GOST 18385.3-79
GOST 18385.3−79 Niobium. Methods for determination of molybdenum (with Amendments No. 1, 2)
GOST 18385.3−79
Group B59
STATE STANDARD OF THE USSR
NIOBIUM
Methods for determination of molybdenum
Niobium. Methods for the determination of molybdenium
AXTU 1709*
______________
* Introduced advanced Edit. N 1.
Valid from 01.07.1980
before 01.07.1985*
_________________________________
* Expiration removed
Protocol 5−94 N Interstate Council
for standardization, Metrology and certification
(IUS N 11/12, 1994). — Note the manufacturer’s database.
DEVELOPED by the Ministry of nonferrous metallurgy of the USSR
PERFORMERS
A. V. Elyutin, Yu. A. Karpov, A. G. Valkanov, L. N. Filimonov, V. V. Korolev, V. V. Nedler, V. G., Miscreants, T. M. Malyutina, V. M. Mikhailov, E. G. Nembrini
INTRODUCED by the Ministry of nonferrous metallurgy of the USSR
Member Of The Board Of A. P. Snurnikov
APPROVED AND promulgated by the Decree of the State Committee USSR on standards on may 30, 1979 N 1968
REPLACE GOST 18385.4−73
MADE: the Change in N 1, approved and put into effect by the Decree of the USSR State Committee for standards from
Change N 1, 2 made by the manufacturer of the database in the text IUS N 1, 1985, IUS N 3, 1990
This standard sets the photometric method for the determination of molybdenum from 0.004 inch to 0.04%.
(Changed edition, Rev. N 2).
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 18385.0−79*.
_______________
* On the territory of the Russian Federation GOST 18385.0−89. — Note the manufacturer’s database.
2. The PHOTOMETRIC METHOD for the DETERMINATION of MOLYBDENUM (with a mass fraction of from 0.004 inch to 0.04%)
The method is based on decomposition of the sample by melting the sample with sodium hydroxide, separation of the molybdenum from the substrate processing Plava water extraction of the complex compound of molybdenum with ditylum amylacetate (or chloroform), and measuring the optical density of the extract.
Fraction of total mass of molybdenum and tungsten can be determined from alikvotnih different parts of the same sample solution.
2.1 Equipment, reagents and solutions
Type photoelectrocolorimeter FEK-60 or similar type.
Oven muffle.
Nickel crucibles.
Analytical scale.
Microburette.
Separating funnel with a capacity of 50 cm.
Pipette piston.
Volumetric flasks with a capacity of 100, 1000 cm.
Beakers capacity 50, 100, 250 cm.
Distilled water.
Molybdenum metal of high purity on the other 48−19−69−80 containing not less than 99.5% molybdenum.
Sodium hydroxide according to GOST 4328−77.
Hydrochloric acid by the GOST 3118−77.
The technical rectified ethyl alcohol GOST 18300−87.
Zinc-dithiol.
Suspension zinc dithiol: hitch zinc-dithiole a mass of 0.1 g was triturated in a porcelain mortar with a minimal amount of alcohol and diluted with the same alcohol to 25 cm. Before use the suspension was shaken.
Amyl ether acetic acid (amylacetate).
Chloroform according to GOST 20015−88.
Hydrogen peroxide according to GOST 10929−76.
Ammonia water according to GOST 3760−79.
(Changed edition, Rev. N 2).
2.2. Preparation for assay
2.2.1. Preparation of standard solutions of molybdenum
Solution of molybdenum (spare) containing 0.1 mg/cmof molybdenum: the weight of molybdenum metal weighing 0.1 g was dissolved with heating in 5−10 cmof hydrogen peroxide. Poured drop by drop ammonia to a bleaching solution, heated and boiled for a few minutes for the destruction of hydrogen peroxide. The solution was cooled, transferred to a volumetric flask with a capacity of 1 DM, adjusted to the mark with water and mix.
Solution of molybdenum (working) containing 0.01 mg/cmof molybdenum, prepared by diluting a backup solution with water in 10 times a day use.
