GOST 23862.35-79
GOST 23862.35−79 Rare-earth metals and their oxides. Methods of determination of sulphur, zinc, cerium, and europium (with Amendments No. 1, 2)
GOST 23862.35−79
Group B59
INTERSTATE STANDARD
RARE EARTH METALS AND THEIR OXIDES
Methods of determination of sulphur, zinc, cerium and europium
Rare-earth metals and their oxides. Methods of determination of sulphur, zinc, cerium and europium
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 Amendments No. 1, 2 approved in April 1985, may 1990 (IUS 7−85, 8−90).
This standard specifies methods polarographic determination of sulphur (5·10% to 2·10
%), zinc (5·10
% 1·10
%) and europium (from 1·10
% 1·10
%) in rare earth metals and their oxides (except cerium and its dioxide), and voltammetric determination of cerium dioxide to the oxides of lanthanum and europium (5·10
% 1·10
%) and in the oxides of yttrium and neodymium (1·10
% 1·10
%).
(Changed edition, Rev. N 2).
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 23862.0−79.
SULFUR DETERMINATION
The method is based on the Stripping of sulfur in the form of hydrogen sulphide, the absorption solution of hydroxylamine hydrochloric acid and ethylenediaminetetraacetic acid in the potassium hydroxide with subsequent polarographic determination.
(Changed edition, Rev. N 1).
2. EQUIPMENT, REAGENTS, SOLUTIONS
Polarograph PPT-1, PU-1 or similar device.
Installation for dissolution of samples and recovery of sulfur (see the devil.1).
Damn.1
Chemical glass with a capacity of 2000 cm.
A Buchner Funnel.
Volumetric flasks with a capacity of 50, 100, 1000 cm.
The gaseous nitrogen according to GOST 9293−74.
Filters «white ribbon».
Bidistilled water: distilled water is poured into the flask of the distillation apparatus with a capacity of 2000 cm, is poured 1 g of potassium hydroxide and potassium permanganate to the intense coloration and boil it. Collect the middle fraction equal to 1/3 of the total volume of the distillate, the first and third fractions discarded.
Sodium posterolaterally (hipofosfit sodium) according to GOST 200−76, H. h
Potassium permanganate according to GOST 20490−75.
Pyrogallol And h.d. a.
Potassium hydroxide according to GOST 24363−80.
Hydroxylamine hydrochloride according to GOST 5456−79, h.d. a.
Potassium dichromate according to GOST 4220−75, h.d. a.
Potassium chloride according to GOST 4234−77, h. e. a., a saturated solution.
Sodium sulfide (sodium sulfide) according to GOST 2053−77.
Hydrochloric acid by the GOST 3118−77, H. h, concentrated.
Itestosterone acid according to GOST 4200−77.
Acetic acid GOST 61−75, 1 mole/DMsolution.
Sulfuric acid GOST 4204−77, 0.05 mol/DM(fixanal).
Ammonia water according to GOST 3760−79, 25% solution, OS.h.
Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid, 2-water (Trilon B) according to GOST 10652−73: 500 g Trilon B pour 300 cmof distilled water. Add ammonia until complete dissolution of the precipitate. The solution is filtered through a dense filter. Add 6 mol/DM
hydrochloric acid to neutralize the solution (on the paper of the Congo) and an excess of 100 cm
. Filtered through a Buchner funnel. Precipitate was washed 10 times with cold double-distilled water. Trilon B, the resulting precipitate is air dried.
Solution a: potassium hydroxide 2 mol/DMsolution in svejeprokipachenna the double-distilled water containing 10 g Trilon B in 100 cm
, is prepared two days before consumption.
Solution B: 2 mol/DMsolution of hydrochloric acid hydroxylamine.
Polarographic background: 80 cmof solution A, 20 cm
of solution B and 150 cm
svejeprokipachenna double-distilled water mixed in a day of use.
