GOST 27973.3-88

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  ГОСТ 27973.3-88

GOST 27973.3−88 Gold. Method of atomic-absorption analysis

GOST 27973.3−88

Group B59

INTERSTATE STANDARD

GOLD

Method of atomic-absorption analysis

Gold. Method of atomic-absorption 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. D. Small, PhD. Fiz.-Mat. Sciences (chair); T. D. Gornostaeva, PhD. chem. Sciences; G. E. Jerkovic, PhD. Fiz.-Mat. Sciences; M. V. Usol’tseva, O. A. Menshikova; T. P. Gray

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

3. REPLACE GOST 13611.2−79

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. REPRINTING. June 1999


This standard establishes the atomic absorption method for determination of impurities, silver, copper, iron, platinum, palladium, rhodium, bismuth, lead, antimony, zinc, manganese, Nickel, and chromium in gold with a mass fraction of gold is not less than 99.9%.

The method is based on the evaporation and atomization of the sample solution into the flame of a gas burner or heated graphite furnace and measurement of the atomic absorption resonance lines of the determined elements. The relationship of size of absorption with the concentration of the element in the solution set with the help of calibration curve.

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 probability =0.95 is given in table.2.

Table 2

1. GENERAL REQUIREMENTS

General requirements for method of analysis according to GOST 27973.0.

2. APPARATUS, MATERIALS AND REAGENTS

Spectrophotometer, atomic absorption, allowing to work with flames of propane-butane-air and acetylene-air, and the heated graphite furnace.

The spectral lamp with a hollow cathode for the determination of silver, rhodium, palladium, platinum, lead, bismuth, zinc, copper, Nickel, chromium, manganese, iron, and antimony.

Analytical scales of the 2nd class.

Electric stove with a closed spiral.

Muffle furnace with thermostatic control.

Propane-butane in cylinders for technical GOST 20448.

Acetylene, dissolved and gaseous technical GOST 5457.

Argon gas according to GOST 10157.

Standard samples of gold.

The agate mortar.

Pipettes with a capacity of 1, 5, 10 cm,with divisions for NTD.

Volumetric flasks with a capacity of 25, 50, 100, 1000 cmaccording to GOST 1770.

Cylinder measuring capacity 10 cmand beakers capacity 50, 100, 250, 1000 cmaccording to GOST 1770.

Glasses glass with a capacity of 50, 100, 200 cmaccording to GOST 25336.

Funnels, glass, or quartz pitch with a capacity of 100 and 500 cmaccording to GOST 25336.

The corundum crucibles.

Obestochennye the filter paper of «blue ribbon» «white ribbon».

Hydrochloric acid of high purity according to GOST 14261 and diluted 1:1, 1:5.

Nitric acid of high purity according to GOST 11125 and diluted 1:1.

Sulfuric acid of high purity according to GOST 14262 and diluted 1:9.

Toluene according to GOST 5789.

Dibutilsul.

Dimetilsulfoxid solution in toluene with a molar concentration of 1.0 mol/DMis prepared as follows: 175 seedimetilsulfoxid placed in a separating funnel with a capacity of 500 cm, 100 cm pouredhydrochloric acid solution (1:5) and shaken for 3 min. After separation the aqueous phase is poured in the separating funnel again, pour the 100 cmof hydrochloric acid and an operation of washing dimetilsulfoxid repeat. After separation of the phases, dibutilsul transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with toluene and mixed.

Dimetilsulfoxid solution in toluene with a molar concentration of 0.5 mol/lis prepared by dilution of a solution (1.0 mol/DM) toluene in a ratio of 1:1.

Tartaric acid according to GOST 5817, a solution of 10 g/DM.

Cadmium sulfate according to GOST 4456.

Buffer solution of cadmium sulfate containing 5 mg/cmof cadmium, prepared as follows: a portion of sulphate of cadmium with a mass of 11.4 g was placed in a volumetric flask with a capacity of 1000 cm, 500 cm, addwater, mix to dissolve the salt, bring to the mark with water and mix.

Barium peroxide according to normative-technical documentation.

Gold of high purity with a mass fraction of gold is not less than 99.999%.

Silver GOST 6836*.
_______________
* On the territory of the Russian Federation GOST 6836−2002. — Note the manufacturer’s database.

Carbonyl iron, radio GOST 13610.

Copper according to GOST 859*.
_______________
* On the territory of the Russian Federation GOST 859−2001. — Note the manufacturer’s database.

Bismuth GOST 10928.