2.2.2. Construction of calibration curve
In glasses with a capacity of 50 cmflow 0,3; 0,5; 0,7; 1,0; 1,5; 2,0 and 3.0 cmof the working standard solution of molybdenum, which corresponds to 3,0; 5,0; 7,0; 10; 15; 20 and 30 mcg of molybdenum, and top up with water to 15 cm, and then add 15 cmof hydrochloric acid and stirred. Add 2 cmof a suspension of zinc-dithiol and leave for 15 minutes, stirring. The solutions were transferred to a separatory funnel with a capacity of 50 cm, flow from microburette or pipette with the piston 5 cmof amylacetate (or chloroform), shaken for 1 min and after separation of the phases, discard the aqueous phase.
The obtained extracts are successively transferred in a dry cell of photoelectrocolorimeter with a thickness of the light absorbing layer 3 mm (weight of molybdenum in fotometriya extract more than 15 mg) or 5 mm (weight of molybdenum is less than 15 µg). Cover the cuvette with a lid, allow the extract to settle the bubbles and measure the optical density of each extract on the photoelectrocolorimeter using a filter with maximum transmittance at a wavelength of 660 nm against water.
On the found values of optical density and corresponding masses of molybdenum to build the calibration graph.
2.2.1,
2.3. Analysis
0.3−0.5 g of shavings of niobium (if the mass fraction of molybdenum, up to 0.02%, take 0.5 g, more than 0,02% — 0.3 g) was placed in a Nickel crucible, where the pre-melted with 1 g of sodium hydroxide, add 3 g of sodium hydroxide, put the crucible into the cold muffle, bring the temperature to 800−850 °C and fused to a homogeneous melt. The crucible with the melt is cooled and treated with 60 cmof water in a glass with a capacity of 150−200 cmwhen boiling.
After cooling the solution to precipitate transferred to a volumetric flask with a capacity of 100 cm, is diluted to the mark with water, mix thoroughly and leave to pursue the sediment. Take 10−15 cmof a clear solution in a glass with a capacity of 50−70 cm, dilute with water to 15 cm, flow 15 cmof hydrochloric acid, mix, pour 2 cmof a suspension of zinc-dithiol and leave for 15 minutes, stirring. The solution was transferred to a separatory funnel with a capacity of 50 cm, flow from microburette or pipette with the piston 5 cmof amylacetate (or chloroform), use the extractant that was used in the preparation of solutions of comparison, and shaken for 1 min. After the separation of the aqueous phase is discarded and the extract was transferred to a dry cuvette and measure its optical density (p.2.2.2).
Simultaneously with the analysis under the same conditions by two parallel control experience. Optical density of the solution in the reference experiment should not exceed 0.01. From the values of absorbance of the analyzed solution is subtracted the average value of the optical density of the solution in the reference experiment.
The mass of molybdenum in the solution found by the calibration schedule.
(Changed edition, Rev. N 1).
2.4. Processing of the results
2.4.1. Mass fraction of molybdenum in the sample () in percent is calculated by the formula
,
where — weight of molybdenum, was found in the calibration schedule, mcg;
— volume aliquote part, cm;
— the weight of the portion,
The difference between the results of two parallel definitions and results of the two tests shall not exceed the allowable absolute values of the differences indicated in the table.1.
Table 1
Mass fraction of molybdenum, % | Allowable absolute differences, % |
0,004 | 0,001 |
0,01 | 0,002 |
0,02 | 0,003 |
0,04 | 0,005 |
Allowable absolute difference for the intermediate mass fraction of molybdenum calculated using linear interpolation.
2.4.2. Validation results
The correctness of the results of analysis control method supplements. Three Nickel crucible placed in 1 cmcore solution (0.1 mg of molybdenum) and evaporated to dryness with gentle heating. In each crucible add 1 g of sodium hydroxide, heated to melt and injected 0.5 g of the niobium mass fraction of molybdenum in running PP.2.3; 2,4, and makes up about 0.02%. Added to the crucibles with 3 g of sodium hydroxide, placed in a muffle and then analyzed on PP.2.3; 2.4.
For the result of the analysis of the sample with the addition of be the arithmetic mean of the three obtained results of single determinations. The found value of the additive — difference between the result of the analysis of the sample with the additive and initially received by result of analysis of the same sample without additives should be in range (0,0200±0,0025)%.
If the found value supplements out of the specified range, control the correctness of the results again, increasing the number of batches to six and getting the result of the analysis of the sample with the additive as the arithmetic mean of the six results of single determinations. Found the value of supplements should be in range (0,0200±0,0021)%.
2.4.1,
Section 3. (Deleted, Rev. N 2).