GOST 20580.5-80
GOST 20580.5−80 (ST SEV 910−78) Lead. Method for the determination of arsenic (with Amendments No. 1, 2)
GOST 20580.5−80*
(ST CMEA 910−78)
Group B59
STATE STANDARD OF THE USSR
LEAD
Method for the determination of arsenic
Lead. Method for the determination of arsenic
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 20580.5−75
* 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 sets the photometric method for the determination of arsenic from 0.0002 to 0.1% in the lead (99,992−99,5%).
The method is based on the interaction of pentavalent arsenic with an anion molybdate and getting michalopolous acid, which is extracted with a mixture of butyl alcohol and ether. Myrzakulova acid recovered in organic extract dichloride tin to molybdenum blue and the resulting organic solution photometered in the region of wavelengths of 610−700 nm. To obtain michalopolous acid and its full extraction is required in the solution of the hydrochloric acid concentration was 0.6 to 1.2 mol/DM.
The standard fully complies ST SEV 910−78.
(Changed edition, Rev. N 1).
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis and security requirements — according to GOST 20580.0−80.
(Changed edition, Rev. N 2).
1.2. (Deleted, Rev. N 2).
2. APPARATUS, REAGENTS AND SOLUTIONS
Spectrophotometer or photoelectrocolorimeter of any kind for measurements in the visible region of the spectrum.
Nitric acid GOST 4461−77 and diluted 1:2.
Hydrochloric acid by the GOST 3118−77 and solution (Hcl)=1.5 mol/DMand (Hcl)=1 mol/DM.
Ammonia water according to GOST 3760−79.
Sodium molybdate according to GOST 10931−74, a solution with a mass concentration of 15 g/DM.
Secondary butyl alcohol on the other 6−09−4620−78.
The ethyl ether.
The mixture of extraction: secondary butyl alcohol is mixed with ether in the ratio 2:1.
Tin (II) chloride on the other 6−09−5384−88, a solution with a mass concentration of 2 g/lsolution of hydrochloric acid of concentration 1 mol/DM, freshly prepared.
Methyl orange on the other 6−09−5171−84, a solution with a mass concentration of 5 g/DM.
Potassium branovitsky according to GOST 4457−74, solution (KBrO)=0.05 mol/DM(approx.)
Sodium hydroxide according to GOST 4328−77, a solution with a mass concentration of 20 g/DM.
The oxide of arsenic (III) according to GOST 1973−77.
Standard solutions of arsenic.
Solution a: 0,132 g of the oxide of arsenic (III) dissolved in 20 cmof sodium hydroxide solution. The solution is transferred into a measuring flask with volume capacity of 1000 cm, acidified with hydrochloric acid, made up to the mark with water and mix.
1 cmof solution A contains 0.1 mg of arsenic.
Solution B: 5 cmsolution And add 1 cmof hydrochloric acid, 1 drop of methyl orange solution, heated to 60−70 °C and added dropwise a solution of potassium polnovatogo to the disappearance of color of methyl orange. The solution was transferred to a volumetric flask with a capacity of 100 cm, cooled to room temperature, made up to the mark with hydrochloric acid of concentration 1.5 mol/land stirred.
1 cmof a solution contains 0.005 mg of arsenic.
(Changed edition, Rev. N 1, 2).
3. ANALYSIS
3.1. Depending on the expected mass fraction of arsenic you take charge, the mass of which are shown in table.1.
Table 1
Mass fraction of arsenic, % |
The mass of charge, g |
The volume aliquote part of the solution, cm |
From 0,0002 to 0,001 |
5,000 |
20 |
SV. Of 0.001 «to 0.003 to |
5,000 |
10 |
«Of 0.003» to 0.005 |
2,000 |
10 |
«0,005» 0,01 |
1,000 |
10 |
«To 0.01» to 0.05 |
1,000 |
3 |
«0,05» 0,1 |
0,500 |
2 |
Table 1 (Revised edition, Edit. N 2).