Recovery blend: a mixture of 300 cmof concentrated hydrochloric and 500 cm
itestosterone acids, 150 g of hypophosphite of sodium and 200 cm
of distilled water, boiled for 6−8 hours to install with a reflux condenser with constant purging with nitrogen at a speed of 3−4 bubbles per second. The nitrogen is purified by passing through two bottles of Drexel with a solution of pyrogallol with a concentration of 250 g/DM
solution of potassium hydroxide (250 g/DM
). During cooling from the recovery of the mixture should stand out of the salt (lack of salts indicates the lack of concentration of hydrochloric acid). Recovery drained mixture with salt and store in a flask with a glass stopper in the dark place.
Chromate of lead is precipitated on asbestos: 500 cm2 mol/DM
solution of acetate of lead is poured on 500 cm
of 0.5 mol/DM
solution of potassium dichromate in 1 mol/DM
acetic acid in the presence of 200 g of chopped asbestos cord, pre-swollen while maintaining for 1 h in a hot solution of potassium dichromate in acetic acid.
The asbestos and the precipitate of chromate of lead separated by filtration through a Buchner funnel, washed 20 times with distilled water and calcined (after separation from the filter) in a porcelain Cup in a muffle furnace at 500−550 °C for 4 h. the Sintered asbestos with precipitated chromate of lead is ground after cooling and stored in a sealed bottle.
Standard solution of sulphate sulphur (alternate): (6,25±0,05) cm0.05 mol/l
sulfuric acid solution, prepared of fiksanala, diluted with double-distilled water to 100 cm
in a volumetric flask; 1 cm
contains 100 micrograms of sulfur.
Standard solution of sulphate sulphur (operating): 10 cmfallback solution of sulphate sulphur is diluted with double-distilled water to 100 cm
in a volumetric flask; 1 cm
contains 10 µg of sulfur, prepared on the day of use.
A standard solution of sulfide sulfur (main): crystal of sodium sulfide with a weight of about 20 mg of dried filter paper and accurate weighing on an analytical balance class And determine its mass in mg, and then dissolved in a volumetric flask with a capacity of 100 cm
in 20 cm
polarographic background and the volume was adjusted solution to the mark with double-distilled water svejeprokipachenna; prepared on the day of use.
A standard solution of sulfide sulfur (work): 748/ml of primary solution was diluted in a volumetric flask polarographic background to 100 cm
. Stock solution was measured with a burette with an error of not more than 0.05 cm
. 1 see
the working solution contains 10 µg of sulfide sulfur; prepared immediately before use.
Sec. 2. (Changed edition, Rev. N 1, 2).
3. PREPARATION FOR ASSAY
3.1. Check the correct operation of the installation
Installation collect. In bubblers 11, 12, and 10 is poured a solution of pyrogallol in the solution of potassium hydroxide. 9 in the bubbler, pour the double-distilled water. Quartz tube 7 is filled with chromate of lead deposited on the asbestos, and placed in a tube furnace 8. 9 connect the bubbler with the bubbler 10 and the reaction flask 5 (quartz or glass) with vinyl chloride hoses. The other connection is carried out using rubber hoses. The temperature of the tubular furnace 8 kept from 550 °C to 600 °C. In the flask 5 is filled 150 cmpre-treated recovery of the mixture, and the receiver 1−10 cm
polarographic background. Using a reverse refrigerator 2 pass cold water. Socket refrigerator 2 and the socket tube 3 is rubbed spectral pure graphite. Through the installation of flow a stream of nitrogen at a speed of 15−25 bubbles in the receiver for 10 seconds On the tightness of the installation is judged by the coincidence of the velocity of nitrogen bubbles in the bubbler 12 and the receiver 1.
