GOST 2604.7-84

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  ГОСТ 2604.7-84

GOST 2604.7−84 alloy Cast iron. Methods for determination of vanadium (Change No. 1)

GOST 2604.7−84

Group B09

INTERSTATE STANDARD

ALLOY CAST IRON

Methods for determination of vanadium

Alloy cast iron. Methods for determination of vanadium

ISS 77.080.10
AXTU 0809

Date of reference 1985−01−01

The decision of the State Committee of USSR on standards as of January 27, 1984 N 358 date of introduction is established 01.01.85

Limitation of actions taken by Protocol No. 4−93 of the Interstate Council for standardization, Metrology and certification (ICS 4−94)

REPLACE GOST 2604.7−77

EDITION with Change No. 1, approved in April 1989 (IUS 7−89).


This standard specifies the method of amperometric titration of vanadium (at the mass fraction of vanadium from 0.02 to 0.20%) and titrimetric method (with mass fraction of vanadium of 0.05 to 1.0%) in the doped iron.

The standard corresponds to the international standard ISO 4947−86 in part by potentiometric method.

(Changed edition, Rev. N 1).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 28473−90.

1.2. The error analysis result (at p = 0.95) must not exceed the limit given in the table under the following conditions:

the discrepancy between the results of two (three) parallel dimensions should not exceed (at p = 0.95) of the values given in the table;

played in the standard sample, the value of the mass fraction of the element must not vary from certified more than acceptable (at p = 0.95) value given in the table.

If any of the above conditions, a second measurement of the mass fraction of vanadium. If in repeated measurements the precision requirement of the results are not met, the results of the analysis recognize the incorrect measurements cease to identify and eliminate the causes of violation of the normal course of analysis.

The divergence of the two middle results of an analysis performed under different conditions (for example, when the control intralaboratory reproducibility) shall not exceed (at p = 0.95) of the values given in the table.

(Added, Rev. N 1).

2. DEFINITION OF VANADIUM BY THE METHOD OF AMPEROMETRIC TITRATION

2.1. The essence of the method — according to GOST 12351−2003.

2.2. Apparatus, reagents and solutions — according to GOST 12351−2003 with additions.

Sulfuric acid GOST 4204−77 and diluted 1:1, 1:2, 1:4, 1:10.

Standard solutions of vanadium pentoxide.

A solution with A mass concentration of vanadium of 0.001 g/cm: 1,7852 g of vanadium pentoxide was dissolved with heating in 50 cmof sulphuric acid (1:2), add 5 cmof nitric acid, boil the solution to remove the oxides of nitrogen and evaporated to release vapors of sulfuric acid. The contents of the Cup is cooled, washed wall with water and again evaporated to release vapors of sulfuric acid. After cooling, add 100 cmof water and dissolved salts when heated. The solution was cooled, transferred to a measuring flask with volume capacity of 1000 cm, made up to the mark with sulphuric acid (1:10) and stirred.

Solution B with a mass concentration of vanadium 0.0001 g/cm: 100 cmstandard solution And placed in a measuring flask with volume capacity of 1000 cm, made up to the mark with sulphuric acid (1:10) and stirred

T.

2.3. Analysis — according to GOST 12351−2003 with the Supplement.

If upon dissolution of the sample remained insoluble residue containing silicic acid and carbon, it was filtered on the filter «white ribbon» and washed 5−6 times with hot water collecting the filtrate and washings in a beaker with a capacity of 400 cm. The filter with precipitate was placed in a platinum crucible, dried, incinerated, and calcined. The residue in the crucible is moistened with 2−3 drops of water, add 3−4 drops of sulfuric acid, 3−4 cmhydrofluoric acid and cautiously evaporated to remove vapors of sulfuric acid. The crucible is calcined at a temperature of 550−600 °C, cooled, the residue in the crucible is fused with a 2−3 g peacemaking potassium. The crucible is cooled, the melt is dissolved by heating to 30−40 cmwater in a beaker with a capacity of 250 cm. The resulting solution was attached to the filtrate.

2.2, 2.3. (Changed edition, Rev. N 1).

3. TITRIMETRIC METHOD

3.1.The essence of the method

The method is based on the oxidation of vanadium (IV) with potassium permanganate in sulfuric acid medium with amperometric, potentiometric or visual indication of the endpoint of the titration of vanadium (V) with a solution of double sulphate salts of ferrous iron and ammonium.