A portion of the lead dissolved in 20 or 10 cmof nitric acid (1:2) and heated to remove oxides of nitrogen. The resulting solution was neutralized with aqueous ammonia to obtain a precipitate of hydroxide of lead, not disappearing under stirring, and added dropwise nitric acid to dissolve the residue. Poured 12 cmof hydrochloric acid, transferred to a volumetric flask with a capacity of 100 cm, cooled to room temperature, dilute to the mark with water and mix. The solution is filtered through a dry filter into a dry beaker.
For analysis taken in a glass aliquot part of the solution (table.1) containing from 2 to 15 µg of arsenic, add 1 drop of methyl orange solution, heated to 60−70 °C and poured dropwise a solution of potassium polnovatogo to the disappearance of color of methyl orange. The solution was cooled and transferred to a separatory funnel with a capacity of 100 cm. If the volume of the solution is less than 20 cm, pour a solution of hydrochloric acid of concentration 1.5 mol/DMup to 20 cm. Add 10 cmof a solution of molybdate of sodium, stirred and shaken with 10 cmof the extraction mixture for 20 s. the Extraction was repeated with 10 cmof the mixture. Both combine organic extract to another separating funnel with a capacity of 100 cmand washed 2 times by repeated dilution with 10 cmof hydrochloric acid of concentration 1 mol/DMto remove excess molybdate sodium. To the washed organic extract is poured 10 cmof a solution of tin chloride (II), and stirred several times. After separation of the phases the lower aqueous layer is discarded and the upper organic layer is coloured blue, transferred to a volumetric flask with a capacity of 25 cm. Separatory funnel rinsed 2 cmof the extraction mixture by collecting the washing mixture in the same volumetric flask. Diluted to the mark volume of the extraction mixture and mix.
Part of the solution is filtered over a dry filter (for the separation of droplets of moisture) into the appropriate cuvette, and after 15 minutes, counting the time from the addition of a solution of chloride of tin, measure the optical density of the solution in the region of wavelengths of 650−670 nm. Solution comparison is the extraction mixture. At the same time carried out control experiments with all reagents and solutions used in the implementation of the determination and under the same conditions. The amount of arsenic in kalorimetricheskim volume set calibration schedule.
(Changed edition, Rev. N 1, 2).
3.2. To build a calibration curve in seven separating funnels placed at 10 cmof hydrochloric acid of 1.5 mol/DMand in six of the seven funnels poured 0,5; 1,0; 1,5; 2,0; 2,5 and 3,0 cmstandard solution B. the Seventh funnel is used for the reference experiment. All funnels dilute the volume up to 20 cmof hydrochloric acid of concentration 1.5 mol/DM, add 10 cmof a solution of molybdate of sodium, and then do as stated in claim 3.1.
According to the obtained values of optical density of solutions and their corresponding mass fractions of arsenic build the calibration graph.
(Changed edition, Rev. N 1, 2).
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of arsenic , in percent calculated by the formula
,
where is the mass of arsenic, was found in the calibration schedule g;
— volume of initial solution, cm;
— the weight of the portion of the lead, g;
— volume aliquote part of the solution, cm.
4.2. Allowable absolute discrepancies in the results of parallel measurements and the results of the analysis shall not exceed the values given in table.2.
Table 2
Mass fraction of arsenic, % |
The allowable divergence of the parallel definitions % |
Permissible discrepancies in the results of the analysis % |
From of 0.0002 to 0.0008 inch incl. |
0,0001 |
0,0001 |
SV. 0,0008 «0,0030 « |
0,0003 |
0,0004 |
«0,0030» 0,0050 « |
About 0.0006 |
0,0008 |
«0,0050» 0,0100 « |
0,0010 |
0,0013 |
«0,010» 0,030 « |
0,002 |
0,003 |
«0,030» 0,050 « |
0,003 |
0,004 |
«0,050» 0,100 « |
0,005 |
0,006 |
(Changed edition, Rev. N 2).