GOST 18385.6-89
GOST 18385.6−89 Niobium. Spectral method of determination of tungsten and molybdenum
GOST 18385.6−89
Group B59
STATE STANDARD OF THE USSR
NIOBIUM
Spectral method of determination of tungsten and molybdenum
Niobium. Spectral method for the determination of the tungsten, molybdenum
AXTU 1709
Valid from 01.01.91
before 01.01.96*
_______________________________
* Expiration removed
Protocol 5−94 N Interstate Council
for standardization, Metrology and certification
(IUS N 11/12, 1994). — Note the manufacturer’s database.
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of metallurgy of the USSR
DEVELOPERS
A. V. Elyutin, L. N. Filimonov, A. A. Nikitin, V. G., Miskaryan, S. E. Blinov, A. S. Terekhov
2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from
3. INTRODUCED FOR THE FIRST TIME
4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
Item number |
| GOST 3118−77 |
Sec. 2 |
| GOST 3773−72 |
Sec. 2 |
| GOST 4145−74 |
Sec. 2 |
| GOST 10691.1−84 |
Sec. 2 |
| GOST 18300−87 |
Sec. 2 |
| GOST 18385.0−79 |
1.1 |
| THAT 6−09−397−75 |
Sec. 2 |
| THAT 48−19−134−85 |
Sec. 2 |
This standard establishes a spectral method for the determination of tungsten and molybdenum from 0.002 to 0.05%.
Method is based on the intensity of spectral lines of tungsten and molybdenum from their mass fractions in the analyzed sample in the excitation spectrum in the arc DC.
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 18385.0*.
______________
* On the territory of the Russian Federation GOST 18385.0−89. — Note the manufacturer’s database.
2. APPARATUS, MATERIALS AND REAGENTS
The diffraction spectrograph DFS-13 with a grating 1200 lines/mm (complete installation with a universal tripod mount and being a condenser).
A constant current source, providing power not less than 260 V and a current of 20 A.
Oven muffle.
Microphotometer type MF-2 or similar type.
Cup platinum, quartz or lundbye.
Analytical scale.
Libra torsion.
A device for sharpening graphite electrodes.
Mortar and pestle agate or niobium.
The mortar and pestle Plexiglas.
Graphite electrodes of high purity 7−3 mark with a diameter of 6 mm with a recess with a diameter of 4 mm and a depth of 3 mm (lower).
Electrodes of graphite brand high purity 7−3 6 mm in diameter, sharpened to a cone with ground diameter of 1 mm (top).
Photographic plates 9x12 cm type II or equivalent, providing normal blackening of analytical lines.
Silver chloride, H. h
Potassium sulfate according to GOST 4145, O. S. h
Tungsten (VI) oxide on the other 6−09−397.
Molybdenum trioxide on the other 48−19−134, CH.
Niobium pentoxide (spectral pure).
Hydrochloric acid according to GOST 3118, diluted 1:1.
The developer according to GOST 10691.1.
Fixer: sample chernovetskogo sodium weight of 300 and 20 g of ammonium chloride according to GOST 3773 dissolved in 700 and 200 cmof water respectively, the resulting solutions were poured and the total volume was adjusted to 1 DM
.
The technical rectified ethyl alcohol according to GOST 18300.
3. PREPARATION FOR ASSAY
3.1. Preparation of a primary reference sample (OOS) containing 1% molybdenum and 1% tungsten (calculated as mass fraction of molybdenum and tungsten in a mixture of metallic niobium, molybdenum and tungsten) on the basis of niobium pentoxide. Sample of niobium pentoxide by mass 2,8038 g 0,0300 g of an oxide of molybdenum and 0,0252 g of an oxide of niobium tungsten is ground in a mortar under a layer of alcohol for 1.5−2 hours (consumption of alcohol per one operation by 30 cm). The mixture is dried under an infrared lamp to constant weight.
3.2. Sample preparation comparison (OS)
The comparison samples prepared from the primary reference sample serial dilution of the niobium pentoxide containing no molybdenum and tungsten (purity of the basis for the preparation of samples of the comparison is controlled by the spectral method (method supplements)), grinding the mixture in a Styrofoam mortar under a layer of alcohol for 1.5−2 hours (consumption of alcohol in a single operation 30 cm) and dried under an infrared lamp to constant weight. Mass fraction of molybdenum and tungsten in the samples comparison (%), calculated on the metal content of a mixture of metals (with the weight of the mixture of metals 2 g) and added to the mixture sample of niobium pentoxide and diluted sample are shown in table.1.
