GOST 741.9-80
STATE STANDARD OF THE USSR
COBALT
METHOD FOR THE DETERMINATION OF ARSENIC
COBALT
Method for the determination of arsenic
GOST 741.9−80
Group B59
AXTU 1709
(code AXTU introduced by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Replace GOST 741.9−69
The validity of
from July 1, 1981
prior to July 1, 1986
This standard sets the photometric method for the determination of arsenic from 0.0001 to 0.01%.
The method is based on measuring the light absorption of the blue form arsenic-molybdenum complex at a wavelength of 610 nm after prior separation of arsenic by coprecipitation with iron hydroxide and extraction godenovo complex with carbon tetrachloride.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 741.1−80.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
2. APPARATUS, REAGENTS AND SOLUTIONS
Photoelectrocolorimeter or spectrophotometer of any type.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
Nitric acid of high purity according to GOST 11125−84, density of 1.38 g/cm3, and diluted 1:1.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
Sulfuric acid GOST 4204−77, diluted 1:3 and 1:10 solutions of 0.5 and 3 M.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Hydrochloric acid according to GOST 14261−77, solutions of 1:1 and 9 M; hydrochloric acid free from arsenic and contain 20 g/dm3 potassium iodide.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
The acid is purified from arsenic in the following manner: in 500 cm3 of hydrochloric acid dissolve 10 g of potassium iodide. The solution was transferred to a separatory funnel with a capacity of 1 dm3, is added to 25 cm3 of carbon tetrachloride and shaken for 2 min. the Organic layer discarded after settling. Add 25 cm3 of carbon tetrachloride, shake again 2 minutes and again discard the organic layer. Cleaning acid is carried out in day of application.
(in edition of Changes No. 1, promulgated by the Decree of Gosstandart of the USSR from
Rectified ethyl alcohol according to GOST 18300−72.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Ammonia water according to GOST 3760−79 distilled.
Ammonium molybdate according to GOST 3765−78, a solution of 10 g/DM 3 sulfuric acid solution 3 M Molybdate, ammonium is twice recrystallized from alcohol solution: 70 g of salt are dissolved in 400 cm3 of hot water and twice filtered through a dense filter. To the solution was added to 250 cm3 of ethanol and, after 1 h of settling, the crystals are suctioned funnel Buchner. The obtained molybdate ammonium solution, and again recrystallized. The crystals are filtered off, washed several times with water and with alcohol and dried in air.
(in edition of Changes No. 1, promulgated by the Decree of Gosstandart of the USSR from
Hydrazine sulfate according to GOST 5841−74, a solution of 1.5 g/dm3.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Hydrazine — molybdate solution: in a volumetric flask with a capacity of 100 cm3 taken 50 cm3 of a solution of molybdate of ammonium, pour 5 cm3 of a solution of sulphate of ammonium and topped to the mark with water.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
The iron powder according to GOST 9849−86.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
A solution of nitrate of iron: 1.00 g of iron powder are dissolved in 20 cm3 of nitric acid solution, transferred to a volumetric flask with a capacity of 100 cm3 and topped to the mark with water.
(paragraph added by the Change in N 2, approved. By the decree of Gosstandart of the USSR from
1 cm3 of the solution contains 1 x giron.
(paragraph added by the Change in N 2, approved. By the decree of Gosstandart of the USSR from
Sodium carbonate crystal according to GOST 84−76, saturated solution.
Sodium hydroxide according to GOST 4328−77, 1 M solution.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Potassium iodide according to GOST 4232−74.
Potassium permanganate according to GOST 20490−75, 0.06 M solution.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Ammonium chloride according to GOST 3773−72, a solution of 20 g/dm3
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Carbon tetrachloride according to GOST 20288−74 distilled.
Titanium trichloride on the other 6−09−01−756−88.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
The paragraph is excluded from 1 may 1992. — Amendment No. 2, approved. By the decree of Gosstandart of the USSR from
The oxide of arsenic As (III).
