GOST 25599.4-83
GOST 25599.4−83 (ST SEV 2951−81) sintered hard Alloys. Method for the determination of cobalt (with Change No. 1)
GOST 25599.4−83
(CT CMEA 2951−81)
Group B59
STATE STANDARD OF THE USSR
SINTERED HARD ALLOYS
Method for the determination of cobalt
Sintered hardmetals. Method for the determination of cobalt
OKP 19 6100
Date of introduction 1984−01−01
Resolution of the USSR State Committee on standards of January 20, 1983 N 291 validity period is set with
_______________
* Expiration removed by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS No. 5/6, 1993). — Note the manufacturer’s database
REPRINTING. August 1984
The Change N 1, approved and introduced with effect from
Change No. 1 made by the manufacturer of the database in the text ICS N 7, 1988
This standard sets the potentiometric method for the determination of cobalt when the mass proportion of 1 to 60% in hard sintered alloy, carbide carbide mixtures.
The method is based on the oxidation of cobalt to the trivalent state genesisintermedia potassium in ammonia environment. Excess zhelezovanadievoj octarepeat potentiometric potassium sulfate solution cobalt.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 14339.0−82.
2. APPARATUS, REAGENTS AND SOLUTIONS
Installation for carrying out potentiometric titration.
The platinum indicator electrode.
The tungsten wire electrode comparison.
Sulfuric acid GOST 4204−77, density 1.84 g/cm.
Ammonia water according to GOST 3760−79, density of 0.91 g/cm.
Ammonium sulfate according to GOST 3769−78, 25% solution.
Ammonium citrate according to GOST 3653−78, 30% solution.
Nitric acid GOST 4461−77, density 1.4 g/cm.
Hydrofluoric acid according to GOST 10484−78, density 1.12 g/cm.
Paper indicator.
Cobalt sulfate or metal.
The sulfate solution cobalt standard 0.002 g/cmprepared in two ways:
a) 10 g of cobalt sulfate dissolved in water, poured 10 cmof sulphuric acid, transferred into a measuring flask with volume capacity of 1000 cm
, is diluted to the mark with water and mix. The concentration of the solution set by electrolytic method;
b) 2.0 g of cobalt metal was dissolved in 10 cmof nitric acid, is evaporated to wet salts, poured 10 cm
of sulphuric acid and evaporated to fumes of sulphuric anhydride. The solution is transferred into a measuring flask with volume capacity of 1000 cm
, is diluted to the mark with water and mix.
Potassium genesisintermedia according to GOST 4206−75, a solution of 0.03 g·EQ/DM.
Zhelezovanadievoj 11 g of potassium is dissolved in water in a volumetric flask with a capacity of 1000 cm, is diluted to the mark with water and mix.
To establish the ratio of the amounts (concentrations) of solutions of cobalt sulphate and potassium relatoseroticos in a glass with a capacity of 400 cmpour 20 cm
of a solution of ammonium sulfate, 10 cm
of a solution of citrate of ammonium, 100−200 cm
of water, 80 cm
of ammonia and 10 to 20 cm
of a solution of potassium relatoseroticos.
The prepared solution is titrated potentiometric sulfate solution cobalt.
The volume ratio (concentration) of solutions () is calculated by the formula
where is the volume of solution of potassium relatoseroticos taken to relate, refer
;
— the volume of cobalt sulfate solution consumed for titration of potassium relatoseroticos, cm
.
The type of analytical scale VLR-200 or any other type providing a weighing error of no more than ±0,0002 g.
Magnetic stirrer MM-5.
(Changed edition, Rev. N 1).
3. ANALYSIS
Based on the estimated cobalt content of take the weight and mass in accordance with table.1, dissolve with heating in 10 cmsulfuric acid and 5 g of ammonium sulfate in a heat proof beaker covered with watch glass, or the weight of the sample moistened with water, dissolved in a mixture of 15−20 cm
hydrofluoric and 5 cm
of nitric acid in a platinum Cup.
Table 1
| Mass fraction of cobalt, % |
The weight of the portion of the sample, g |
The volume of the solution relatoseroticos potassium, see | |||
| From |
1 | to | 5 | 0,5 |
15 |
| SV. |
5 | « | 10 | 0,2 |
15 |
| « | 10 | « | 30 | 0,1 |
20 |
| « | 30 | « | 50 | 0,1 |
30 |
| « | 50 | « | 60 | 0,1 |
35 |
After dissolution of the sample poured 5 cmof a solution of sulphuric acid and evaporated to fumes of sulphuric anhydride. The cooled solution is poured into a Cup, washing Cup 2−3 times potamianou water.
Add in small portions of 20 cmof a solution of ammonium sulfate, 10 cm
of a solution of ammonium citrate and 150 cm
of water. The sample solution is carefully neutralized with ammonia solution until slightly acid reaction on indicator paper «Congo», add 80 cm
of ammonia solution, after which the solution cooled.
To analyze the solution from the burette pour the solution of potassium relatoseroticos in accordance with the table.1.
A solution was prepared by lowered magnetic stirrer and electrodes and octarepeat excess relatoseroticos potassium sulfate solution of cobalt to a sharp jump of potential.
(Changed edition, Rev. N 1).
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of cobalt () in percent is calculated by the formula:
where — volume of the solution relatoseroticos potassium added to the analyzed solution, cm
.
— the volume of cobalt sulfate solution used for back titration of an excess of a solution of potassium relatoseroticos, cm
;
— the ratio of the amounts (concentrations) of solutions of cobalt sulphate and potassium relatoseroticos;
the cobalt concentration in the standard solution of sulfate of cobalt, g/sm
;
— the weight of the portion of the sample,
G.
4.2. Permissible differences between results of parallel measurements at a confidence level =0.95 does not exceed the values specified in table.2.
Table 2
| Mass fraction of cobalt, % |
The allowable divergence, % | ||||
| From | 1,0 | to | 2,5 | 0,05 | |
| SV. | 2,5 | « | 5 | 0,1 | |
| « | 5 | « | 10 | 0,15 | |
| « | 10 | « | 30 | 0,2 | |
| « | 30 | « | 40 | 0,25 | |
| « | 40 | « | 50 | 0,3 | |
| « | 50 | « | 60 | 0,35 | |
