GOST 27973.1-88

• gost-279731-88.pdf (327.18 KiB)
  ГОСТ 27973.1-88

GOST 27973.1−88 Gold. Methods of atomic emission analysis (with Change No. 1)

GOST 27973.1−88

Group B59

INTERSTATE STANDARD

GOLD

Methods of atomic-emission analysis

Gold. Methods of atomic-emission analysis

AXTU 1709

Date of introduction 1990−07−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED the Main Directorate of precious metals and diamonds at the Council of Ministers of the USSR

DEVELOPERS

V. A. Dmitriev, candidate. tech. Sciences; V. P. Tomaszewski (leader); N. D. Sergienko, I. B. Kurbatov; T. A. Babayants; T. A. Kislitsina

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from 21.12.88 N 4375

The change in N 1 taken by the Interstate Council for standardization, Metrology and certification (minutes N 11 dated 25.04.97)

Was the Technical Secretariat of MGS N 2519

The adoption of the changes voted:

3. REPLACE GOST 13611.1−79

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)

6. REVISED (June 1999) Change 1, approved in September 1997 (IUS 12−97)


This standard specifies the methods of atomic-emission determination of impurities, silver, copper, iron, platinum, palladium, rhodium, bismuth, lead, antimony, zinc, manganese, Nickel, chromium, tin, arsenic, silicon, magnesium, cadmium, aluminum and tellurium in gold with a mass fraction of gold is not less than 99.9%.

(Changed edition, Rev. N 1).

1. ATOMIC-EMISSION METHOD FOR THE DETERMINATION OF IMPURITIES
IN SAMPLES OF ARBITRARY SHAPE

The method is based on the evaporation and excitation of the atoms of the sample of globules (liquid drops of the melt) in the arc discharge, the photographic registration of the spectrum and then measure the intensity of spectral lines of the identified elements. The relationship of the intensity of lines with the contents of the element in the sample set with the help of calibration curve by standard samples.

The method allows to determine the mass fraction of impurities in the intervals given in table.1.

Table 1

The error analysis results the determined values of mass fractions of impurities with the confidence coefficient =0.95 is given in table.2.

Table 2

(Changed edition, Rev. N 1).

1.1. General requirements

General requirements for method of analysis according to GOST 27973.0.

1.2. Apparatus, reagents and materials

The quartz spectrograph medium dispersion spectrograph or diffraction large dispersion.

Arc generator of alternating current.

Microphotometer.

Reliever quartz three-stage.

Electric stove with a closed spiral.

Spectrographic plates of types 1, 2, 3, ES, or other contrasting materials.

Electrode holders with forced cooling.

Electrodes, carbon, spectral-pure helium high purity-7 — 3:

— diameter of 6−10 mm and a length of 30−50 mm with a conical recess 1 mm;

— diameter of 6−10 mm and length 30−50 mm, sharpened to a truncated cone or hemisphere.

A pair of tweezers.

Grinding machine carbon electrodes.

Analytical scales of the 2nd class.

The mold is steel with an inner diameter of the matrix of 3−5 mm.

Crucibles porcelain with GOST 9147.

Contrast developer and fixer for photographic plates.

The technical rectified ethyl alcohol according to GOST 18300.

Hydrochloric acid of high purity according to GOST 14261, diluted 1:1.

Standard samples of gold.

(Changed edition, Rev. N 1).

1.3. Preparation for assay

Samples are taken from four sample weighing 200 mg each, from each standard sample or two. The gold surface is cleaned in accordance with GOST 27973.0.

Before starting work on the spectrograph, you must:

— check the correct installation of the three-stage attenuator, the width of the gap;

— clean the electrode holders alcohol from the surface of the dirt;

— turn on water-cooling the electrode holders;

— check the operation of the locking and grounding the tripod and generator.

1.4. Analysis

Prepared for analysis a portion of sample or standard sample is placed in the recess of the lower carbon electrode. The counter serves as a carbon rod, sharpened to a truncated cone or hemisphere.

Spectra photographed with the spectrograph being system of the slit illumination via the three-step attenuator.

The width of the slit of a spectrograph of 0.015−0.020 mm; exposure time — 30 to 60 C.

The interelectrode gap is set at the magnified image of the arc on the screen the intermediate aperture with a height of 5 mm and maintain strictly constant, adjusting it throughout the exposure.

As a source of spectra excitation is used in arc AC current And 3−5, the phase of firing of 60°.

When determining the content of silver and copper more than 0.003% of the photography of the spectra of the samples is carried out again on the photographs lower sensitivity. For each standard sample receive two, and for each sample of four spectrograms. Photographic plates showing, rinsed in water, fixed, washed in running water and dried.

The wavelengths of the analytical lines is recommended to perform the analysis, are given in table.3.

Values pucherani background used as lines of comparison should be in the region of normal pochernenija.

Table 3

(Changed edition, Rev. N 1).

1.5. Processing of the results

Determination of impurities is carried out by the method of «three standards». On each spectrogram to measure the blackening of analytical lines of the designated element (see table.3) and nearby background (minimum blackening near the analytical line of the element on either side, but with the same in all spectra on the same photographic plate) or comparison lines . Calculate the difference of pochernenija or . The values of and obtained two spectrograms for each standard sample, find the arithmetic mean .

