GOST 20580.1-80
GOST 20580.1−80 (ST SEV 906−78) Lead. Methods for determination of silver (with Amendments No. 1, 2)
GOST 20580.1−80*
(ST CMEA 906−78)
Group B59
STATE STANDARD OF THE USSR
LEAD
Methods for determination of silver
Lead. Methods for the determination of silver
AXTU 1709**
________________
** Changed revision, Rev. N 2.
Date of introduction 1980−12−01
Resolution of the USSR State Committee for standards, dated April 29, 1980, N 1976 the period of validity set with 01.12.80
Proven in 1983 by the Decree of Gosstandart from
________________
** Expiration removed by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (I & C N 11, 1995). — Note the manufacturer’s database.
REPLACE GOST 20580.1−75
* REPRINT December 1984, Change No. 1, approved in December 1983 (ICS 4−84)
The Change N 2, approved and put in force by the Decision of Gosstandart of the USSR from
Change No. 2 made by the manufacturer of the database in the text IUS N 11, 1990
This standard specifies the extraction-titrimetric method for the determination of silver is from 0.0005 to 0.015% and the extraction-photometric method for the determination of silver from 0.0001 to 0.0005% of the lead (99,992−99,5%).
The standard fully complies ST SEV 906−78.
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis and security requirements — according to GOST 20580.0−80.
(Changed edition, Rev. N 2).
1.2. (Deleted, Rev. N 2).
2. EXTRACTION-TITRIMETRIC METHOD
The method is based on the extraction of silver ion with a solution of dithizone in carbon tetrachloride from a slightly acidic environment. Extraction the titration until the color of Golden yellow (dithizonate silver) red-purple (dithizonate copper). In the determination of silver by this method are used bidistillated water.
2.1. Reagents and solutions
Nitric acid GOST 4461−77 diluted 1:3, and the solutions (HNО
)=1 mol/DM
and
(HNO
)=0.1 mol/DM
.
Sulfuric acid GOST 4204−77 and diluted 1:1 and 1:99.
Ammonia water according to GOST 3760−79 and diluted 1:99.
Tartaric acid crystal according to GOST 5817−77.
Hydroxylamine hydrochloric acid according to GOST 5456−79 and a solution with a mass concentration of 10 g/DM.
Methyl red on the other 6−09−4530−77, a solution with a mass concentration of 1 g/DMin a mixture of ethanol and water 1:1.
Ethyl alcohol according to GOST 18300−72*.
_______________
* Valid GOST 18300−87. -Note the manufacturer’s database.
Carbon tetrachloride according to GOST 20288−74. In the absence of chemically pure reagent used carbon tetrachloride before use, is subjected to cleaning: a solution of hydroxylamine hydrochloric acid is neutralized with ammonia solution on methyl red. Then for every 100 cmof carbon tetrachloride was added 10 cm
of a solution of hydrochloric acid hydroxylamine. The resulting solution was transferred to a separatory funnel, mixed well and after separation of the phases, the lower organic phase was drained. The treatment is repeated two times. The thus purified carbon tetrachloride is distilled from the flask with an efficient reflux condenser on a water bath, collecting the fraction with a boiling point of 76.7 per-77,2 °C.
Dicison on the other 6−09−07−1684−89; for the preparation of the purified reagent take of 0.52 g of dithizone, crushed to powder and dissolved in 100 cmof carbon tetrachloride. The insoluble residue was filtered. The filtrate is transferred to a separatory funnel with a capacity of 500 cm
and extracted several times 100 cm
of ammonia solution (1:99), while the last portion of the ammonia extract becomes colorless. Ammonia to the filtrate add a solution of sulfuric acid (1:1) until complete precipitation of dithizone (until discoloration of the solution). Dark ditizona the precipitate is filtered using paper filter, washed 5−6 times with distilled water and dried at 50 °C for 3−5 h. the Purified ditson keep in a dark, dry, tightly sealed container.
