GOST 23862.21-79
GOST 23862.21−79 Lanthanum, samarium, europium, gadolinium, dysprosium, thulium, ytterbium, yttrium and their oxides. Method of determining chromium (Change No. 1)
GOST 23862.21−79
Group B59
INTERSTATE STANDARD
LANTHANUM, SAMARIUM, EUROPIUM, GADOLINIUM, DYSPROSIUM, THULIUM, YTTERBIUM, YTTRIUM AND THEIR OXIDES
Method for the determination of chromium
Lanthanum, samarium, europium, gadolinium, dysprosium, thulium, yterbium, yttrium and their oxides. Method of chromium determination
ISS 77.120.99
AXTU 1709
Date of introduction 1981−01−01
The decision of the State Committee USSR on standards on October 19, 1979 N 3989 date of introduction is established 01.01.81
Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)
EDITION with Change No. 1, approved in April 1985 (IUS 7−85).
This standard establishes the colorimetric method of determining chromium (from 3·10% to 5·10
%) in Lantana, Samaria, europium, gadolinium, dysprosium, tuliya, ytterbium, yttria and their oxides.
The method is based on the reaction of chromium (VI) with diphenylcarbazide after oxidation of chromium to chromate-ion with permanganate. Chromium find visually comparing the color intensity of the analyzed solution with a color intensity of the solutions comparison.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 23862.0−79.
2. APPARATUS, REAGENTS AND SOLUTIONS
Cylinders for colorimetrically of colorless glass with ground stoppers with a height of 360 mm and a diameter of 12 mm.
Glasses glass with a capacity of 50 and 100 cm.
Watch-glasses.
Bead glass.
Tile electric.
Nitric acid of high purity according to GOST 11125−84, diluted (1:1).
Sulfuric acid of high purity according to GOST 14262−78; 0.1 mol/DMsolution.
Potassium permanganate according to GOST 20490−75, a solution with a concentration of 5 g/DM.
Sodium atomistically according to GOST 4197−74, a solution with a concentration of 2 g/DM.
Diphenylcarbazide for NTD, a solution with a concentration of 10 g/lin acetone (store in a dark bottle for no more than 3 days).
Distilled water GOST 6709−72, is further distilled in a quartz apparatus.
Potassium dichromate according to GOST 4220−75, dried to constant weight at a temperature of 140 °C.
Standard solution of chromium (VI) (spare) containing 0.1 mg/cmchrome: 0,283 g of potassium dichromate dissolved in water and bring the volume of solution in a volumetric flask with a capacity of 1000 cm
to the mark with water.
A solution of chromium (VI) containing 1 µg/cmchromium, prepared by dilution of a standard (fallback) solution of chromium water 100 times. The solution is prepared the day of use.
Sec. 2. (Changed edition, Rev. N 1).
3. ANALYSIS
3.1. A portion of the sample weighing 2 g were placed in a glass with a capacity of 100 cm, 10−12 cm pour
nitric acid, diluted 1:1 and dissolved by heating on a hot plate. The resulting solution is evaporated to crystallization of salts, then dissolved in 15 cm
of 0.1 mol/DM
sulfuric acid and poured 15 cm
of water. In a glass of solution is placed a glass bead, covered with a glass watch glass and heat the solution to boiling. Add two drops of solution of potassium permanganate and boil for 5 minutes (this solution should keep the pink color). In the boiling solution poured dropwise (with an interval of approximately 5 C) solution of sodium attestatio until complete disappearance of the pink color caused by the presence of the permanganate ion, continue to boil for another 5 min (attestatio excess sodium should be avoided). The contents of the glass rapidly cooled to room temperature and immersing the glass into cold water, remove the watch glass, add 1 cm
of a solution of diphenyl-carbazide and transfer the solution into the cylinder to colorimetrically. The volume of solution in the cylinder was adjusted with water to 30 cm
and mixed.
The intensity of the color is compared on white background with the color intensity of the solutions scale comparison, watching the painting from top to bottom.
Simultaneously with the analysis of the sample carried through all stages of the analysis of the audit experience of the reagents. The amount of chromium in a control experiment should not exceed 0,02 g
.
3.2. Preparation of the scale comparison
In glasses with a capacity of 50 cmpour 15 cm
of 0.1 mol/DM
solution of sulphuric acid, 15 cm
water, 1 cm
of solution difenilcarbazida and administered 0; 0,02; 0,05; 0,10; 0,20; 0,30; 0,50; 0,70; 1,0 cm
of a solution of chromium (VI) (containing 1 µg/cm
chromium). The beaker contents stirred after each addition of the reagent.
The solutions were transferred into the cylinders to colorimetrically.
The scale comparison is prepared simultaneously with the samples.
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of chromium () in percent is calculated by the formula
where is the mass of chromium in the sample, µg;
is the mass of chromium in a control experiment, µg;
— the weight of the portion of the sample,
The result of the analysis take the average of results of two parallel measurements.
4.2. Discrepancies in the results of two parallel determinations or the results of the two tests should not exceed the values permitted discrepancies listed in the table.
| Mass fraction of chromium, % |
Allowable difference, % |
3·10 |
3·10 |
3·10 |
2·10 |
5·10 |
3·10 |