Calibration curve constructed in the coordinates: the average value of the difference pucherani () line of the element and the background is the logarithm of the mass fraction of the element in the standard sample. According to the results of photometry of spectrograms of the samples have the value and calibration schedule find the mass percent of impurities in the analyzed sample of gold.

The result of the analysis taking the arithmetic mean of results of four parallel measurements obtained on the same photoplate

nke.

1.6. Control of accuracy of analysis results

1.6.1. Under the control of the convergence and divergence of reproducibility of results of parallel measurements (the difference between the largest and smallest of the four definitions) and the results of two tests with a confidence level =0.95 does not exceed the values of permissible differences given in table.4.

Table 4

For intermediate values of the mass fraction of permissible differences calculated using linear interpolation.

1.6.2. Control of accuracy of analysis results is carried out according to GOST 27973.0.

2. ATOMIC-EMISSION METHOD FOR THE DETERMINATION OF IMPURITIES IN THE SAMPLES MADE IN THE FORM OF RODS

The method is based on the evaporation and excitation of the atoms of the sample in an electric arc or spark discharge, the photographic registration of the spectrum and then measure the intensity of spectral lines of the identified elements. The relationship of the intensity of lines with the contents of the element are set with the help of calibration curve by standard samples.

The method allows to determine the content of impurities in the intervals given in table.5.

Table 5

The error analysis results the determined values of mass fractions of impurities with the confidence coefficient =0.95 is given in table.6.

Table 6

(Changed edition, Rev. N 1).

2.1. General requirements

General requirements for method of analysis according to GOST 27973.0.

2.2. Apparatus, materials and reagents

The quartz spectrograph medium dispersion spectrograph or diffraction.

Generator universal providing spark discharge and arc discharge of alternating current.

Tripod with forced cooling.

Electric stove with a closed spiral.

Spectrographic plates of types 1, 2, 3, ES, or other contrasting materials.

Microphotometer.

Files velvet.

Crucibles porcelain with GOST 9147.

Hydrochloric acid of high purity according to GOST 14261, diluted 1:1.

Contrast developer and fixer for photographic plates.

Standard samples of composition of gold in the form of cast rods.

(Changed edition, Rev. N 1).

2.3 Preparation for assay

Come to the analysis of samples in the form of two cast rods with a diameter of 6−8 mm, length 20−70 mm. the ends of the rods are sharpened to a hemisphere, is treated with a velvet rasp to obtain a smooth surface, after which the gold surface is cleaned in accordance with GOST 27973.1.

2.4. Analysis

Samples prepared in accordance with paragraph 2.3, are the upper and lower electrodes when photographing spectra.

Spectra photographed at slit width of the spectrograph 0,015 mm When lighting cracks through single-lens condenser the distance between the electrodes 1.5−2.0 mm set the pattern. When lighting cracks through being a capacitor, the height of the intermediate diaphragm 5 mm; exposure for 30−60 s.

Wavelength of analytical spectral lines is recommended to perform the analysis are given in table. 7.

When determining the mass fraction of silver and copper more than 0,002% for the excitation spectra of the applied spark discharge, an electric charge current of the capacitor of 2.0−2.5 And the time of sparking 15 s

When determining the mass fraction of silver and copper less than 0.004% and the mass fraction of iron, platinum, palladium, rhodium, bismuth, lead, antimony, zinc, manganese, Nickel, chromium and tin for the excitation spectrum is used, the arc discharge of alternating current a current of 5−6 And a baking time of 15 s.

In the same conditions photographed spectra of standard samples of composition of gold.

For each of the sample receive four spectrograms for each standard sample — two.

Exposed a photographic plate showing, then rinsed with water, fixed, washed in running water and dried.

2.5. Processing of the results

On each spectrogram, measure the blackening of analytical lines of the designated element (see table.7) and the nearby background (minimum blackening near the analytical line of the element on either side, but with the same in all spectra on the same photographic plate) or a line item comparison .

Table 7

Calculate the difference of pochernenija or .

The values of and obtained two spectrograms for each standard sample, find the arithmetic mean .

The values for standard samples and analyzed samples are transferred to corresponding values of the logarithms of relative intensity using the app to GOST 13637.1.

Calibration curve constructed in the coordinates: logarithm of relative intensity (or if you use element comparisons) and the logarithm of the mass fraction of the element in the standard sample.

With the help of calibration chart, find the mass percent of the element in the sample.

The result of the analysis taking the arithmetic mean of results of four parallel measurements.

(Changed edition, Rev. N

1).

2.6. Control of accuracy of analysis results

2.6.1. Under the control of the convergence and divergence of reproducibility of results of parallel measurements (the difference between the largest and smallest of the four definitions) and the results of two tests with a confidence level =0.95 does not exceed the values of permissible differences , is given in table.8.

Table 8

For intermediate values of the mass fraction of permissible differences calculated using linear interpolation.

2.6.2. Control of accuracy of analysis results is carried out according to GOST 27973.0.