GOST 8775.4-87
GOST 8775.4−87 Li. Method for determination of nitrogen
GOST 8775.4−87
Group B59
STATE STANDARD OF THE USSR
LI
Method for determination of nitrogen
Lithium.
Method for determination of nitrogen
AXTU 1709
Valid from 01.07.88
to 01.07.93*
__________________________
* Limit of validity
based on a Protocol of Intergovernmental
Council for standardization, Metrology
and certification (I & C N 2, 1993). -
Note the manufacturer’s database.
INFORMATION DATA
1. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from
2. The term of the first test 1991
The frequency of inspection 5 years
3. REPLACE GOST 8775−75 (sect.5)
4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
Section number, paragraph, application |
| GOST 3773−72 |
Sec. 2 |
| GOST 4204−77 |
Sec. 2 |
| GOST 4212−76 |
Sec. 2 |
| GOST 4517−75 |
Sec. 2 |
| GOST 8774−75 |
Sec. 4 |
| GOST 8775.0−87 |
1.1; 5.2; 5.3.3; 5.4 |
| GOST 8775.1−87 |
Sec. 2 |
| GOST 10157−79 |
Sec. 2 |
| GOST 14919−83 |
Sec. 2 |
This standard sets the photometric method for determination of nitrogen with the mass fraction from 0.003 to 0.2 percent lithium.
The method is based on dissolving lithium in water, the absorption of released ammonia with sulfuric acid and measuring the optical density of colored solution after adding the help of nessler’s reagent.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 8775.0−87.
2. APPARATUS, REAGENTS AND MATERIALS
Installation for the distillation and recovery of ammonia (drawing). All parts of the installation made of glass «Pyrex» or other heat-resistant glass. The connecting rubber tubing and rubber stoppers are cleaned by boiling them in 1% strength sodium hydroxide solution followed by washing with distilled water containing no ammonia.
Drawing. Installation for the distillation and recovery of ammonia
Installation for the distillation and recovery of ammonia
1 — steam generator — bottomed flask with a capacity of 500−750 cm; 2, 9 — rubber tube;
3, 12 — rubber tube; 4, 11 — clamps; 5 — filling funnel for perelivania water;
6 — nozzle; 7 — refrigerator; 8 — receiver conical flask with a capacity of
100−250 cmwith the mark of 80−90 cm
; 10 — the branch tube; 13 — reaction flask
(Kjeldahl type) with a capacity of 250−500 cm
The unit according to GOST 14919−83 or mantle.
Photocolorimeter type FEK-56, PEC-60, KLF-2.
The chamber filled with dry argon containing not more than 0.2 g/mof moisture.
Argon according to GOST 10157−79, drained according to claim 2.3.1 GOST 8775.1−87.
Cups for weighing type SV 24/10.
Ammonium chloride according to GOST 3773−72: solution 1, containing 1 mg of nitrogen in 1cm, prepared according to GOST 4212−76; solution 2 containing 0.01 mg of nitrogen in 1 cm
, prepare a dilution solution of 1 in a hundred times.
The help of nessler’s reagent, prepared according to GOST 4517−75.
Sulfuric acid GOST 4204−77, 0.005 mol/DMsolution.
3. PREPARATION FOR ASSAY
3.1. Installation preparation and carrying out of control experience
Before analysis setup (see drawing) is washed with a steam jet for 15−20 min. Steam enters from the flask of the steam generator in which water is poured up to two thirds of the volume and 1−2 cmof concentrated sulfuric acid. Collected in a receiver about 50 cm
of the distillate. To the distillate add 1 cm
of the help of nessler’s reagent, mixed and after 10 min measure the optical density of the solution on photocolorimetry according to claim
3.2. Establishing calibration characteristics
3.2.1. In a volumetric flask with a capacity of 50 cmis placed 1,0; 2,0; 3,0; 4,0; 5,0 cm
solution of 2, that corresponds to the content in colorimetrically solutions of 0.01, 0.02… 0.05 mg of nitrogen, add 2.5 cm
of sulfuric acid solution, dilute with water to half the volume of the flask, mix, add 1 cm
of the help of nessler’s reagent. The volume of the solutions was adjusted to the mark with water and mix again. At the same time prepare a solution of comparison containing all added reagents except solution 2.