Through the socket tube 3 by means of capillary pipette is introduced into the reaction flask 0.2 cmof the working standard solution of sulphate sulphur. Include a hot plate 6. Power tiles is adjusted so that the solution in the flask was boiled for 10−15 min., the hydrogen Sulfide is distilled for 35−40 min. from power on electric. After distilling off the hydrogen sulphide determine the sulfur content in the receiver. For this purpose a solution from the receiver poured into the low impedance of the polarographic cell with an external anode (anode compartment is filled with saturated solution of potassium chloride) and remove polarogram solution in the range of potentials from minus 0.4 to minus 0.9 V. the peak Potential of sulfide ion about minus 0.8 V relative to the saturated calomel electrode. Due to diffusion of sulfide ions in the anode compartment of the electrolytic potential of the peak may gradually move in a positive direction. So everyday you need to recharge the anode compartment of a cell a fresh saturated solution of potassium chloride. The peak height of sulfur is determined, calculating the arithmetic mean value of the difference of the ordinate of a point high on polarogram and horizontal platforms at the base of the peak from the positive potentials (or at least on the same side) and the difference of the ordinates of the points of maximum and minimum at the negative peak branch.
The height of the peak on polarogram solution in the receiver is compared with the height of the peak solution of 2 µg of sulfide sulfur in 10 cmsolution (to obtain this solution, 0.2 cm
of the working standard solution of sulfide sulfur was diluted in a narrow graduated cylinder polarographic background up to 10 cm
). The difference of the heights of both peaks shall not exceed 10% relative to the height of the peak for the standard solution of sulfide sulfur. Otherwise check up tightness of installation, the fridge washed with double-distilled water and repeat the definition. The completeness of the distillation of sulfur check before starting work.
3.2. The control experience
A control experiment is conducted omitting the nitrogen recovery through boiling the mixture for 30 min. the Value in the reference experiment (in g of sulfur in 10 cm) is determined by the ratio of the height obtained when polarographically solution in the receiver, the height of the peak obtained in the recovery of 2 mg of sulphate sulphur. If polarogram solution in the control experiment did not observe the peak of sulfur, and there is a inflection point on a polarographic curve at the potential of peak sulfur, the wave height and take half the difference of the ordinates of inflection points and minima on the positive branch of the peak.
The installation think is workable if the value of the reference experience not more than 0.05 mg of sulfur. The value of the reference experience check every day before starting work and after each transition from the distillation of large quantities of sulfur to small.
3.3. The calibration of the device
For calibration of the unit carried out the recovery and Stripping of sulfur from 0.1−0.2 cmworking standard solution of sulphate sulphur as specified in claim 3.1. The instrument is calibrated one to two times a day.
4. ANALYSIS
4.1. 150 cmpre-treated recovery of the mixture is poured in the reaction flask 5. After establishing the completeness of the distillation of sulfur according to claim 3.1 and check the value of the reference experiment according to claim 3.2 regenerative mixture in the reaction flask is cooled down. In the receiver 1 is filled with a new portion (10 cm
) polarographic background, and into the reaction flask with a restorative mixture was placed weighed test portion weigh about 0,5−2 g, depending on the sulfur content. Dissolution and recovery of sulfur compounds are restorative boiling mixture for 30 min in nitrogen flow. After the dissolution and recovery determine the sulfide sulfur in the solution in the receiver.
One portion of the recovery mixture (150 cm) can sequentially analyze several batches of the oxide of re, while their weight does not exceed 10 g.
5. PROCESSING OF THE RESULTS
5.1. Mass fraction of sulfur () in percent is calculated by the formula
where is the mass of sulfur in the standard solution injected to calibrate the instrument, µg;
— the height of the peak obtained after injection of the sample, mm;
— the height of the peak obtained in a control experiment, mm.
— the height of the peak obtained during the calibration of the device, mm;
— the weight of the portion of the sample,
All the high peaks to calculate the results of polarographic determination of sulfur converted to the same instrumental sensitivity polarograph.
The result of the analysis take the average of results of two parallel measurements.
5.2. Discrepancies in the results of two parallel determinations or the results of the two tests should not exceed values of allowable differences specified in table.1.
