GOST 23862.28-79
GOST 23862.28−79 Rare-earth metals and their oxides. Method of determination of molybdenum and tungsten (with Change No. 1)
GOST 23862.28−79
Group B59
INTERSTATE STANDARD
RARE EARTH METALS AND THEIR OXIDES
Method of determination of molybdenum and tungsten
Rare-earth metals and their oxides. Method of determination of molybdenum and tungsten
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 and tungsten (from 2·10
% to 3·10
% each) in rare-earth metals and their oxides (except cerium and its dioxide).
The method is based on sequential extractions with chloroform colored complex compounds of molybdenum or tungsten with ditylum with subsequent measurement of optical density of the extracts. The contents of molybdenum and tungsten find for the calibration graphs.
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.
Tile electric.
Volumetric flasks with a capacity of 100 and 1000 cm
.
Conical flasks with a capacity of 100 cm.
Pipettes with a capacity of 1, 5 and 10 cm.
Separating funnel with a capacity of 50−75 cm.
Hydrochloric acid by the GOST 3118−77, H. h, concentrated and diluted 1:2.
Sulfuric acid GOST 4204−77, H. h., diluted 1:4.
Hydrogen peroxide according to GOST 10929−76, H. h
Sodium hydroxide according to GOST 4328−77, h. e. a., 2 mol/DMsolution.
Zinc-dithiol (3, 4-dimercaptotoluene zinc salt), h. e. a., a solution with a concentration of 10 g/DM2 mol/DMsolution of sodium hydroxide, prepared the day of use.
A mixture solution of zinc-dithiol with hydrochloric acid: 300 cmof a hydrochloric acid solution, diluted 1:2, pour 25 cmof solution zinc dithiol creates a thin haze dithiol.
Carbon tetrachloride according to GOST 20288−74, h.d. a.
Hydrofluoric acid according to GOST 10484−78, H. h
Titan metal BT 1−00.
Titanium (III) sulfate solution with a concentration of 10 g/DM. 1 g of titanium metal was dissolved with heating in 100 cmof sulphuric acid, diluted 1:4 with addition of 2 cmhydrofluoric acid; prepared on the day of use.
Ammonium molybdate according to GOST 3765−78, H. h
A standard solution of molybdenum (spare) containing 1 mg/cmof molybdenum: 1,840 g of ammonium molybdate dissolved in water, the solution was transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix.
Solution of molybdenum containing 10 µg/cmof molybdenum, prepared on the day of use by dilution of a standard solution with water to 100 times.
Sodium volframovich according to GOST 18289−78.
Standard solution tungsten (spare) containing 1 mg/cmtungsten: 1,7941 volframovich g of sodium is dissolved in water; the solution is transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix.
A solution of tungsten containing 10 µg/cmof tungsten, prepared on the day of use by dilution of a backup solution with water to 100 times.
Sec. 2. (Changed edition, Rev. N 1).
3. ANALYSIS
3.1. A portion of the sample ground 1−0,1 g (depending on the content of the determined elements) is placed in a conical flask with a capacity of 100 cm, add 5 cmof concentrated hydrochloric acid, 3−4 drops of hydrogen peroxide and dissolved by heating. After complete dissolution of the sample solution is boiled until the termination of allocation of bubbles of oxygen, cooled to room temperature, add 25 cmof a mixture of solution zinc dithiol with hydrochloric acid, stirred. The solution is allowed to stand for 30 minutes, occasionally stirring. The solution was then transferred to a separatory funnel with a capacity of 50−75 cm, add 5 cmof carbon tetrachloride and extracted complex of molybdenum with ditylum by shaking the funnel for 2 min. After separation of the liquids, the organic layer was filtered through a dry filter into a cuvette with the thickness of the light absorbing layer 10 mm (water layer leave for the determination of tungsten). The optical density is measured on photoelectrocolorimeter FEK-56 at 
630 nm. As a comparison, using a solution of carbon tetrachloride. Simultaneously with the samples through all stages of the analysis carried out control experience in chemicals. The obtained value of optical density in the reference experiment is subtracted from the value of optical density of test solution. The value of the optical density of the solution in the reference experiment shall not exceed 0,03, otherwise, the reagents are replaced. A lot of find molybdenum in the calibration schedule.