3.2.2. After 10 minutes measure the optical density of solutions relative to the comparison solution at a wavelength of 440 nm in a cuvette with a light-absorbing layer thickness of 30 mm. According to the results of the photometry data to build a calibration curve, plotting the abscissa shows the mass of nitrogen in milligrams, and the y — axis the corresponding value of optical density.
Calibration curve check at least once a quarter, and in the event of a change of photocolorimetry or reagents. Each point of the graph obtained as the arithmetic mean of the results of the three measurements.
Allowed numerical linear dependence of optical density of the tested solutions of the mass contained in them of nitrogen. For this, the results of the photometry are treated by the method of least squares and represent the dependence by the formula
where a — optical density of the solution;
— the mass of nitrogen contained in the solution, mg;
,
— the numerical coefficients, determined in the calibration.
4. ANALYSIS
4.1. Bank sample of lithium stored in accordance with GOST 8774−75, placed in a chamber filled with dry argon. A piece of lithium removed from the jar with tweezers, and remove it from the surface with filter paper oil, placed on a rigid steel plate, clean the surface of the metal and cut out the middle piece with a mass of 0.5−1.5 g of lithium. The cut piece is placed into a pre-weighed Cup with a sealing lid. Remove the Cup from the chamber and weighed.
Permitted clearing of a surface of lithium and weighing the cut piece to produce the air. In this case, the weighting is carried out after cleaning and cutting the piece of metal within 5 min.
The receiver 8 is poured 10 cmof sulphuric acid. The tip of the refrigerator 7 is immersed in acid. In the funnel 5 pour 50 cm
of water. Open the clamp on the outlet 11 of the tube 10 and closing the clip 4.
4.2. A portion of lithium is placed in a dry Kjeldahl flask, connect the flask quickly to the distillation apparatus for ammonia. Through the funnel 5 into the flask 13 pour the water in small portions. After the dissolution of the sample 4 open the clamp and close the clamp 11. Distillation of ammonia is produced as long as the receiver is not received 80−90 cmdistillate.
The contents of the receiver is transferred to a volumetric flask with a capacity of 100 cm, wash the sink with water and bring the volume of solution in a volumetric flask to the mark with water.
4.3. Aliquot part of the solution is 5−25 cm(depending on the nitrogen content) was placed in a volumetric flask with a capacity of 50 cm
, is diluted with water to a volume of 45 cm
, pour 1 cm
of the help of nessler’s reagent, the solution volume adjusted to the mark with water and mix. At the same time prepare a solution of comparison: in a volumetric flask with a capacity of 50 cm
is placed 0.5−2.5 cm
of sulphuric acid (depending on aliquote parts), dilute with water to 45 cm
, pour 1 cm
of the help of nessler’s reagent, was adjusted to the mark with water and mix.
5. PROCESSING OF THE RESULTS
5.1. Mass fraction of nitrogen (a) percentage calculated by the formula
where is the total volume of the analyzed solution, cm
;
— aliquota part of the solution, cm
;
— the weight of lithium, g;
— weight of nitrogen, mg, mounted on a calibration schedule or calculated according to the formula
where a — optical density of the analyzed solution;
,
— the numerical coefficients defined by the formula (1).
5.2. For the results analysis be the arithmetic mean of two parallel definitions (some definitions) under the conditions of the PP.2.5, 2.6, and 2.10 GOST 8775.0−87.
5.3. Accuracy metrics
5.3.1. Indicators of convergence and reproducibility definitions — () and (
) and error values of analysis results (
) listed in the table.
| Mass fraction of nitrogen, % |
| ||
| no more | |||
3·10 |
0,13 |
0,20 |
8·10 |
6·10 |
0,09 |
0,12 |
1·10 |
4·10 |
0,04 |
0,06 |
3·10 |
5.3.2. Non-excluded systematic error () is insignificant compared to the random error.
5.3.3. The value of error analysis result () is determined according to GOST 8775.0−87.
5.4. The control accuracy of the analysis
The control accuracy of the analysis carried out by the method of additives in accordance with GOST 8775.0−87, as a Supplement, use a solution of ammonium chloride containing 0.01 mg of nitrogen in 1 cm(solution 2).
The additive is introduced into a portion of the sample through the filling funnel 5 to the beginning of the dissolution test.