Table 1
| Mass fraction of sulfur, % | Allowable difference, % |
5·10 |
3·10 |
1·10 |
5·10 |
1·10 |
3·10 |
2·10 |
4·10 |
6. DETERMINATION OF ZINC
The method is based on the polarographic determination of zinc in ammonium chloride solution on dripping mercuric electrode at a potential of about minus 1.3 V relative to the bottom of mercury.
(Added, Rev. N 1).
6.1. Apparatus, reagents and solutions
Polarograph oscilloscope OP-5123−0.3 mm, PU-1 or similar with mercury dripping electrode and electrolytic cell polarography Donna a mercury anode.
Analytical scale.
Tile electric.
Glasses chemical glass with a capacity of 50 cm.
Pipettes with a capacity of 1, 2, 5, 10 cm.
Measuring cylinders with a capacity of 100 cm.
Volumetric flasks with a capacity of 100, 1000, and 2000 cm.
Filters «white ribbon».
Hydrochloric acid by the GOST 3118−77, H. h and diluted (1:1).
Ammonia water according to GOST 3760−79, H. h
Sodium sanitarily according to GOST 195−77, h. e. a., a solution with a concentration of 200 g/DM.
Gelatin food according to GOST 11293−89, a solution with a concentration of 20 g/DM.
Mercury brands r0 according to GOST 4658−73.
Zinc GOST 3640−94, h.d. a.
Distilled water GOST 6709−72.
Ammonium-chloride background is prepared as follows: into a measuring flask with a capacity of 2000 cm600 cm pour
distilled water 333 cm
of concentrated hydrochloric acid, cautiously add 666 cm
of water of ammonia and 333 cm
solution semitecolo sodium with a concentration of 200 g/DM
, adjusted with distilled water to the mark, stirred and cooled.
Standard solution of zinc (spare) containing 1 mg/cmzinc: 1.0 g of zinc is dissolved in 40 cm
of hydrochloric acid (1:1) under heating and the solution was transferred into a measuring flask with volume capacity of 1000 cm
, the volume was adjusted solution with distilled water to the mark and mix.
Standard solution of zinc (working) containing 0.1 mg/cmzinc: aliquot part of a backup solution zinc volume of 10 cm,
transferred to a volumetric flask with a capacity of 100 cm
, the volume was adjusted solution with distilled water to the mark and mix.
(Amended And
ZM. N 1, 2).
6.2. Analysis
6.2.1. A portion of the sample weighing 0.2 g was placed in a beaker with a capacity of 50 cm, moistened with distilled water, add 5 cm
of hydrochloric acid (1:1) and dissolved by heating. The solution is evaporated to wet salts, salt dissolved in 5−10 cm
of distilled water and transferred into a flask with a capacity of 100 cm
, which was pre-administered to 60 cm
of ammonium-chloride background and bring to the mark with distilled water. When using polarography DC in the flask before bringing the solution volume to the mark with water, add 5 cm
of the gelatin solution and mixed. After 20 min the solution was filtered from the precipitate of the hydroxide through the filter «white ribbon» is placed in the cell and polarographic. Polarographically solution are in an electrolysis cell with mercury and Donna with the use of a dripping mercury electrode in the range of potentials from minus 1.0 to minus 1.5 V. the peak Potential of zinc is about negative 1.3 V. Polarogram of each solution is removed three to four times. The height of the peak of zinc measured vertically, is drawn through the top of the peak to the intersection with a tangent connecting the bases of the branches peak.
When using the oscilloscope polarograph polarography is carried out in a mode of differential polarography, the rate of sweep voltage of 0.25 In/sec.
Simultaneously with the samples through all stages of the analysis carried out control experience in chemicals. The correction control experience should not be more than 0.05 mg, otherwise change the reagents.
Mass fraction of zinc in the sample find for the calibration schedule.