Solution dithizone 1:
0.05 g crushed to fine powder purified dithizone dissolved in 100 cmof carbon tetrachloride. The solution was filtered into a flask made of dark glass through a dry paper filter and dry the funnel. The solution remains for a long time if kept under a layer of sulfuric acid solution (1:99).
Solution dithizone 2:
dilute the solution dithizone 1 (1 cmof this solution contains 0.5 mg of ditizone) of carbon tetrachloride. The titer of the solution is determined by standard solution of silver. 1 cm
of a solution of dithizone 2 should be 3 to 3.5 g of silver. The solution is prepared before use.
To determine the titer of a solution of dithizone in a separating funnel with a capacity of 50 cmpipetted 2 cm
of silver solution Used, add 2.5 cm
of a solution of nitric acid of concentration 1 mol/DM
, 25 cm
of water and stirred. To a solution of microburette add 2cm
of a solution of dithizone 2 and extracted within 2 min. After the separation of the organic solvent, painted dithizonate silver in the Golden-yellow color, is poured into a test tube. To the solution in separating funnel add 2 cm
of a solution of dithizone 2 and repeat the extraction of silver, merging the organic layer to another tube. Extraction of silver by solution of dithizone continue in portions of 1 cm
up until the last portion will not retain its green color.
After the first tentative titration is carried out a second, more accurate titration. To do this, when approaching the equivalent of point extraction of silver ions is carried out in portions of 0.2 cmsolution dithizone 2 up until the last portion will not retain its green color. Sometimes the penultimate portion of dithizone has a mixed color due to the presence of dithizonate of silver and excess of a solution of dithizone.
To calculate the titer of a solution of dithizone take into account the total volume of the solution of dithizone spent on education dithizonate silver. If the penultimate portion is painted in mixed color, count half or quarter (depending on the prevailing shade of color) of the volume of the penultimate portions (0.1 or 0.05 cm).
The titer of a solution of dithizone in g/cm
of silver calculated by the formula
where — weight of silver taken for titer determination, g;
— the volume of solution dithizone consumed for titration of silver cm
.
Silver nitrate according to GOST 1277−75.
Standard solutions of silver.
Solution a: 0,158 g of silver nitrate dissolved in 20 cmof a solution of nitric acid 0.1 mol/DM
, is transferred into a measuring flask with volume capacity of 1000 cm
, is diluted to the mark with the same acid and mix.
1 cmof solution A contains 0.1 mg of silver.
Solution B: in a volumetric flask with a capacity of 100 cmpipetted 10 cm
of solution A, dilute to the mark with nitric acid solution of concentration 0.1 mol/l
and stirred.
1 cmof a solution contains 0.01 mg of silver.
(Changed edition, Rev. N 1, 2).
2.2. Analysis
A portion of lead with a mass of 10.00 g (at a mass proportion of silver is from 0.0005 to 0.002%) or 2,000 g (at a mass fraction of silver from 0.002 to 0.015%) dissolved in the glass in respectively 50 and 20 cmof nitric acid (1:3). The solution was transferred to a volumetric flask with a capacity of 100 cm
. After cooling, the solution was diluted to the mark with water and mix. To determine the silver select 25 cm
and the solution is evaporated almost to dryness. To the residue add 3 cm
of a solution of nitric acid of concentration 1 mol/DM
, gently warmed, add 20 cm
of water, 0.1 g of tartaric acid and heated until complete dissolution of salts. When the mass fraction of antimony and tin in excess of 0.01% tartaric acid in an amount of 0.5 g is added at the beginning of decomposition. After cooling, the solution is transferred to a separatory funnel with a capacity of 50 cm
, the glass is washed 2−3 times in 10 cm
of water and the washing water added to the main solution.
To the solution in separating funnel from microburette pour 2 cmof a solution of dithizone 2 and shaken for 2 min. Give liquids to decompose and the organic layer containing dithizone silver Golden yellow color, poured into a test tube. To the aqueous solution in a separating funnel add 2 cm
of a solution of dithizone 2 and repeat the extraction, collecting the organic layer to another tube. Further extraction is carried out in portions of 1 cm
of a solution of dithizone 2 until you see the red-purple staining of the organic layer (a sign of the beginning of copper extraction).
