GOST 3240.16-76
GOST 3240.16−76 magnesium Alloys. Methods of determining the amount of rare earth elements and cerium (Change No. 1)
GOST 3240.16−76
Group B59
INTERSTATE STANDARD
MAGNESIUM ALLOYS
Methods of determining the amount of rare earth elements and cerium
Magnesium alloys.
Methods for determination of sum of rare-earth elements and cerium
ISS 77.120.20
AXTU 1709
Date of introduction 1978−01−01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of aviation industry of the USSR
2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from
3. INTRODUCED FOR THE FIRST TIME
4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
Section number, paragraph |
| GOST 8.315−97 |
Sec. 5 |
| GOST 3118−77 |
Sec. 2 |
| GOST 3240.0−76 |
1.1 |
| GOST 3760−79 |
Sec. 2 |
| GOST 3773−72 |
Sec. 2 |
| GOST 4199−76 |
Sec. 2 |
| GOST 4204−77 |
Sec. 2 |
| GOST 4208−72 |
Sec. 2 |
| GOST 4919.1−77 |
Sec. 2 |
| GOST 20478−75 |
Sec. 2 |
| GOST 22180−76 |
Sec. 2 |
| GOST 25086−87 |
Sec. 5 |
5. Limitation of actions taken by Protocol No. 2−92 of the Interstate Council for standardization, Metrology and certification (ICS 2−93)
6. EDITION with Change No. 1, approved in June 1987 (IUS 11−87)
This standard specifies a gravimetric method for the determination of the amount of rare earth elements (in mass fraction of rare earth elements from 0.3 to 5.0%) and titrimetric method for the determination of cerium (when the mass fraction of cerium is from 0.1 to 1.5%).
The method is based on separation of rare earth elements and cerium from the main mass of magnesium with a solution of sodium tetraborate in the presence of ammonium chloride. The hydrates of the metallic oxides are dissolved in hydrochloric acid and excrete oxalates of rare earth elements.
Definition of finish by the calcination of the oxalate to obtain oxides. If the alloy contains cerium, the precipitate after calcination is dissolved in acid, cerium is oxidized to tetravalent state and titrated with a solution of salt Mora.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 3240.0.
2. REAGENTS AND SOLUTIONS
Hydrochloric acid according to GOST 3118 and diluted 1:1, 1:99.
Sulfuric acid according to GOST 4204, and diluted 1:5.
Ammonia water according to GOST 3760.
Ammonium chloride according to GOST 3773, 25% solution.
Sodium tetraborate according to GOST 4199, 2% solution.
Ammonium neccersarily according to GOST 20478, a 15% solution.
Oxalic acid according to GOST 22180, rich and 3% solutions.
Cerium ferrous sulfate, 0.05 M solution. The titer of the solution set on oxalic acid.
Methyl orange, a 0.2% solution.
Ferroin, preparation and storage according to GOST 4919.1.
Salt of protoxide of iron and ammonium double sulfate according to GOST 4208 (salt Mora) and 0.02 M solution. The titer of the solution set for sulfate and cerium. This 10 cmof a solution of cerium sulfate is placed in a conical flask with a capacity of 250 cm
, is diluted with 40 cm
of water, add 15 cm
of a 15% solution of ammonium naternicola 5 cm
of sulphuric acid diluted 1:5 and boil for 5 minutes Then carefully rotate the bulb and remove oxygen, cool the solution, add two drops of the indicator mixture and titrate with Mohr salt solution until the appearance of pink color.
The titer of a solution of iron sulfate (), expressed in g/cm
of cerium, calculated by the formula
where is the number of cerium taken to install titer, g;
— the volume of iron sulfate solution consumed for titration, sm
.
(Changed edition, Rev. N 1).
3. ANALYSIS
The weight of the portion of the alloy is determined depending on the mass fraction of the sum of rare earth elements, as indicated in the table.1.