Chrome for the mass concentration above 3.5% is removed by Stripping chloride gromila.

3.2. Apparatus, reagents and solutions

Any installer for amperometric or potentiometric titration of vanadium, which provides the necessary accuracy.

Hydrofluoric acid according to GOST 10484−78.

Potassium preservatory according to GOST 7172−76.

Sodium carbonate according to GOST 83−79, a solution of 0.002 g/cm.

Acid phenylantranilic, indicator: 0.2 g phenylanthranilic acid are dissolved in 100 cmof hot sodium carbonate solution, cool.

Other reagents, solutions and their preparation is according to claim 2.2

3.3. Analysis

A portion of the cast iron mass of 1 g and for the mass concentration of vanadium from 0.05 to 0.5% or 0.5 g — at a mass share of vanadium, 0.5 to 1.0% is placed in a beaker with a capacity of 400 cm, and depending on the chemical composition of cast iron is dissolved.

3.3.1. For the mass concentration of chromium up to 3.5% of the sample is dissolved in 50 cmof sulphuric acid (1:4) with moderate heat, carefully added dropwise nitric acid until the termination of foaming and the excess of 3−5 cm. Heated to remove oxides of nitrogen and evaporated to release vapors of sulfuric acid. If the suspension does not dissolve in sulphuric acid (1:4), it is dissolved in 30−40 cmof hydrochloric acid when heated, carefully add drops of nitric acid until the termination of foaming and the excess of 3−5 cm. Heated to remove oxides of nitrogen. The solution was cooled, poured 50 cmof sulphuric acid (1:4) and evaporated to release vapors of sulfuric acid. After cooling, pour the 100 cmof water and dissolved salts when heated.

3.2 to 3.3.1. (Changed edition, Rev. N 1).

3.3.1.1. If upon dissolution of the sample remained insoluble residue containing silicic acid and carbon, it was filtered on the filter «white ribbon» and washed 5−6 times with hot water collecting the filtrate and washings in a beaker with a capacity of 400 cm. The filter with precipitate was placed in a platinum crucible, dried, incinerated, and calcined. The residue in the crucible is moistened with 2−3 drops of water, add 3−4 drops of sulfuric acid, 3−4 cmhydrofluoric acid and cautiously evaporated to remove vapors of sulfuric acid. The crucible is calcined at a temperature of 550−600 °C, cooled, the residue in the crucible is fused with a 2−3 g peacemaking potassium. The crucible is cooled, the melt is dissolved by heating to 30−40 cmwater in a beaker with a capacity of 250 cm. The resulting solution was attached to the filtrate.

3.3.2. When the mass fraction of chromium in excess of 3.5% of the sample was dissolved in 20−30 cmof hydrochloric acid when heated, pour 10−15 cmof nitric acid and continue the heating until complete dissolution of the sample. Then pour 40−50 cmof perchloric acid, the solution is heated to oxidation of chromium chloride and distilled chromyl as specified in claim 2.3.

The solution is twice evaporated to highlight the dense fumes of perchloric acid, washing the side of the Cup with water, pour 50 cmof sulphuric acid (1:4) and cooled.

To the solution obtained by any of the methods described in the PP.3.3.1 and 3.3.2, poured 10 cmof a solution of iron (II) sulphate for the recovery of partially oxidized chromium. The solutions were cooled to 20 °C, with constant stirring, added dropwise a solution of potassium permanganate 25 g/DMuntil a stable pink color. After 1−2 min added dropwise a solution of azotistykh sodium 0.02 g/cmto the disappearance of the pink coloration immediately, and 10 cmof the urea solution. After 3 min the solution was titrated with a solution of salt Mora, fixing the end point of a potentiometric titration or amperometric method.

When the visual fixation of the titration end point to the solution prepared for titration, add 10 cmof phosphoric acid, 80 cmof sulphuric acid (1:1), cooled, add 5−6 drops phenylanthranilic acid and titrated it with a solution of salt Mora before moving cherry color of the solution yellow-green.

(Changed edition, Rev. N 1).

4. PROCESSING OF THE RESULTS

4.1. Mass fraction of vanadium () in percent is calculated by the formula

,

where  — the volume of salt solution Mora, used for titration, cm;

mass concentration of salt solution Mora on vanadium, g/cm;

the weight of cast iron,

4.2. Norms of accuracy and norms of accuracy control of determination of mass fraction of vanadium given in the table.

4.1, 4.2. (Changed edition, Rev. N 1).