After this first approximation of consumption ditizona carry out a more careful titration of silver in the other sample, and the closer to the equivalent point for the extraction of the last quantities of silver solution dithizone added in portions of 0.2 cm.
To calculate the results of the analysis take into account the total volume of the solution of dithizone spent on education dithizonate silver. If after the extraction, the solution will be painted in pure red-violet color, and mixed, then, depending on the prevailing tone of color count half or quarter the penultimate portions of the solution of dithizone spent on education mixed colour of the organic layer.
The analysis on silver all used reagents and solutions should be checked for the absence of chlorides.
(Changed edition, Rev. N 1, 2).
2.3. Processing of the results
2.3.1. Mass fraction of silver in percent is calculated by the formula
where is the volume of solution dithizone spent on the extraction of silver, cm
;
the titer of a solution of dithizone, g/cm
of silver;
— the solution volume, cm
;
— the weight of the portion of the lead, g;
— volume aliquote part of the solution, cm
.
2.3.2. Allowable absolute discrepancies in the results of parallel measurements and the results of the analysis shall not exceed the values given in table.1.
Table 1
| Mass fraction of silver, % |
The allowable divergence of the parallel definitions % |
Permissible discrepancies in the results of the analysis % |
| Between 0.0005 and 0.0015 incl. |
0,0002 | 0,0003 |
| SV. 0,0015 «0,0025 « |
0,0003 |
0,0004 |
| «0,0025» 0,0050 « |
0,0005 |
About 0.0006 |
| «0,0050» 0,0100 « |
0,0008 |
0,0010 |
| «Of 0.010» to 0.015 « |
0,001 |
0,002 |
(Changed edition, Rev. N 2).
3. EXTRACTION-PHOTOMETRIC METHOD
The method is based on extraction of silver ions in a weakly acid medium with a solution of dithizone in carbon tetrachloride with subsequent extrapyramidal hydrochloric acid and repeating the extraction of silver from aqueous solution at pH 5 in the presence of EDTA. Definition of silver by the method of performing monochrome color at a wavelength of 460 nm. For analysis use bidistillated water.
3.1. Apparatus, reagents and solutions
Spectrophotometer or photoelectrocolorimeter of any kind for measurements in the visible region of the spectrum.
Sulfuric acid GOST 4204−77, a solution of (
SO
)=1 mol/l
and diluted 1:99.
Hydrochloric acid by the GOST 3118−77, solution (Hcl)=1 mol/DM
.
Ammonia water according to GOST 3760−79 diluted 1:1, 1:3 and 1:99.
Nitric acid GOST 4461−77, solutions (HNO
)=0.1 mol/DM
and
(HNO
)=0,003 mol/l
and diluted 1:3.
Ethylenediamine-N, N, N, N'-tetraoxane acid disodium salt, 2-water (EDTA) according to GOST 10652−73, a solution with a mass concentration of 100 g/DM.
Acetic acid GOST 61−75.
Buffer solution with pH 5: 47 cmof acetic acid are mixed with 103 cm
of ammonia solution (1:3) and 100 cm
of water.
Carbon tetrachloride according to GOST 20288−74 purged according to claim 2.1.
Dicison on the other 6−09−07−1684−89.
Solution dithizone 1: 0.05 g crushed to fine powder purified dithizone dissolved in 100 cmof carbon tetrachloride. The solution was filtered into a flask made of dark glass through a dry filter and dry the funnel. The solution remains for a long time if kept under a layer of sulphuric acid (1:99).
Dithizone solution with a mass concentration of 0.05 g/DMfreshly prepared: diluted solution of dithizone 1 of carbon tetrachloride.
Silver nitrate according to GOST 1277−75.
Standard solutions of silver.