6.3. Construction of calibration curve
In a volumetric flask with a capacity of 100 cmpour 0; 0,2; 0,5; 1; 2 cm
of a working solution of zinc with a concentration of 0.1 mg/cm
, which corresponds to 0; 0,02; 0,05; 0.1 and 0.2 mg of zinc. To each flask add 60 cm
of ammonium-chloride background and then do the same as in the determination of zinc in a sample according to claim 6.2.1, the volume was adjusted to the mark with water, mix and polarographic. Build a calibration curve, causing the x-axis the amount of zinc in mg per 100 cm
of solution, and on the y — axis the corresponding value in millimeters of the heights of peaks of zinc.
6.4. Processing of the results
6.4.1. Mass fraction of zinc () in percent is calculated by the formula
where is the mass of zinc that was found in the calibration graphics mg;
— the weight of the portion of the sample,
All the high peaks to calculate the results of polarographic determination of zinc count on one instrumental sensitivity.
The result of the analysis take the average of results of two parallel measurements.
6.4.2. Discrepancies in the results of two parallel determinations or the results of the two tests should not exceed the values of permissible differences given in table.2.
Table 2
| Mass fraction of zinc, % |
Allowable difference, % |
5·10 |
3,0·10 |
2·10 |
4,0·10 |
5·10 |
6,3·10 |
1·10 |
1,7·10 |
6.2
7. DEFINITION OF CERIUM
The method is based on electrochemical pre-concentration of cerium in the form of fitata cerium (IV) on the surface of the graphite electrode and subsequent voltampermetric the determination of cerium during the cathodic scan of the polarization voltage.
(Added, Rev. N 1).
7.1. Apparatus, reagents and solutions
Polarograph PU-1−5122 or equivalent with a graphite electrode and an electrolytic cell with an external anode.
The electrolytic bridge.
The saturated calomel electrode.
The magnetic stirrer.
Analytical scale.
Installation for impregnation of graphite electrodes (Fig.2).
1 — hot plate; 2 — Cup capacity of 500 cm, filled with glycerin on a half of volume; 3 — a thick-walled glass tube with a diameter of 30−40 mm, the curved angle of 100−120°, the length of the horizontal part of 100−150 mm, the length of the vertical part is 200−300 mm; 4 — tripod 5 — hollow tube with socket and outlet tube to the vacuum pump (the cone and the tube has a hole with a diameter of 3−4 mm)
Damn.2
Forevacuum pump 2НВР-5D or similar.
Tripod laboratory.
A spirit lamp laboratory according to GOST 25336−82.
Drying Cabinet.
Filter paper.
Emery cloth sanding paper, waterproof according to GOST 10054−82.
Tile electrical power of 600 watts.
Muffle furnace with thermostat, providing a temperature of 900 °C.
The machine tool for sharpening of electrodes.
Polyethylene film according to GOST 10354−82.
Tubes, glass, with a length of 100−110 mm with an inner diameter of 3−4 mm.
The low density polyethylene according to GOST 16338−85.
The oil and solid paraffin according to GOST 23683−89.
Glycerin according to GOST 6259−75.
Coals spectral high purity-7−3, with a diameter of 6 mm.
Graphite electrodes with a diameter of 1.5−2 mm, length 15−20 mm, machined from a spectral coals.
Crucibles porcelain N 4.
The quartz glasses with a capacity of 50 cm.
Glasses chemical glass with a capacity of 50, 100, 300, 500 and 1000 cm.
Volumetric flasks with a capacity of 50, 100, 250 and 1000 cm.
Pipettes with a capacity of 1, 2, 5, 10 cm.
Nitric acid GOST 4461−77, H. h, distilled (second fraction) 5 mol/l, 0.5 mol/DM
, solutions of a mass fraction of 10% and 0.5%.
Hydrochloric acid by the GOST 3118−77, H. h
Hydrogen peroxide according to GOST 10929−76.
Ammonia water according to GOST 3760−79 diluted 1:1.
Phytin medical, solution with a concentration of 20 g/lin 0.5 mol/DM
nitric acid. Phytin, pre-cleaned in the following manner: the sample is dissolved in nitric acid solution with a mass fraction of 0.5% and the undissolved precipitate was filtered off. To the filtrate ammonia is added to pH 7.5. The separated precipitate is dissolved in nitric acid with a mass fraction of 10% and passed through activated carbon. Then repeat the operation of deposition of ammonia and the separated precipitate was dried in a drying Cabinet at a temperature of 80−85 °C.
