GOST 20997.1-81
BL 6−99
GOST 20997.1−81
INTERSTATE STANDARD
THALLIUM
METHOD OF SPECTRAL DETERMINATION OF MERCURY
Edition official
IPK PUBLISHING house of STANDARDS, Moscow
INTERSTATE STANDARD
THALLIUM
Method of spectral determination of mercury
Thallium.
Method of spectral determination of mercury
GOST
20997.1−81* *
Instead
GOST 20997.1−75
AXTU 1709
The decision of the State Committee USSR on standards on 25 may 1981 No. 2589 the introduction of set
with 01.07.82
Resolution of the state standard from
This standard specifies the method of spectral determination of mercury in thallium with mass fraction of mercury from 110−5 to 110 3%.
Determination of the mass fraction of mercury in thallium is performed according to the method of «three standards» with the evaporation of mercury from the crater of the graphite electrode arc AC.
(Changed edition, Rev. No. 2).
1. GENERAL REQUIREMENTS
General requirements for method of analysis according to GOST 20997.0−81.
2. APPARATUS, REAGENTS AND MATERIALS
The quartz spectrograph medium dispersion of any type with being system of the slit illumination or the spectrograph type STE-1.
Arc generator of alternating current.
Spectromancer of PS-18.
Microphotometer of any type, allowing to measure the density of the blackening of analytical lines.
The damping of the three — and nine -.
Libra torsion bar type W or similar with a weighing error of no more than 0.001 g analytical Scale with a weighing error of no more than 0,0002 g.
Electrodes of graphite brand S-2, S-3 6 mm in diameter with a crater size 4 x 10 mm Contractrate coal of 6 mm in diameter, sharpened to a truncated cone with ground diameter of 2 mm.
Photographic plates «spectrographic» type II.
Mercury metal according to GOST 4658−73.
Thallium metal with a mercury content of less than 1 • 106 %.
Sodium hydroxide according to GOST 4328−77, H. h
Samples comparison.
Nickel crucibles.
Official edition Reprinting is prohibited
* Edition (January 2001) with Amendments No. 1, 2 approved in November 1986 April 1992
(ICS 2−87, 7−92)
© Standards publishing house, 1981 © IPK Publishing house of standards, 2001
p note. Allowed the use of devices with photoelectric registration of spectrum and other spectrographic devices and systems, other reagents and materials subject to receipt of the accuracy characteristics as specified in this standard.
Section 2. (Changed edition, Rev. No. 2).
3. PREPARATION FOR ASSAY
The basis for the preparation of samples for constructing the calibration curve thallium is a metal with a mass fraction of mercury less than 110 6%. Prepare the parent sample with a mass fraction of mercury of 0.1% in pre-weighed on an analytical balance glass capillary with an inner diameter of 0.1 mm gain calculated weight of mercury and blow it on the record metal thallium. In the Nickel crucible is placed a small amount of sodium hydroxide; melt at a temperature of 320−340 °C and the resulting melt down of the prepared sample of mercury (10 mg) and thallium (10 g). The melt was thoroughly stirred, poured into a porcelain Cup, cooled and placed in running water to dissolve the alkali. The resulting alloy of thallium and mercury is transferred to a glass buxu and stored under a layer of distilled water to prevent oxidation of thallium. The head sample is carefully analyzed by a colorimetric method. Method serial dilutions of a primary sample and each re-fused based get series of working samples comparison with a mass fraction of mercury in percent: 110 5; 210−5; 610−5; 1,2−10−4; 410−4; MO-3.
References must be certified in accordance with normative-technical documentation. Samples stored in buksh under a layer of distilled water. Shelf life 1 year
Section 3. (Changed edition, Rev. No. 1, 2).
4. PROVIDENIE ANALYSIS
Mercury determination is carried out on the quartz spectrograph medium dispersion or STE-1 being the illumination system of the slit. The width of the slit of a spectrograph 0,020 mm. the Weight of the portion of the sample or the reference sample (250 mg) in the form of metal filings placed in the crater of the graphite electrode with a depth of 10 mm and a diameter of 4 mm and compacted with a kick ball made of organic glass. Between vertically placed electrodes ignite the arc of an alternating current power 15 A. exposure Time 20 s, the distance between the electrodes of 2.5−3.0 mm.
Spectra of the samples and comparison samples are photographed three times on the same photographic plate using a three-step attenuator. To construct the characteristic curve of photographic plates using a nine-reliever photographed the spectrum of iron.
5. PROCESSING OF THE RESULTS
5.1. In the spectrogram, using microphotometry measure the blackening of analytical lines of mercury Hg I 253,652 nm and the surrounding background (right of the line). On the measured values, using the characteristic curve, determine the logarithms of the intensity of the lines and background lg (7L + /f) and the logarithm of the background intensity lg/f. Then /l = (/l + /f) — /f. The calibration graphs built by laying on the ordinate the values of the logarithm of the intensity of the mercury line (lg/j) on the x — axis is the logarithm of the mass fraction of mercury (lgQ. For the calibration chart to find the mass percent of mercury in thallium. It is allowed to use tables, given in GOST 13637.1−93.
5.2. Discrepancies in the results of two parallel definitions (d), as well as discrepancies in the results of the two analyses (D) shall not exceed the values given in the table (R = 0,95).
| Mass fraction of mercury, % | The discrepancy between the results of two parallel definitions % | The discrepancy between the results of two tests, % |
| 1 10"5 | 310"6 | 4−10 6 |
| 2−10 5 | 6 10"6 | 7 • 10 6 |
| 4−10 5 | MO-5 | 2 10"5 |
| 8−10 5 | 2−10 5 | 3 10"5 |
| MO-4 | 3 10"5 | 410−5 |
| 2−10 4 | 6 10"5 | 710−5 |
| 4−10 4 | MO-4 | 2 10"4 |
| 8−10 4 | 2 10"4 | EVIL 4 |
| 1 10"3 | 3 10"4 | 4−10 4 |
Permitted discrepancies for the intermediate mass fraction calculated using linear interpolation or according to the formulas
d = 0.28 x; D = 0,36,
where x is the arithmetic mean of the results of parallel measurements;
— the arithmetic mean of the results of the two tests.
(Changed edition, Rev. No. 2).
Editor of M. I. Maksimova Technical editor N. With. Grishanova Corrector Kabasawa M. S. desktop publishing C. V. Ryabova
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