GOST 21877.7-76

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  ГОСТ 21877.7-76

GOST 21877.7−76 Babbit tin and lead. Method for the determination of arsenic (with Amendments No. 1, 2)

GOST 21877.7−76

Group B59

STATE STANDARD OF THE USSR

BABBIT TIN AND LEAD

Method for the determination of arsenic

Tin and lead babbits. Method for the determination of arsenic*

AXTU 1709**
__________________
* The name of the standard. Changed the wording, Rev. N 2.
** Added, Rev. N 2.

Valid from 01.01.78
to 01.01.83*
_______________________________
* Expiration removed
according to the Protocol of the Intergovernmental Council
for standardization, Metrology and certification
(IUS N 2, 1993). — Note the manufacturer’s database.

DEVELOPED by the Central research Institute for tin industry (Tsniiolovo)

Director V. A. Arsenico

Supervisor S. V. Meshkov

Executor G. V. Ivanova

INTRODUCED by the Ministry of nonferrous metallurgy of the USSR

Zam. Minister N.N. Chepelenko

The draft all-Union scientific research Institute of standardization (VNIIS)

Director A. V. Gichev

APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from may 24, 1976 N 1264

REPLACE GOST 1380.9−70

MADE: the Change in N 1, approved and put into effect by the Decree of the USSR State Committee for standards from 14.02.83 N 805 01.07.83 c, Change in N 2, approved and put into effect by the Decree of the USSR State Committee for standards from 25.06.87 N 2463 with 01.03.88

Change N 1, 2 made by the manufacturer of the database in the text N 6 ICS 1983 ICS N 10 1987


This standard applies to tin and lead babbits and sets the volumetric method for determination of arsenic (arsenic content of from 0.01 to 1%).

The method is based on dissolving the sample Babbitt in sulfuric acid, the recovery of arsenic to the elementary gipofosfata sodium chloride solution, filtered arsenic oxidation with potassium dichromate and back titration of the excess cast-Maura salt by potassium dichromate in the presence phenylanthranilic acid as indicator.

1. GENERAL REQUIREMENTS

1.1. General requirements for method of analysis according to GOST 21877.0−76.

2. REAGENTS AND SOLUTIONS

Sulfuric acid GOST 4204−77, GOST and diluted 1:9.

Hydrochloric acid by the GOST 3118−77 and diluted 1:1 and 1:3.

Sodium posterolaterally (hipofosfit sodium) according to GOST 200−76; solution prepared by dissolving 300 g of salt in 1 litre of hydrochloric acid diluted 1:1. The solution is prepared the day of application.

Ammonium chloride according to GOST 3773−72, a solution of 50 g/DM.

Sodium bicarbonate according to GOST 4201−79.

Orthophosphoric acid according to GOST 6552−80.

A mixture of acids: 150 cmof concentrated sulfuric acid poured to 500 cmof water, cooled, poured 150 cmof phosphoric acid and add water to 1 L.

Iron carbonyl.

Salt Mora (double sulphate salt of protoxide of iron and ammonium) according to GOST 4208−72, a solution concentration of 0.02 mol/l; prepared by dissolving 38.5 g of salt Mora in 5 l of water containing 250 cmof concentrated sulfuric acid.

Diphenylamine according to GOST 5825−70, solution; is prepared as follows: 1 g of diphenylamine moistened with 3−5 cmof water and dissolved in 100 cmof concentrated sulfuric acid with stirring.

Phenylantranilic acid solution; prepared as follows: 0.1 g sodium bicarbonate are dissolved in 20−40 cmof distilled water, add 0.1 g phenylanthranilic acid, is heated, not boiling, cooled and diluted with water to 100 cm.

Potassium dichromate according to GOST 4220−75, solution of molar concentration of 0.003 mol/l; prepared by dissolving 4,908 g of potassium dichromate in 5 l of water.

The washing liquid: to 100 cmof hydrochloric acid diluted 1:3, add 1 g of sodium hypophosphite.

The installation of the titer of a solution of potassium dichromate.

3−4 flasks with a capacity of 250 cmwith Bunsen valves and placed on a 0.050 g of pure metallic iron, 0.5 g of sodium bicarbonate and dissolved in 40−50 cmof sulphuric acid, diluted 1:9. After dissolution of iron, the solution is slightly heated and cooled, without removing the tube. The solution was then quickly diluted with water to 200 cm, 25 cm pour themixture of acids, two drops of diphenylamine solution and titrated solution of potassium dichromate until a stable blue-violet staining solution.