Oxides of lanthanum and europium with a mass fraction of cerium dioxide of less than 5·10%. Oxides of neodymium and yttrium with a mass fraction of cerium dioxide of less than 1·10
%.
Cerium dioxide, CEO-L or more pure.
A standard solution of cerium (spare) with a concentration of 1 mg/cmin terms of cerium dioxide: a sample of cerium dioxide with a mass of 0.1 g dissolved in 5−7 cm
of concentrated nitric acid with the addition of 0.5−1.0 cm
of hydrogen peroxide, heated and boiled for 30−40 min. Then solution was cooled and transferred to volumetric flask with a capacity of 100 cm
, adjusted to the mark with water and mix.
Working solutions of cerium with the concentration of 0.01 and 0.001 mg/cmin terms of cerium dioxide prepared by successive dilution with water reserve solution. The solutions were prepared the day of use.
(Changed edition, Rev.
N 1, 2).
7.2. Preparation for assay
7.2.1. Impregnation of graphite electrodes
5−10 graphite electrodes placed in a porcelain crucible and kept in muffle furnace at 300 to 350 °C for 30 min. Vial 3, bent at an angle of 100−120°, secured to the tripod 4. In the vertical part of the load of 20−23 g of paraffin and immersed in the Cup 2 with glycerol, heated to 70 °C and can withstand up to melt the paraffin. In melted paraffin portions enter 7−9 g of polyethylene and again incubated at 70 °C until a homogeneous mass. In the inclined part of the tube is placed electrodes. The tube was stoppered, evacuated the air out of it and then drop the electrodes into the molten mass. The system is kept under vacuum for 6−8 h at a temperature of 100−110 °C. the Pump off, remove the test tube from the beaker and 2−3 min turn so that the holes in the socket and the tube coincide. While in the tube the air comes from the atmosphere. The electrodes removed, cleaned and placed 1−2 in the flame of a spirit lamp to remove excess amount of a mixture of polyethylene with paraffin. Then blade is cut by 0.2−0.3 mm from each end of the electrode. One of the ends of electrode wrap with plastic wrap and tightly inserted into a glass tube to a depth of 3−4 mm. the Electrode is immersed in the molten mass of a mixture of paraffin and polyethylene in a porcelain crucible, so that adjacent to the electrode end of the tube also immersed in the melt, and allowed to stand 5−10 C. Then removed and cooled to room temperature. The operation of immersion in the molten mixture, repeat 3−4 times. Cleaning the working surface of the graphite electrode with a razor blade, sand paper, and filter paper. The working surface of the electrode should be smooth and have a matte Shine. In the free end of the glass tube poured graphite powder for making contact with the device.
Before each determination, the electrode is subjected to mechanical cleaning and polishing on filter paper.
7.2,
7.2.2. Check graphite electrode
In a volumetric flask with a capacity of 25 cmis filled with 0.1 cm
of the working solution with a content of 0.01 mg/cm
of cerium oxide, 1.5 cm
5 mol/DM
nitric acid and 1 cm
of a solution of phytin and dilute to the mark with water. The solution was transferred into the electrolytic cell and immersed in it the graphite electrode prepared according to claim 7.2.1, and lead concentration at a potential of plus (1,2±0,05) with stirring for 10 min, Stop stirring and after 10−15 seconds register cathode voltammogram in the cathodic voltage scan at a speed of 20 mV/s. Potential fitata cerium (IV) is about -0.8 V. the Voltammogram of each solution is removed 3−4 times. The peak height is measured vertically, is drawn through the top of the peak to the intersection with a tangent connecting the bases of the branches peak. Each of the peak heights should not vary from the arithmetic mean value
by no more than 20%. If the height of the first peak differs from the average
by more than 20%, then the height of the first peak is not considered.
