, H. h, 0.05 mol/DMsolution.
Sodium hydroxide according to GOST 4328−77, H. h, 0.05 mol/DMsolution.
Buffer solution pH 5.0 300 cmof acetic acid are placed in a quartz flask with a capacity of 800 cm, flow portions 200 cmof sodium hydroxide solution, stirred.
Hydrogen peroxide according to GOST 10929−76, H. h, 3% solution: 10 cmof hydrogen peroxide is placed in a volumetric flask with a capacity of 100 cm, adjusted to the mark with water, mix; prepared on the day of use.
Orthoaminophenol, h, 0.1 mol/DMsolution: 0,253 g of the drug placed in a quartz cylinder with a capacity of 35−40 cm, 25 cm pour thehydrochloric acid solution, stirred; prepared on the day of use.
Chloroform, h. e. a., double-distilled in quartz apparatus, selected middle fraction.
-benzoyloxy, h. e. a., the solution in chloroform with a concentration of 4 g/DM.
Ammonium molybdate according to GOST 3765−78, h.d. a.
A standard solution of molybdenum (spare) containing 1 mg/cmof molybdenum: 1,840 g of ammonium molybdate was placed in a quartz glass with a capacity of 100 cm, is dissolved in water. The beaker content was transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water, mix.
1 cmof the solution contains 1 mg of molybdenum.
The molybdenum solution containing 0.1 mg/cmof molybdenum, prepared by successive dilution with water reserve solution 1000 times.
Sec. 2. (Changed edition, Rev. N 1).
3. ANALYSIS
3.1. A portion of the sample weighing 0.5 g was placed in a quartz glass with a capacity of 50 cm, moistened with water, poured 5 cm5 mol/DMsolution of sulphuric acid, dissolved by heating, cooled. The beaker content was transferred to separating funnel was adjusted with water to a volume of 10 cm, pour 2 cmof solution -benzoyloxy, 8 cmof chloroform and shake for 3 min. the Organic phase was collected in a quartz beaker, and the aqueous phase is performed twice extraction of molybdenum for 3 min, adding each time 2 cmof the solution -benzoyloxy and 5 cmof chloroform. The combined organic phase was transferred to a separating funnel, poured 5cmof water, 1 cmof ammonia solution and shaken for 2 min. the Organic phase was separated, the aqueous phase poured dropwise 5 mol/DMsulfuric acid to pH-5 (for universal indicator paper) content is transferred in a quartz cylinder with a capacity of 15 cm, adjusted with water to a volume of 10 cm, mix.
From the resulting solution taken 1 cmin a quartz cylinder with a capacity of 15 cm, add 1 cmof solution Trilon B, 1 cmbuffer solution, 0.2 cmof hydrogen peroxide solution, 1 cmof a solution of orthoaminophenol, adjusted with water to a volume of 5 cm, mix. The cylinders with the solutions immersed in a boiling water bath for 2 min, then quickly cooled to room temperature. The optical density of test solution is measured on photoelectrocolorimeter at 
490 nm in a cuvette with the thickness of the light absorbing layer 10 mm. as a solution comparison, use water.
Simultaneously with the samples through all stages of the analysis carried out control experience in chemicals. The value of the optical density of the solution in the reference experiment is subtracted from the value of optical density of test solution and according to the obtained value of the optical density find the mass of molybdenum in graduer
ovocna schedule.
3.2. Construction of calibration curve
3.2.1. Quartz separating funnel introduced 1, 2, 3, 4, 5, 10 cmof a solution of molybdenum (containing 0.1 µg/cmmolybdenum), pour 5 cm5 mol/DMsulfuric acid solution, adjusted with water to 10 cm, pour 2 cmof solution -benzenamine, 8 cmof chloroform and shake for 3 min. the Organic phase was collected in a quartz beaker, and the aqueous phase is performed twice extraction of molybdenum for 3 min, adding each time 2 cmof the solution -benzoyloxy and 5 cmof chloroform. The combined organic phase was transferred to a separating funnel, poured in 5 cmwater, 1 cmof ammonia solution, shaken for 2 min. Organic phase is separated. To the aqueous phase poured dropwise 5 mol/DMsulfuric acid to pH-5 (for universal indicator paper), transfer the contents in the quartz cylinder, was adjusted with water to a volume of 10 cm, mix. In one of the separatory funnels introduce all reagents except molybdenum (zero solution).
From the obtained solutions are selected at 1 cmin a quartz cylinder, and add 1 cmof solution Trilon B, and 1 cmbuffer solution, 0.2 cmof hydrogen peroxide solution, 1 cmof a solution of orthoaminophenol, adjusted with water to a volume of 5 cm, mix. The cylinders with the solutions immersed for 2 min in a boiling water bath and then quickly cooled to room temperature. The optical density of solutions measured on photoelectrocolorimeter at 
490 nm in a cuvette with the thickness of the light absorbing layer 10 mm. as a solution comparison, use water. The value of optical density of the zero solution is subtracted from the values of optical density of the solutions of the scale. The measurement was repeated five times of new portions of the solution.
According to the obtained results build a calibration curve, while the ordinate values of the optical density of the solution, and on the x — axis is the mass of molybdenum.
A separate points graphics test when analyzing samples.
4. PROCESSING OF THE RESULTS
4.1. Fraction of total mass of molybdenum (
) in percent is calculated by the formula
,
where 
is the mass of molybdenum in the sample, was found in the calibration schedule, mcg;
— the weight of the portion of the sample,
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 molybdenum, %
|
Allowable difference, %
|
2·10 |
2·10 |
1·10 |
5·10 |
2·10 |
8·10 |
