GOST 11930.4-79

• gost-119304-79.pdf (113.88 KiB)
  ГОСТ 11930.4-79

GOST 11930.4−79 Materials surfacing. Method of determining chromium (with Amendments No. 1, 2)

GOST 11930.4−79

Group B09

INTERSTATE STANDARD

MATERIALS SURFACING

Method for the determination of chromium

Hard-facing materials. Method of chromium determination

ISS 25.160.20
AXTU 1709

Date of introduction 1980−07−01

The decision of the State Committee USSR on standards on March 21, 1979 N 982 date of introduction is established 01.07.80

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

REPLACE GOST 11930−66 in part of sec. 2

EDITION (August 2011) with Amendments No. 1, 2 approved in December 1984, December 1989 (IUS 3−85, 3−90)


This standard specifies a volumetric method for the determination of chromium (in mass fraction of chromium from 5 to 88%) in the surfacing materials.

The method is based on oxidation to hexavalent chromium with ammonium persulfate in the presence of silver nitrate as a catalyst. Definition of chrome done by titration of a solution of hexavalent chromium with a solution of salt Mora in the presence of the indicator.

(Changed edition, Rev. N 2).

1. GENERAL REQUIREMENTS

1.1. General requirements for method of analysis according to GOST 11930.0−79.

2. REAGENTS AND SOLUTIONS

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

Ammonium neccersarily according to GOST 20478−75.

Orthophosphoric acid according to GOST 6552−80.

Nitric acid GOST 4461−77.

Sodium peroxide.

Sodium chloride according to GOST 4233−77.

Sodium carbonate according to GOST 84−76, a solution with a mass fraction of 0.2%.

Silver nitrate according to GOST 1277−75, a solution with a mass fraction of 0.5%.

Salt of protoxide of iron and ammonium double sulfate (salt Mora) according to GOST 4208−72, 0.1 N. solution. The titre of the salt solution Mora set to 0.1 n solution of potassium dichromate.

Potassium dichromate, 0.1 N. solution; prepared from fixanal.

Phenylantranilic acid solution with a mass fraction of 0.2%; prepared by dissolving in a solution with a mass fraction of 0.2% of sodium carbonate.

(Changed edition, Rev. N 2).

3. ANALYSIS

3.1. Chromium in the alloys not containing vanadium determined in the filtrate obtained after the determination of silicon GOST 11930.3−79.

Of volumetric flasks with a capacity of 200 cmis taken 50 cmof the analyzed solution in a conical flask with a capacity of 250−300 cm, flow 15 cmof sulphuric acid, diluted 1:4, and 2 cmof phosphoric acid. For the oxidation of chromium is administered 2 cmof solution with a mass fraction of 0.5% silver nitrate, 1 to 2 g of ammonium persulfate.

The solution in the flask is diluted with water to 150 cmand boil for approximately 10 min.

For materials containing manganese, is added 1 g of ammonium persulfate if the solution is not painted in crimson color, and re-boil for 5−10 min. Then the flask is removed from the tiles, add 1−2 g of sodium chloride until the color of the solution yellow and again boil for 5 min to remove chlorine. After cooling the solution chrome titrated with a solution of salt Mora in the presence of 0.5 cmof solution with a mass fraction of 0.2% phenylanthranilic acid before transition of colouring from crimson to green.

3.2. To mix brands of powders for surfacing and chromium boride sample weighing 0.1 g was dissolved in 50 cmof sulphuric acid, diluted 1:4, pour 2 cmof nitric acid and evaporated twice to a weak solution of sulphuric acid fumes. If the linkage does not dissolve completely, the solution was filtered (the filtrate save) and domplast undissolved part of the sample with carbonate of sodium at 900−950 °C. the Melt leached with water, acidified with sulphuric acid, and attach to the filtrate. The solution is poured into a measuring flask with a capacity of 200 cm, is diluted to the mark with water and mix.

For determining chromium taken 50 cmof the analyzed solution in a conical flask with a capacity of 250−300 cmand pour 3 cmof sulfuric acid, 2cmof phosphoric acid, dilute with water to 150 cm, are 2 cmof solution with a mass fraction of 0.5% of silver nitrate, 2−3 g naternicola ammonium and boil until its destruction. The cooled solution was titrated as described in section 3.1.

3.1, 3.2. (Changed edition, Rev. N 2).

3.3. For chromium carbide sample weight of 0.1 g iron alloy, Nickel or a glassy carbon crucible with 5−8 g of a mixture of sodium carbonate peroxide and sodium (1:2) at 600−650 °C for 15 min. After cooling, the melt leached with water and transferred to a volumetric flask with a capacity of 200 cm. For the determination of chromium part of the solution was filtered into a dry beaker. Take 50 cmof the analyzed solution, neutralized with sulfuric acid and poured 5 cmof concentrated sulfuric acid. The solution was evaporated to sulphuric acid fumes, pour 2 cmof phosphoric acid, dilute with water to 120−150 cmand further analysis are as indicated in claim 3.1.

(Changed edition, Rev. N 1).

4. PROCESSING OF THE RESULTS

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

,

where  — the amount of salt Mora, used for titration of chromium, cm;

mass concentration of salt solution Mora, expressed in g/cmchrome;

 — the volume of the analyzed solution, cm;

 — aliquota part of the analyzed solution, cm;

 — the weight of the portion,

4.2. The difference between the largest and smallest results of the three parallel measurements, and the two results of the analysis at a confidence level of 0.95 does not exceed the permissible differences given in the table.

4.1, 4.2. (Changed edition, Rev. N 2).