Lead of high purity according to GOST 22861.

Zinc GOST 3640.

Antimony GOST 1089.

Manganese metal according to GOST 6008.

Nickel GOST 849.

Chrome metal according to GOST 5905*.
_______________
* On the territory of the Russian Federation GOST 5905−2004. — Note the manufacturer’s database.

Palladium powder according to GOST 14836*.
_______________
* On the territory of the Russian Federation from 01.01.2008 standards 31291−2005. — Note the manufacturer’s database.

Platinum powder according to GOST 14837*.
_______________
* On the territory of the Russian Federation from 01.01.2008 standards 31290−2005. — Note the manufacturer’s database.

Rhodium powder according to GOST 12342 or rhodium trichloride th

tiredly.

2.1 Preparing the standard solutions

Standard solutions containing 2 mg/cmof bismuth, iron, copper and Nickel: a portion of each of these metals with a mass of 200 mg was dissolved in 10 cmof nitric acid (1:1) under heating. The solution is evaporated to a volume of 2−3 cm, add 20 cmof a hydrochloric acid solution (1:5), transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with the same acid solution and stirred.

A standard solution containing 2 mg/cmlead: charge lead with a mass of 200 mg was dissolved in 10 cmof nitric acid (1:1) under heating. The solution was transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix.

A standard solution containing 1 mg/cmof silver: a suspension of metallic silver weighing 100 mg was dissolved in 10 cmof nitric acid (1:1) under heating, then add 50 cmof hydrochloric acid and boil to complete dissolution of the precipitate of silver chloride. The solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with hydrochloric acid (1:1) and stirred.

A standard solution containing 2 mg/cmof antimony: a portion of metallic antimony with a mass of 200 mg was dissolved in 20 cmof a mixture of hydrochloric and nitric acids (3:1) under heating. The solution is evaporated to a volume of 2−3 cm, add 20 cmof a hydrochloric acid solution (1:5), transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with the same acid solution and stirred.

Standard solutions containing 2 mg/cmchromium, zinc, and manganese: a portion of each of these metals with a mass of 200 mg was dissolved in 10 cmof hydrochloric acid (1:1) under heating. The solutions were transferred to volumetric flasks with a capacity of 100 cm, adjusted to the mark with hydrochloric acid (1:5) and stirred.

A standard solution containing 2 mg/cmof platinum: a sample of platinum weighing 200 mg are dissolved in 20 cmof a mixture of hydrochloric and nitric acids (3:1) under heating, the solution is evaporated to a volume of 3−5 cm, flow 20 cmof a hydrochloric acid solution (1:5), transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with the same acid solution and stirred.

A standard solution containing 2 mg/cmof palladium: palladium sample mass of 200 mg dissolved in 20 cmof nitric acid by heating, the solution is evaporated to a volume of 3−5 cm, flow 20 cmof a hydrochloric acid solution (1:5), transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with the same acid solution and stirred.

A standard solution containing 2 mg/cmof rhodium, prepare one of the following ways.

A portion of rhodium (in powder) mass of 200 mg was mixed thoroughly with 5-fold quantity of peroxide of barium, fray in an agate mortar, transferred to a corundum crucible and sintered in air for 2−3 hours at a temperature of 800−900 °C (the crucible is put in a cold muffle). Sintered is cooled, transferred to a beaker with a capacity of 200 cm, moistened with water and dissolved in a solution of hydrochloric acid (1:1) until complete dissolution. If, after the dissolution of SPECA in hydrochloric acid is a residue, sintering and dissolution repeat. The resulting solution is diluted with water to a volume of 50 cmand precipitated barium sulfate by adding sulfuric acid solution (1:9) portions with constant stirring. The solution is heated to a temperature of 60−70 °C. after 2−3 hours check the completeness of the precipitation of the barium sulfate and filter it through filter «blue ribbon», or double filter «white ribbon» in a volumetric flask with a capacity of 100 cm. The filter cake was washed 4−5 times with hot hydrochloric acid (1:5), and then 5−6 times with hot water. The solution was adjusted to the mark with hydrochloric acid (1:5) and stirred.

A suspension of rhodium trichloride ground 546,7 mg dissolved in 20 cmof a hydrochloric acid solution (1:1) at weak heating, the solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with hydrochloric

acid (1:5) and stirred.