Table 1
| Mass fraction of rare earth elements, % |
The weight of the portion of the alloy, g |
| From 0.3 to 4.0 |
1 |
| SV. 4,0 «5,0 |
0,5 |
The sample is placed in a beaker with a capacity of 250 cmadd 30 cm
of hydrochloric acid diluted 1:1, and heated to complete dissolution.
The side of the Cup washed with water, and add 50 cmof a solution of ammonium chloride, neutralized with ammonia solution on methyl orange to yellow in color, pour 10 drops of ammonia in excess, cool, add 100 cm
of a solution of sodium tetraborate was mixed thoroughly with a glass rod and allowed to stand for coagulation of the precipitate. After 40−50 min, the solution was filtered, without mixing, through two medium density filter, transfer the precipitate on a filter and washed 5−6 times with a solution of sodium tetraborate.
The precipitate is dissolved on the filter in 30 cmhot hydrochloric acid, diluted 1:1. The filter is washed several times with hot water, solution is collected in a glass which was dissolved sample was evaporated to near dryness.
The precipitate is dissolved in 50 cmof a hydrochloric acid solution diluted 1:99, add 30 cm
of water, heated to boiling and precipitated rare earth elements is 50 cm
, heated to the boiling point of a saturated solution of oxalic acid, stirring thoroughly for 5 min with a glass rod with a rubber tip.
The solution with the precipitated sludge allowed to stand for 3−4 h, and if the content of rare earth elements is insignificant, until the next day. The precipitate is then collected on a dense filter and washed 10−12 times with cold 3% solution of oxalic acid.
The precipitate is filter-dried, calcined for 1 h at 950 °C, cooled and weighed amount of rare earth elements.
For the determination of cerium, suspended sediment is transferred to a conical flask with a capacity of 250 cm, and heating is dissolved in 20−30 cm
of sulphuric acid (1:5), then the solution was evaporated until the appearance of fumes of sulphuric acid for 1.5 h, poured 10−15 cm
solution naternicola ammonium and boil for 5−7 minutes, Carefully rotating the flask, and remove oxygen and cool the solution, then add 1−2 drops of ferroin and titrated cerium salt solution Mora to obtain a stable pink color.
(Changed edition, Rev. N 1).
4. PROCESSING OF THE RESULTS
4.1. The mass fraction of the sum of rare earth elements (a) percentage calculated by the formula
where — mass of oxides of rare earth elements, g;
0,82 — average conversion rate of oxides of rare earth elements to pure metals; — the weight of the portion of alloy,
4.2. Mass fraction of cerium () in percent is calculated by the formula
where — the volume of sulfate solution of ferrous iron consumed in the titration, cm
;
the titer of a solution of sulphate ferrous iron, expressed in g/cm
cerium;
— the weight of the portion of alloy,
4.3. Allowable absolute discrepancies in the results of parallel measurements of the mass fraction of rare earth elements should not exceed the values given in table.2.
Table 2
| Mass fraction of rare earth elements, % |
The absolute allowable difference, % |
| 0.3 to 0.5 |
0,05 |
| SV. 0,5 «1,5 |
0,1 |
| Is 1,5 5,0 |
0,25 |
4.4. Allowable absolute discrepancies in the results of parallel measurements of the mass fraction of cerium should not exceed the values given in table.3.
Table 3
| The mass fraction of cerium, % |
The absolute allowable difference, % |
| From 0.1 to 0.4 |
0,015 |
| SV. Of 0.4 «to 1.0 |
0,04 |
| «1,0» 1,5 |
0,06 |
5. CONTROL OF MEASUREMENT ACCURACY
Control the accuracy of measuring the mass fraction of cerium is from 0.1 to 1.5% is carried out using the State standard sample GSO 3363.
In addition, use the national standard samples of magnesium alloys, newly issued, as well as industry standard samples and standard samples of the enterprise of magnesium alloys, issued in accordance with GOST 8.315. Accuracy control measurement is carried out in accordance with GOST 25086.
Allowed to control the accuracy of measuring the mass fraction of the sum of rare earth elements and cerium by a method of additives.
Sec. 5. (Added, Rev. N 1).