The electrode is considered suitable for use if the height of the peak on the voltammogram for a solution with a concentration of 0.05 mg/cmnot less than 40−50 mm in instrumental sensitivity of 0.04 µa/cm oscilloscope polarograph-5122−03 the height of the peak is not less than 70−80 mm, current range
, sweep rate 0.25 V/s, type of polarogram differential. With a smaller value of the electrode is subjected to repeated mechanical cleaning with sandpaper and polished on filter paper.
(Changed edition, Rev. N 1
, 2)
7.3. Analysis
7.3.1. A portion of the sample weighing 0.1−0.3 g were placed in a glass with a capacity of 50 cm, moistened with distilled water, add 2 cm
to 5 mol/DM
nitric acid and 1 cm
of hydrogen peroxide and leave until dissolved. In the analysis of yttrium and neodymium solution is heated to 40−60 °C. the solution was Then evaporated to dryness. The dry residue is dissolved in 1−2 cm
of distilled water, 1.5 cm
5 mol/DM
nitric acid and 1 cm
of a solution of phytin. The solution was quantitatively transferred to a volumetric flask with a capacity of 25 cm
, adjusted to the mark with water, transferred into the cell and remove the voltammogram according to claim
Simultaneously with the samples through all stages of the analysis carried out control experience in chemicals. The correction control experience should not be more than 0.05 mcg, otherwise change the reagents.
Mass fraction of cerium dioxide in the sample find for the calibration schedule.
(Changed edition, Rev. N 1,
2).
7.3.2. Construction of calibration curve
In glasses with a capacity of 50 cmplaced sample of the corresponding oxides (lanthanum, europium, neodymium or yttrium) with a mass of 0.1 g and injected 0; 0,1; 0,3; 0,6 and 1 cm
of the working solution of cerium dioxide with a concentration of 0.001 mg/cm
, which corresponds to 0; 0,0001; 0,0003; about 0.0006 and 0.001 mg of cerium dioxide. Dissolving lead according to claim
. Remove voltamperometry solutions according to claim 7.2.2 and build a calibration curve, causing the x-axis the mass of dioxide of cerium in mg per 25 cm
of the solution, and on the y-axis the corresponding value in mm of the heights of peaks of cerium dioxide.
7.4. Processing of the results
7.4.1. Mass fraction of cerium dioxide () in percent is calculated by the formula
where is the mass of dioxide of cerium was found in the calibration graphics mg;
— the weight of the portion of the sample,
All the high peaks to calculate the results of voltammetric determination of cerium count on one instrumental sensitivity.
The result of the analysis take the average of results of two parallel measurements.
7.4.2. Discrepancies in the results of two parallel determinations or the results of the two tests should not exceed the values of permissible differences given in table.3.
Table 3
| Mass fraction of cerium dioxide, % wt |
Allowable difference, % |
5·10 |
4·10 |
1·10 |
0,8·10 |
2·10 |
1,6·10 |
5·10 |
4,0·10 |
1·10 |
0,6·10 |
3·10 |
1·10 |
7.3.2−7.4.2. (Added, Rev. N 1).
8. DEFINITION OF EUROPIUM
The method is based on the polarographic determination of europium in the alkaline solution of Trilon B and chloride of sodium.
Permissible mass fraction of lead may exceed the mass fraction of EU (europium oxide) is not more than 10 times.
8.1. Apparatus, reagents and solutions
Polarograph PPT-1 or similar with mercury dripping electrode is a cathode and bottom mercury anode.
Tile electric.
The chemical glasses with a capacity of 50 and 2000 cmaccording to GOST 1770−74.
Argon gas GOST 10157−79.
Reducer oxygen.
Pressure gauge according to GOST 2405−88.
Mercury metal according to GOST 4658−73 brand R-1.
Pyrogallol And a solution with a concentration of 0.25 g/cmin a solution of potassium hydroxide with a concentration of 0.25 g/cm
.