2.2. Preparation of standard solutions containing an amount of the determined elements

Solution a: in a volumetric flask with a capacity of 100 cmis placed 5 cmcore standard solutions of bismuth, iron, copper, Nickel, lead, manganese, antimony, chromium, zinc, platinum, palladium, rhodium and 10 cmprimary standard solution of silver, adjusted to the mark with hydrochloric acid (1:5) and stirred.

1 cmof the solution contains 100 µg of each of the identified elements.

Solution B: in a volumetric flask with a capacity of 100 cmis placed 10 cmsolution A, was adjusted to the mark with hydrochloric acid (1:5) and stirred.

1 cmof the solution contains 10 µg each of the identified elements.

3. PREPARATION FOR ASSAY

3.1. Preparation of samples for analysis

3.1.1. To perform the analysis selected for two whole gold weight of 0.2−5.0 g (table.3), each of which is placed in a beaker with a capacity of 50−100 cmand purify the gold surface according to GOST 27973.0.

The sample was dissolved with mild heating in 10−30 cmof a freshly prepared mixture of hydrochloric and nitric acids (3:1), adding it in batches of 5−7 cm. After complete dissolution of gold, the solution is evaporated to a volume of 3−5 cm, remove from heat and add 5−10 cmof hydrochloric acid solution (1:5). The solution was cooled and quantitatively transferred to a volumetric flask with a capacity of 25 cm, adjusted to the mark with hydrochloric acid (1:5) and stirred. If the number of the designated impurities is not more than five, and the mass fraction of each of them exceeds 0.004%, the dilution may be performed to a volume of 10 cmin a graduated cylinder with a capacity of 10 cm. For the determination of palladium and iron taken 5 cmof the prepared sample solution was placed in a flask with a capacity of 25 cmand used for analysis.

Table 3

3.1.2. The remainder of the solution transferred to a dry separatory funnel, add 10−30 cm(depending on the mass of the sample) solution of dibutylaniline in toluene (1.0 mol/DM) and extracted gold for 3 min. After separation the aqueous phase is drained into another separating funnel, add 10−20 cmof a solution of dibutylaniline in toluene (0.5 mol/DM) and re-extracted gold for 3 min. When the charge weight of 5.0 g of gold extraction is carried out three times. To do this, after the second extraction the aqueous phase is poured into a dry separatory funnel, add 10 cmof a solution of dibutylaniline in toluene (0.5 mol/DM) and extracted gold for 3 min.

After separation the aqueous phase is decanted into a dry flask with a capacity of 25 cm. The resulting solution was supplied for analysis.

Recovery of gold from the organic phase is carried out according to the method given in the Appendix.

For gold separation allowed the use of other extractants, is not inferior to dibutylaniline in extraction ability in relation to gold, subject to receipt of the metrological characteristics of the technique are not worse than specified in this standard

.

3.1.3. The definition of the contents of silver and copper more than 0.02% may be performed without separation of gold. For the preparation of samples for analysis carry out according to claim 3.1.1.

3.2. Preparation of solutions comparison

3.2.1. For the determination of impurities in solution without separation of gold using solutions comparison, containing all the trace elements and gold.

Solution containing 50 mg/cmof gold is prepared by dissolving the weighed portion of high purity gold weight of 5.0 g p.3.1.1. The solution of gold is transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with hydrochloric acid (1:5) and stirred.

Solutions comparison with the mass concentration of the determined elements 0,5, 1,0, 1,5, 2,0, 5,0 µg/cmand gold 20 mg/cmis prepared as follows: in a volumetric flask with a capacity of 50 cmis placed aliquote parts of solutions A or B (tab.4), one adds 20 cmof a solution containing 50 mg/cmof gold, adjusted to the mark with hydrochloric acid (1:5) and stirred.

Table 4

In flasks with a capacity of 25 cmtaken at 10−20 cmof the solutions prepared comparison and is used for determination of palladium, iron, copper and silver.

3.2.2. For determining chromium, antimony, platinum and bismuth on the atomization of samples in a graphite furnace using solutions comparison, prepared according to claim 3.2.1 with subsequent extraction of gold solution in toluene dimetilsulfoxid according to claim 3.1.2.

With this purpose, the remaining volume of the solution transferred to a dry separatory funnel and extracted gold solution dibutylaniline in toluene in two stages. After extraction of the gold aqueous phase is poured into flasks with a capacity of 25 cm.