3.2. Construction of calibration curve
In a conical flask with a capacity of 100 cmadministered 0,2; 0,5; 1,0; 1,5; 2,0; 2,5; 3,0 cmof molybdenum solution (containing 10 µg/cmof molybdenum), add 25 cmof a mixture of solution zinc dithiol with hydrochloric acid, stirred. The solution is kept for 30 minutes, occasionally stirring. The solution was then transferred to a separatory funnel with a capacity of 50−75 cm, add 5 cmof carbon tetrachloride and extracted complex of molybdenum with ditylum by shaking the funnel for 2 min. After separation of the liquids, the organic layer was filtered through a dry filter into a cuvette with the thickness of the light absorbing layer 10 mm and measure the optical density on the photoelectrocolorimeter at 
630 nm. As a comparison, using carbon tetrachloride.
In one of the flasks is introduced all the reagents except molybdenum solution (zero solution). The value of optical density of the zero solution is subtracted from the values of optical density of 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 the values of absorbance, and the x — axis is the mass of molybdenum in micrograms.
Individual points chart check at least once a month
.
3.3. The aqueous layer after extraction of molybdenum is placed in a conical flask with a capacity of 100 cm, is evaporated to ~10 cm, adding 25 cmof concentrated hydrochloric acid, 10 cm, solution titanium sulphate, kept in a water bath at 70−80 °C for 10 min, add 2 cmof a mixture of solution zinc dithiol with hydrochloric acid and heated for 10 min. the Solution was cooled to room temperature, transferred into a separating funnel with a capacity of 50−75 cm, add 5 cmof carbon tetrachloride and extracted complex of tungsten with ditylum, shaking the funnel for 2 min. After separation of the liquids, the organic layer was filtered through a dry filter into a cuvette with the thickness of the light absorbing layer 10 mm and measure the optical density on the photoelectrocolorimeter at 
630 nm. As a comparison, using a solution of carbon tetrachloride.
Simultaneously with the samples through all stages of the analysis carried out control experience in chemicals. The optical density of control solution should not exceed 0.02, otherwise replace the reagents.
The optical density of control solution is subtracted from the value of optical density of test solution. A lot of tungsten find for the calibration graph
.
3.4. Construction of calibration curve
In a conical flask with a capacity of 100 cmadministered 0,2; 0,5; 1,0; 1,5; 2,0; 2,5; 3,0 cmof a solution of tungsten (containing 10 µg/cmof tungsten), add 25 cmof concentrated hydrochloric acid, 10 cmof the titanium sulfate solution, incubated in a water bath at 70−80 °C for 10 min. Then add 2 cmof a mixture of solution zinc dithiol with hydrochloric acid and heated for another 10 min. the Solution was cooled to room temperature, transferred into a separating funnel with a capacity of 50−75 cm, add 5 cmof carbon tetrachloride and extracted complex of tungsten with ditylum by shaking the funnel for 2 min. After separation of the liquids, the organic layer was filtered through a dry filter into a cuvette with the thickness of the light absorbing layer 10 mm and measure the optical density on the photoelectrocolorimeter at 
630 nm. As a comparison, using a solution of carbon tetrachloride.
In one of the flasks is introduced all the reagents except the solution of tungsten (zero solution). The value of optical density of the zero solution is subtracted from the values of optical density of solutions of the scale. 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 the tungsten.
Individual points chart check at least once per month.
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of molybdenum or tungsten (
) in percent is calculated by the formula
,
where 
is the mass of molybdenum (tungsten) 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 permissible differences given in table.
| |
|
Mass fraction of molybdenum (tungsten), %
|
Allowable difference, %
|
2·10 |
1·10 |
5·10 |
1·10 |
3·10 |
5·10 |
