GOST 23862.22-79
GOST 23862.22−79 Praseodymium, neodymium, terbium, holmium, erbium and their oxides. Method of determining chromium (Change No. 1)
GOST 23862.22−79
Group B59
INTERSTATE STANDARD
PRASEODYMIUM, NEODYMIUM, TERBIUM, HOLMIUM, ERBIUM AND THEIR OXIDES
Method for the determination of chromium
Praseodymium, neodymium, terbium, holmium, erbium and their oxides. Method of determination of chromium
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 for the determination of chromium (from 5·10
% to 5·10
%) in the praseodymium, the neodymium, terui, holmium, arbie and their oxides.
The method is based on extraction of chromium (VI) diphenylcarbazide isoamylase alcohol and then Stripping the painted compounds diluted sulfuric acid. 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
Tile electric.
Volumetric flasks with a capacity of 500 cm
.
Glasses with a capacity of 100 cm.
Separating funnel with a capacity of 50 cm.
Watch-glasses.
Set of cylinders for colorimetrically of colorless glass with a diameter of 6 mm, height 100 mm, with ground stoppers.
Bead glass.
Nitric acid of high purity according to GOST 11125−84; 7 mol/DMsolution.
Sulfuric acid of high purity according to GOST 14262−78; 0.1 and 0.2 mol/DMsolutions.
Potassium permanganate according to GOST 20490−75, h, a solution with a concentration of 5 g/DM.
Sodium atomistically according to GOST 4197−74, H. h, solution with a concentration of 2 g/DM.
Diphenylcarbazide for NTD, a solution with a concentration of 10 g/lin acetone (can be stored in a dark bottle for three days).
Isoamyl alcohol according to GOST 5830−79, h.d. a.
Sodium chloride according to GOST 4233−77.
Potassium dichromate according to GOST 4220−75, H. h, dried to constant weight at 140 °C.
Standard solution of chromium (spare) containing 0.1 mg/cmchrome; 0,1414 g of potassium dichromate was dissolved in a volumetric flask with a capacity of 500 cmand was adjusted to the mark with water.
The chromium solution containing 1 µg/cmchromium, prepared by dilution of a standard solution of chromium (spare) 100 times with water on the day of use.
The water is deionized.
Sec. 2. (Changed edition, Rev. N 1).
3. ANALYSIS
3.1. A portion of the metal or oxide REE weight of 2 g were placed in a glass with a capacity of 100 cm, 7−12 cm pourednitric acid and heated until dissolved. The solution is evaporated almost to dryness, the residue is dissolved in 15 cmof 0.1 mol/DMsolution of sulphuric acid and add 10−15 cmof water. In a glass put the glass bead, add 1−2 drops of solution of potassium permanganate, cover the watch glass and continue to boil for ~5 min (the solution must preserve the pink color). In the boiling solution, add dropwise (with 5 s interval) attestatio solution of sodium until complete disappearance of the pink color caused by permanganate of potassium, and continue to boil for ~5 min (attestatio excess sodium should be avoided). The contents of the glass rapidly cooled to room temperature, remove the watch glass, enter 0.5 cmof the solution difenilcarbazida and 3 g of sodium chloride. After dissolution, the salt solution is transferred to a separatory funnel with a capacity of 50 cm, flow 1 cmisoamyl alcohol and vigorously shaken for 1 min. After separation the aqueous phase is discarded, in a separating funnel add 1.5−2 cmof water and gently (not shaking it) drained of water; the organic phase is transferred to a small vial for colorimetrically with a glass stopper. Stripping coloured compounds chromium difenilcarbazida spend 0.5 cm0.2 mol/DMsulphuric acid containing one drop of solution diphenylcarbazide, vigorously shaking the solution for 1 min. After delamination, the color intensity of the water layer is compared to a white background with the color intensity of the solutions of the scale of comparison. Simultaneously with the analysis of the sample carried out control experience in chemicals. The amount of chromium in a control experiment should not exceed 0.05
mcg.
3.2. Preparation of the scale comparison
In glasses with a capacity of 50 cmis placed 5 g of sodium chloride dissolved in 20 cm0.1 mol/DMsulphuric acid, add 5 cmof water and 0.5 cmof the solution difenilcarbazida. Poured 0,05; 0,10; 0,20; 0,30; 0,40; 0,50 cmof a solution of chromium (containing 1 µg/cmchrome), stirred, solution was transferred to separating funnel with a capacity of 50 cm, flow 1 cmisoamyl alcohol and vigorously shaken for 1 min. After separation the aqueous phase is discarded, in a separating funnel add 1.5−2 cmof water and carefully (no shaking) drained of water; the organic phase is transferred to a small vial with a glass stopper. Stripping coloured compounds chromium difenilcarbazida spend 0.5 cm0.2 mol/DMsulphuric acid containing one drop of solution diphenylcarbazide, vigorously shaking the solution for 1 min.
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 specimen, found on a scale of comparison, the mcg;
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, %
|
5·10 |
5·10 |
1·10 |
1·10 |
3·10 |
2·10 |