Table 1
| The designation of the reference sample | The mass fraction of each admixture, % | The mass of charge, g | |
| niobium pentoxide |
dilute sample | ||
| OC1 |
0,05 |
2,7180 |
0,1430 (OOC) |
| OC2 |
0,02 |
1,7166 |
1,1444 (OC1) |
| ОС3 |
0,01 |
1,4305 |
1,4305 (OS2) |
| ОС4 |
0,005 |
1,4305 |
1,4305 (ОС3) |
| ОС5 |
0,002 |
1,7166 |
1,1444 (ОС4) |
3.3. Preparation of the buffer mixture
A buffer mixture containing 70% silver chloride and 30% potassium sulfate: grind in a mortar sample of the substances. The resulting mixture is stored in tightly closed opaque containers.
4. ANALYSIS
A portion of the chip of niobium with a weight of 0.5 g was washed with hydrochloric acid in a glass beaker by heating. The acid is drained, washed shavings with distilled water and alcohol (alcohol consumption per transaction of 3 cm). The washed chips is placed in a platinum Cup and calcined in a muffle until constant weight, gradually raising the temperature to 800 °C. From 1 g of niobium should be 1.43 g of niobium pentoxide. Received pentoxide carefully fray, taken from it weighed 200 mg and triturated in a mortar with a plexiglass mounting with a weight of 100 mg of buffer mix. The prepared sample was Packed tightly into the recesses in the three lower electrodes. The excess material projecting above the upper edge of the electrode, cleaned with a spatula. The electrode with the sample placed in the electrode holder tripod, and between these and the upper electrode of the light the arc of constant current to maintain the arc current is (15±0,5) A, the interelectrode distance should be 3 mm, exposure time — 30 sec.
The index of the scale of the wavelength of the spectrograph is mounted so that a part of the spectrum of 430 nm was in the middle of the spectrogram.
The same operations except for the conversion into the pentoxide, comply with each of the comparison samples.
5. PROCESSING OF THE RESULTS
5.1. In each of the spectrograms of photoretrieval find the blackening of analytical lines of molybdenum or tungsten () and background near the line (
) and calculate the difference pucherani (
,
,
obtained three spectrograms taken for each sample, find the arithmetic mean (
).
Analytical lines and spectral region for measurement of background given in table.2.
Table 2
| The designated element |
Range of determined concentrations, % |
Analytical line wavelength, nm |
The background spectrum, the wavelength region, nm |
| Molybdenum |
0,002−0,01 |
429,32 |
>429,32 |
| Molybdenum |
0,01−0,05 |
426,93 |
>426,93 |
| Tungsten |
0,002−0,01 |
429,46 |
<429,46 |
| Tungsten |
0,01−0,05 |
426,94 |
<426,94 |
The results of electrophoretic spectra of samples comparisons build a calibration curve in the coordinates 
is the logarithm of the mass fraction of molybdenum or tungsten in the reference sample. Mass fraction of molybdenum or tungsten in the sample find the results of the photometry of the three spectra with the help of calibration curve.
The difference between the largest and smallest results of the three parallel definitions should not exceed the allowable absolute values of the differences indicated in the table.3.
Table 3
| The designated element |
Mass fraction, % |
The absolute allowable difference, % |
| Molybdenum |
0,002 |
0,001 |
| 0,010 |
0,004 | |
| 0,050 |
0,015 | |
| 0,002 |
0,001 | |
| Tungsten |
0,010 |
0,004 |
| 0,050 |
0,015 |
If in the spectra of samples basis of comparison, there is a weak line of the element, then the construction of calibration curve, corrected for the value of the mass fraction of the element in the basis. An amendment is permissible only under the condition that this value does not exceed the specified for the method lower limit of determination.
5.2. Validation results
One of the analyzed samples check series is converted into the pentoxide (see sect.4). The sample of niobium pentoxide by weight of 0.5 g add a sample weight of 0.5 g of the second reference sample (originally found the mass fraction of molybdenum or tungsten in the analyzed sample equal to 0.01% or less) or the sample mass of 0.5 g of the first reference sample for the mass fraction of molybdenum in the analyzed sample is 0,01−0,03%. The mixture is thoroughly ground in a mortar Styrofoam under a layer of alcohol (consumption of alcohol in a single operation 3 cm), dried under infrared lamp and analyzed in sect.4, 5.
The analyses are correct, if the first mixture of the sample and additives, minus half of the original mass fraction found in the sample obtained (0,010±0,003%), and for the second mixture (0,025 ±0,005)% of molybdenum or tungsten.
If the results are outside specified limits, the control of the correctness of the results of repeat tests, increasing the number of parallel definitions up to six. The obtained average values should be: for the first mixture (0,01±0,002)%, for the second mixture (0,025±0,004)%.