The molar concentration of potassium dichromate (mol/DM) is calculated according to the formula

,

where  — the weight of the portion of metallic iron equal to 0.05 g;

 — the volume of potassium dichromate solution consumed for titration, cm;

is the molar concentration of potassium dichromate, in mol/DM;

is the molar equivalent weight of iron equal 55,85 g/mol.

The mass concentration of the solution () of potassium dichromate for arsenic (g/cm) is calculated according to the formula

,

where is the molar concentration of potassium dichromate;

 — amount of arsenic, corresponding to 1 cmof potassium dichromate solution of a concentration of 0.17 mol/DM.

(Changed edition, Rev. N 1, 2).

3. ANALYSIS

A portion of the babbit with a mass of 0.5 g (arsenic content of from 0.5 to 1%), 1.0 g (arsenic content of from 0.1 to 0.5%) and 3.0 g (arsenic content of up to 0.1%) is placed in a conical flask with a capacity of 250 cm, flow 20 cmof concentrated sulfuric acid, cover the flask with a small funnel or watch glass and heated until complete dissolution of the alloy and whitening of the sludge. The solution was then cooled, poured 50 cmof water and mix thoroughly. In the analysis of babbit brand BS6 precipitate of sulphate of lead to defend for 10−15 minutes and filtered through a filter of medium density in a flask with a capacity of 250 cm. The filter cake was washed 4−5 times with cold water so that the volume of filtrate and wash water did not exceed 70−80 cm.

To the filtrate flow filtrate equal volume of concentrated hydrochloric acid, 20 cmof a solution of sodium hypophosphite, close flask with reflux condenser and heated to boiling. Weak boiling solution is maintained for 30 minutes, then leave the solution on a warm plate to coagulation of the precipitate. Solution and the precipitate was cooled in running water and filtered off the precipitate through a pad of filtrowanie mass, washing the flask and the precipitate is 5−6 times the flushing fluid and then 8−10 times 5%-s ' solution of ammonium chloride.

The precipitate of arsenic with filtrowanie mass quantitatively transferred to a flask, where he conducted the deposition, pour 50 cmof sulphuric acid, diluted 1:9, and dissolved with vigorous shaking in an excess of potassium dichromate, priliva it from a burette 10, 15, or 30 cm(depending on the arsenic content). After dissolution of the arsenic from the burette pour the salt solution Mora to the disappearance of the yellow colour of potassium dichromate and excess (enough to tide 20−30 cm). Next, add 3−4 drops of the solution phenylanthranilic acid and titrate the excess of Mohr salt is 0.02 n solution of potassium dichromate until the appearance of pink colouration of the solution.

(Changed edition, Rev. N

1).

3.2*. When analyzing brands of babbit B83, B88, weighed weight 3.0 g (arsenic content of up to 0.5%) was placed in a conical flask with a capacity of 250 cm, flow 40 cmof concentrated hydrochloric acid, add dropwise a solution of hydrogen peroxide, avoiding the lack of oxidizer. After dissolution, the sample solution is boiled to remove excess of hydrogen peroxide. The cooled solution was poured 70−80 cmof a hydrochloric acid solution, diluted 1:1, add 2−3 g of hypophosphite sodium or calcium. The solution was stirred, closed flask with reflux condenser. Further analysis is carried out as specified in clause 3.1.
____________
* Numbering corresponds to a Change in N 2. — Note the manufacturer’s database.

(Added, Rev. N 2).

4. PROCESSING OF THE RESULTS

4.1. The contents of arsenic () in percent is calculated by the formula

,

where is the total volume of the solution of potassium dichromate consumed for the dissolution of arsenic and titrate the excess of Mohr salt, cm;

 — the volume of potassium dichromate solution consumed for titration of the same amount of salt Mora, which was added to the analyzed solution, cm.

Note. The amount of potassium dichromate consumed for titration of the salt solution Mora, set as follows: the burette is poured into a flask with a capacity of 250 cmsame amount of salt Mora, which was added to the sample solution (20 or 30 cm), pour 50 cmof sulphuric acid, diluted 1:9, 3−4 drops of solution phenylanthranilic acid and titrated with a solution of potassium dichromate until the appearance of pink colouration of the solution;

 — mass concentration of a solution of potassium dichromate for arsenic, g/cm;

 — the weight of the portion of the sample,

(Changed edition, Rev. N 1, 2).

4.2. Allowable absolute differences the results of the analysis shall not exceed the values given in the table.