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
Standard solutions of arsenic
Solution A: 0,1320 g of the oxide of arsenic As (III) dissolved in 5 cm3 of sodium hydroxide solution, dilute with water to volume of 50 cm3, flow 6 cm3 of 0.5 M sulfuric acid solution, transferred to a volumetric flask with a capacity of 500 cm3 and topped to the mark with water.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
1 cm3 of solution A contains 2 g of arsenic.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Solution B: 25 cm3 of solution A is taken in a volumetric flask with a capacity of 500 cm3 and topped to the mark with water.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
1 cm3 of solution B contains 1 g of arsenic.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
3. ANALYSIS
3.1. A portion of the cobalt is dissolved in nitric acid solution under heating. The size of the sample and the quantity of nitric acid, depending on the mass fraction of arsenic are given in table. 1.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
Table 1
────────────────────────┬───────────────────┬─────────────────────
Mass fraction of arsenic, %│ Mass of sample, g │ Volume nitrogen
│ │ acid, cm3
────────────────────────┼───────────────────┼─────────────────────
From 0,0001 to 0,0003 │10 │70
SV. The 0.0003 «to 0.0005 │5 │60
«Of 0.0005» to 0.001 │3 │50
«Of 0.001» to 0.002 │1 │30
«Of 0.002» to 0.005 │0,5 │25
«0,005» 0,01 │0,25 │25
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
The dissolution is carried out in beakers with a capacity of 500 cm3. After dissolution, the sample solution volume was adjusted with water to 300 cm3, pour 1 cm3 of a solution of nitrate of iron and the precipitated iron hydroxide ammonia solution or a saturated sodium carbonate solution at pH 3.5 — 4. The solution with the sediment bring to the boil and leave in a warm place for 40 minutes to coagulate.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
The precipitate was filtered off, washed with a solution of ammonium chloride and perioada hydroxides with ammonia. The precipitate was allowed to stand a warm place for 30 min., filtered off, washed with hot water and dissolved in 25 cm3 of hydrochloric acid diluted 1:1, collecting the filtrate in a beaker, in which was conducted the deposition. For reduction of iron and arsenic in the glass is added dropwise a solution of titanium trichloride to a bleaching solution and 1 — 2 drops in excess.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
The solution was transferred to a separatory funnel with a capacity of 250 cm3, pour three times the volume of purified concentrated hydrochloric acid, add 30 cm3 of carbon tetrachloride and extracted within 2 min. the Organic layer drained into another separating funnel, and in the first add 15 cm3 of carbon tetrachloride and repeat the extraction.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
The combined organic extracts are washed for 20 with 20 cm3 of 9 M hydrochloric acid solution, and then to the organic layer, pour 15 cm3 of water and carry out the Stripping of arsenic for 2 min. then separated the organic layer and repeat the Stripping under the same conditions. Water layers merge into a measuring flask with volume capacity of 50 cm3, add dropwise a solution of potassium permanganate until a stable pink colour, which is then destroyed, priliva drip solution of hydrazine sulfate. Then add 4 cm3 of freshly prepared gidratirovannogo solution and place the flask in a boiling water bath for 15 min.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
The solution was cooled, made up to the mark with water and measure the light absorption of the solution at a wavelength of 610 nm. As a solution comparison, use water.
(in edition of Changes N 2, approved. By the decree of Gosstandart of the USSR from
Simultaneously with the breakdown of spend control experience. From the found values of absorbance of the analyzed solution is subtracted the value of the absorption solution in the reference experiment.
(in edition of Changes N 2, approved. By the decree of Gosstandart of the USSR from
The mass of arsenic in the analyzed solution found by the calibration schedule, adjusted for the weight of the arsenic in solution in the reference experiment.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
3.2. The construction of the calibrationgraph
In a volumetric flask with a capacity of 50 cm3 is taken 0; 0,50; 1,00; 1,50; 2,00; 2,50; 3,00 cm3 of standard solution B, which corresponds to (0; 0,005; 0,010; 0,15; 0,020; 0,025; 0,030) x g of arsenic, dilute with water to 40 cm3 and further in accordance with sec. 3.
According to the obtained values of absorption and their corresponding mass of phosphorus build a calibrationchart.
(paragraph 3.2 as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of arsenic (X) in percent is calculated by the formula
,
where is the mass of arsenic, was found in the calibration schedule g;
m — weight of cobalt, g.
4.2. Allowable absolute discrepancies in the results of parallel measurements characterizing the convergence of the method (d), and the results of two analyses that characterize the reproducibility of the method (D), shall not exceed the values specified in table. 2.
Table 2
───────────────────────────┬──────────────────────────────────────
Mass fraction of arsenic, % │allowable Absolute differences, %
├───────────────────┬──────────────────
│ d │ D
───────────────────────────┼───────────────────┼──────────────────
From 0,0001 to 0,0003 incl.│ Of 0.00006 │ 0,00009
SV. 0,0003 «to about 0.0006» resolution of 0,0001 │ 0,0001
«0,0006» 0,0012 «│ 0,0002 │ 0,0002
«0,0012» 0,0030 «│ 0,0005 │ 0,0006
«0,003» 0,006 «│ 0,001 │ 0,001
«0,006» 0,010 «│ 0,002 │ 0,002
(paragraph 4.2 as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