Potassium hydroxide according to GOST 24363−80, H. h, solution with concentration of 2 mol/DM.
Trilon B according to GOST 10652−73, h.d. a.
Sodium chloride according to GOST 4233−77, H. h
Hydrochloric acid by the GOST 3118−77, H. h., diluted 1:1.
Rectified ethyl alcohol GOST 18300−87.
Phenolphthalein solution with a mass concentration of 10 g/DM.
Background polarographic, Trilon B solution (100 g/DM) in 15% strength sodium chloride solution with pH equal to 9: Trilon B sample weighing 200 g and of sodium chloride with a mass of 300 g is placed in a beaker with a capacity of 2 DM
, 1.5 DM flow
of water and 1−2 cm
of a solution of phenolphthalein is dissolved by heating to 60−80 °C, cooled to room temperature, neutralized with a solution of potassium hydroxide to a pink color, pour water to a volume of 2 DM
, thoroughly mixed.
Europium oxide brand Evo-1.
Gadolinium oxide brand of GDO-1.
A solution of europium (spare) containing 0.1 mg/cmeuropium (calculated as oxide): 100 mg of europium oxide were placed in a glass with a capacity of 50 cm
, moistened with water, pour 1−2 cm
of hydrochloric acid, heated on a hot plate until dissolved, cooled to room temperature, transferred to a volumetric flask with a capacity of 1 DM
, adjusted to the mark with water, mix.
The working solution of europium with concentration of 0.01 mg/cmoxide europium is prepared by diluting a backup solution polarographic background 10 times.
Solutions comparison, containing 0,02; 0,04; 0,08 and 0,16 mg of europium oxide is prepared as follows: four sample of gadolinium oxide with a mass of 200 mg was placed in four glasses, moisten with water, pour 2−3 cmof hydrochloric acid, dissolve while heating on a hot plate, pour 2, 4, 8 and 16 cm
working solution of europium, is evaporated to wet salts; pour 9 cm
polarographic background, neutralized with a solution of potassium hydroxide to obtain a pink color on phenolphthalein, is transferred in four flasks with a capacity of 50 cm
, bring to mark the background and
mix.
8.2. Analysis
Sample analyzed two samples weighing 200 mg were placed into cups with a capacity of 50 cm, moistened with water, pour 2−3 cm
of hydrochloric acid, heated on a hot plate to dissolve the sample is evaporated to wet salts, pour 10−15 cm
polarographic background. The solutions were cooled to room temperature, transferred to volumetric flasks with a capacity of 50 cm
, neutralized with a solution of potassium hydroxide to a pink color on phenolphthalein, bring the background up to the mark and mix. Through the solutions for 5 min flow of argon at a speed of two bubbles per second, then the solutions polarography in the range from minus 0.8 to minus of 1.3 V. the Potential peak of the europium of about minus 1.1 V.
Polarographic solutions of the sample and one of the solutions of the comparison, is selected so that the peak height of the solution comparison different from the peak height of the sample is not more than 1.5 times.
Simultaneously with the sample hold control experience in the chemicals through all stages of the analysis. The value of the peak on the voltammetric curve of the solution in the reference experiment is subtracted from the height values of the peak on the voltammetric curve of a solution of the sample.
8.3. Processing of the results
Mass fraction of oxide of europium () in percent is calculated by the formula
where ,
,
— the height of the peak in the current-voltage curves, respectively, for solutions of the samples in the reference experiment, solution, comparison, mm;
— weight of europium oxide in a solution of comparison, mg;
— weight of sample, mg.
The result of the analysis taking the arithmetic mean of the results of two parallel measurements. Discrepancies in the results of two parallel definitions and results of the two tests should not exceed the values of permissible differences given in table.4.
Table 4
| Mass fraction of oxides of europium, % |
Allowable difference, % |
| 0,01 |
0,002 |
| 0,02 |
0,004 |
| 0,05 |
0,01 |
| 0,10 |
0,02 |
Sec. 8. (Added, Rev. N 2).
