GOST 23862.33-79
GOST 23862.33−79 Rare-earth metals and their oxides. Method for determination of silicon (with Amendments No. 1, 2)
GOST 23862.33−79
Group B59
INTERSTATE STANDARD
RARE EARTH METALS AND THEIR OXIDES
Method for determination of silicon
Rare-earth metals and their oxides. Method of determination of silicon
ISS 77.120.99
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 silicon (from 2·10% to 2·10
%) in rare earth metals and their oxides (except cerium dioxide).
The method is based on the Stripping of silicon in the form of fluoride, the formation of reduced forms of кремнемолибденовогетерополикислоты with subsequent measurement of optical density of the solution on a photoelectrocolorimeter.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 23862.0−79.
2. APPARATUS, REAGENTS AND SOLUTIONS
Photoelectrocolorimeter FEK-56 or similar.
Plastic jars with a capacity of 50 and 100 cm.
Volumetric flasks.
The PTFE cylinders with screw caps, bore 55 mm, height 60 mm.
Plastic pipette with graduations, a capacity of 5 cm.
Muffle furnace with thermostatic control, providing the temperature to 900−950 °C.
Drying oven with thermostatic control, providing the temperature to 110−120 °C.
Hydrofluoric acid according to GOST 10484−78, OS.h. 21−5.
Acid chloric, H. h, 56% solution.
Nitric acid of high purity according to GOST 11125−84; 2 mol/DMsolution.
Hydrochloric acid of high purity according to GOST 14261−77 diluted 1:1.
Boric acid, OS.h. 14−3, a saturated solution.
Ascorbic acid, a solution with a concentration of 10 g/DM(freshly made).
Ammonium molybdate according to GOST 3765−78, H. h, optionally recrystallized, solution with a concentration of 50 g/DM.
Sodium hydroxide according to GOST 4328−77, H. h, alcohol and water solutions with a concentration of 40 g/DM.
The technical rectified ethyl alcohol GOST 18300−87, higher grade, advanced double-distilled in quartz apparatus.
Potassium-sodium carbonate according to GOST 4332−76.
Silicon dioxide according to GOST 9428−73.
The water is deionized.
Standard solution silicon (spare) containing 0.2 mg/cmof silicon: 0,2139 g of silica placed in a platinum Cup, add 3−4 g of potassium carbonate of sodium, and fused in a muffle furnace at 900−950 °C until a clear melt. The smelt is leached with water, the solution was transferred to volumetric flask with a capacity of 500 cm
, the volume was adjusted to the mark with water and mix, store in a plastic container.
A solution of silicon (working) containing 10 µg/cmof silicon; prepared on the day of use by dilution of a standard solution with water to 20 times.
Sec. 2. (Changed edition, Rev. N 1, 2).
3. ANALYSIS
3.1. In the lid of the PTFE cylinder is placed 1 cmalcohol solution of sodium hydroxide, distributing it evenly, and dried in a drying Cabinet at 50−60 °C. the cylinder is placed a portion of REE oxide content of 1 g, add 2 cm
of water, 12 cm
of perchloric acid, 2, see
hydrofluoric acid, gently stirred, immediately close the cylinder cover with sodium hydroxide and kept in a desiccator at 110−120 °C for 2 h. Then the cylinder is removed from the Cabinet, gently remove the cover, to avoid contact of acids with sodium hydroxide.
(Changed edition, Rev. N 1).
3.2. When determining the mass fraction of silicon of from 2·10to 2·10
% contents cover is transferred to a polyethylene jar with a capacity of 50 cm
with a solution of boric acid (12 cm
), injected 2 cm
of a solution of nitric acid, 7 cm
of water and 2.5 cm
of a solution of molybdate of ammonium. After 15 min. poured 12 cm
of a hydrochloric acid solution, 5 cm
of ascorbic acid solution, allowed to stand for 20−30 min. the resulting solution was transferred to a volumetric flask with a capacity of 50 cm
, is diluted to the mark with water, mix and measure optical density of solution on a photoelectrocolorimeter at
Simultaneously with the analysis of the sample carried through all stages of the analysis of the audit experience of the reagents. The value of the optical density of the solution in the reference experiment must not exceed 0,15, otherwise replace the reagents.
The value of optical density in the reference experiment is calculated from the value of optical density of test solution. The amount of silicon is determined by the calibration gra
fico.
3.3. When determining the mass fraction of silicon of from 2·10% to 3·10
%, the content of the cover is transferred into a polyethylene jar with a capacity of 100 cm
with a solution of boric acid (25 cm
). Then injected 1 cm
of an aqueous solution of sodium hydroxide, 4 cm
of nitric acid solution, 20 cm
water, 5 cm
of a solution of molybdate of ammonium. After 15 min. poured 25 cm
hydrochloric acid solution, 10 cm
of a solution of ascorbic acid. After 20−30 min the resulting solution was transferred to volumetric flask with a capacity of 100 cm
, the volume was adjusted to the mark with water, mix and measure optical density of solution on a photoelectrocolorimeter at
Simultaneously with the analysis of the sample carried through all stages of the analysis of the audit experience of the reagents. The value of the optical density of the solution in the reference experiment shall not exceed 0,03, otherwise replace the reagents. The value of optical density in the reference experiment is subtracted from the value of optical density of test solution. The amount of silicon determined by calibration gr
the Afik.
3.2, 3.3. (Changed edition, Rev. N 2).
3.4. Construction of calibration curve
3.4.1. In plastic jars with a capacity of 50 cmimpose on 0,20; 0,40; 0,80; 1,20; 1,60; 2,00 cm
of a solution of silicon (containing 10 µg/cm
of silicon), pour 12 cm
of boric acid solution, 1 cm
of aqueous sodium hydroxide solution, 2 cm
of nitric acid, 7 cm
of water and 2.5 cm
of a solution of molybdate of ammonium. After 15 minutes pour in a jar of 12 cm
of a hydrochloric acid solution and 5 cm
of ascorbic acid solution. After 20−30 min, the resulting solutions are transferred to volumetric flasks with a capacity of 50 cm
, the volume of the solution was adjusted to the mark with water and mix.
The optical density of solutions measured on photoelectrocolorimeter at 
water.
3.4.2. In plastic jars with a capacity of 100 cmadministered 0,10; 0,25; 0,50; 0,75; 1,00; 1,25; 1,50 cm
standard solution silicon (containing 0.2 mg/cm
of silicon), 25 cm pour the
boric acid solution, 2 cm
of an aqueous solution of sodium hydroxide, 4 cm
of a solution of nitric acid, the volume was adjusted with water to 50 cm
, pour 5 cm
of a solution of molybdate of ammonium. After 15 min. poured 25 cm
hydrochloric acid solution, 10 cm
of a solution of ascorbic acid. After 20−30 min, the resulting solutions are transferred to volumetric flasks with a capacity of 100 cm
, the volume was adjusted to the mark with water and mix. The optical density of solutions measured on photoelectrocolorimeter at
water.
3.4.1,
3.4.3. According to the obtained values of optical density calibration graphs building, causing the y-axis the value of the optical density of the solution and on the x — axis is the mass of silicon.
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of silicon () in percent is calculated by the formula
where is the mass of silicon 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 silicon, % |
Allowable difference, % |
2·10 |
2·10 |
2·10 |
5·10 |
3·10 |
5·10 |