Solution a: 0,158 g of silver nitrate dissolved in 20 cmof nitric acid solution of concentration 0.1 mol/DM
, is transferred into a measuring flask with volume capacity of 1000 cm
, is diluted to the mark with the same solution of nitric acid and stirred.
1 cmof solution A contains 0.1 mg of silver.
Solution B: in a volumetric flask with a capacity of 1000 cmpipetted 10 cm
of solution A, dilute to the mark with nitric acid solution of concentration 0.1 mol/l
and stirred.
1 cmof the solution contains 0.001 mg of silver.
(Modified re
Doccia, Rev. N 1, 2).
3.2. Analysis
3.2.1. The weight of the portion selected depending on the mass fraction of silver (tab.2), is dissolved in 50 cmof nitric acid (1:3), the solution was evaporated to dryness, the residue is dissolved in 30 cm
of water, transferred to a separatory funnel, establish a pH of 2.0 and extracted three times silver (along with bismuth and copper) ditizone solution with a mass concentration of 0.05 g/l
in carbon tetrachloride in portions of 4 cm
.
Table 2
| Mass fraction of silver, % |
The mass of charge, g |
| 0,0001 |
5,000 |
| 0,0002 |
3,000 |
| 0,0003 |
2,000 |
| 0,0004 |
2,000 |
| 0,0005 |
1,000 |
The extract is washed three times with a solution of nitric acid concentration of 0.003 mol/DMand extravert bismuth 10 cm
of sulfuric acid solution
(
I
)=1 mol/DM
. The organic phase is shaken with 10 cm
of hydrochloric acid of concentration 1 mol/DM
to the aqueous solution add diluted ammonia solution (1:1) to pH 4−5 by universal indicator paper, then 2 cm
of EDTA solution, 2 cm
of buffer solution and extracted silver 4 cm
solution dithizone in carbon tetrachloride. Excess dithizone washed free of extract with ammonia solution (1:99) by shaking with two portions of 5 cm
. The last portion of wash solution should be colorless; if it has a yellowish tint, wash, repeat. The optical density of the solution is determined at a wavelength of 460 nm. Solution comparison is the solution of carbon tetrachloride. Before defining optical density for the removal of water the organic layer was filtered through a dry paper filter.
(Changed edition, Rev. N 1, 2).
3.2.2. For construction of calibration curve six separatory funnels were placed, respectively 1,0; 2,0; 3,0; 5,0; 6,0 and 10,0 cmstandard silver solution B. the Seventh funnel is used for the reference experiment. To each funnel add water up to 10 cm
, set with ammonia of pH from 4 to 5 on the universal indicator paper, add 2cm
of a solution of EDTA, 2 cm
buffer solution and extracted silver 4 cm
dithizone solution with a mass concentration of 0.05 g/DM
. Excess dithizone washed 2 times with ammonia solution (1:99) in portions of 5 cm
. The last portion of wash solution should be colorless; if it has a yellowish tint, wash, repeat. The optical density of the solution is determined at a wavelength of 460 nm. Solution comparison is the solution of carbon tetrachloride. Before defining optical density for the removal of water the organic layer was filtered through a dry paper filter.
According to the obtained values of optical density of solutions and their corresponding silver content build the calibration graph.
The analysis on silver all reagents and solutions shall be checked for absence of chlorine.
(Changed edition, Rev. N 2).
3.3. Processing of the results
3.3.1. Mass fraction of silver in percent is calculated by the formula
where is the mass of silver was found in the calibration schedule g;
— the weight of the portion,
3.3.2. Allowable absolute discrepancies in the results of parallel measurements and the results of the analysis shall not exceed the values given in table.3.
Table 3
| Mass fraction of silver, % |
The allowable divergence of the parallel definitions % |
Permissible discrepancies in the results of the analysis % |
| From 0,00010 to 0,00040 incl. |
0,00003 |
0,00004 |
| SV. 0,00040 «0,00050 « |
0,00005 |
Of 0.00006 |
(Changed edition, Rev. N 2).