Solutions comparison with the mass concentration of the determined elements 0,25, 0,50, 0,75 and 1.00 µg/cmis prepared by diluting two times the solutions obtained after extraction of the gold. In flasks with a capacity of 25 cmis placed 5 cmof each solution (TCA-1 — TCA-4), add 5 cmof a solution of tartaric acid in the determination of antimony, or 5 cmof hydrochloric acid solution (1:5) in the determination of platinum, chromium, bismuth, and mix.

3.2.3. For the determination of silver, lead, antimony, bismuth, zinc, copper, Nickel, manganese, chromium, rhodium and platinum in the atomization of the sample in the flame use solutions comparison, prepared from the standard solutions A and B without the addition of gold.

Solutions comparison with the mass concentration of the determined elements 0,2, 0,5, 1,0, 2,0 and 5,0 ág/cmis prepared as follows: in a volumetric flask with a capacity of 50 cmis placed aliquote parts of solutions A or B (tab.5), adjusted to the mark with hydrochloric acid (1:5) and stirred.

Table 5

4. ANALYSIS

4.1.Analysis with atomization of the sample in the flame

Atomic absorption spectrometer is ready to work and include according to the instruction manual of the device. Measure the atomic absorption of the elements is carried out by analytical spectral lines with wavelengths given in table.6.

Table 6

Methods of preparation of samples for analysis, and flames used to define the various elements are given in table.7.

Table 7

_______________
* In a flask with a capacity of 25 cmtaken 5 cmof the analyzed solution samples, or solution comparison, add 5 cmof cadmium sulfate solution and stirred.


Solutions and comparison solutions of samples analysed successively sprayed into the flame of a gas burner and measure the atomic absorption of the element. For each element perform at least two measurements and calculate the average value of absorption.

Calibration curve constructed in the coordinates: the value of absorption (the average of measured values) — mass concentration of the element in the solution comparison.

The average value of absorption using the calibration curve find the concentration of element () to the solution of the sample.

4.2. Analysis with atomization of the sample in the graphite furnace (HCA)

Determination of bismuth, chromium, antimony and platinum for the mass concentration of less than 0.005% is carried out with a sample atomization in graphite furnace. The conditions of atomization in a furnace HCA-74 are given in table.8.

Table 8

At the stage of atomization using the «gas-stop» or «minimal flow of inert gas».

Solutions and comparison solutions of samples analysed successively introduced into the graphite furnace, include a programming device and a heated oven for a given program (see table.8). Account nonselective absorption carried out using a deuterium background corrector.

In the determination of antimony in all analyzed solutions was added to a solution of tartaric acid. To this end, in a flask with a capacity of 25 cm,take 2 cmof the sample solution, add 2cmof a solution of tartaric acid and stir. For dilution of the analyzed solutions in the determination of antimony in a solution of tartaric acid, and in the determination of bismuth, chromium and platinum — hydrochloric acid solution (1:5).

The measurement of the absorption and construction of calibration curve carried out in accordance with clause 3.1.

5. PROCESSING OF THE RESULTS

Mass fraction of the element-impurities () in percent is calculated by the formula

,

where is the mass concentration of the element was found in the calibration schedule, µg/cm;

 — the volume of the main solution of the sample, cm;

 — the coefficient corresponding to the degree of dilution of the basic solution;

 — the weight of the portion,

The result of the analysis taking the arithmetic average of the results of two parallel measurements.

6. CONTROL OF ACCURACY OF ANALYSIS RESULTS

6.1. Under the control of the convergence and divergence of reproducibility of results of parallel measurements and the results of the two analyses (the difference between larger and smaller) with the confidence coefficient =0.95 does not exceed the values of permissible differences given in table.9.

Table 9

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

6.2. The accuracy of the results of the analysis according to GOST 27973.0.

APP (mandatory). METHOD OF RECOVERY GOLD FROM SOLUTION IN TOLUENE DIMETILSULFOXID

APP
Mandatory

The organic phase obtained after extraction of gold with a solution of dibutylaniline in toluene was placed in a beaker with a capacity of 1000 cmand evaporate on the stove at a moderate heat to moist salts.

Glass with gold and traces of organic substances removed from the plate, cool, add 5−10 cmof sulfuric acid and 15−20 cmof nitric acid. After passing the rapid oxidation of organic substances the glass of solution is placed on the stove and evaporated the solution to separation of vapours of sulphuric anhydride, and then the glass with the gold cooled, rinse the wall with water and the solution again evaporated to release vapors of sulphuric anhydride. After cooling in a glass add 150−200 cmof water, filter the recovered gold through the filter (the white ribbon) and washed 4−5 times with hot water. The filter is dried, incinerated, and calcined.