GOST 12645.7-77

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  ГОСТ 12645.7-77

GOST 12645.7−77 indium. Method for the determination of zinc (with Amendments No. 1, 2, 3)

GOST 12645.7−77

Group B59

STATE STANDARD OF THE USSR

INDIUM

Method of determining zinc

Indium. Method for determination of zinc

AXTU 1709

Date of introduction 1978−07−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of nonferrous metallurgy of the USSR

DEVELOPERS

A. P. Sychev, L. K. Larin, M. G. Sun (leader); V. N. Makarceva; N. With. References:; E. V. Lisitsyn, N. Romanenko, V. A. Kolesnikov

2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 08.07.77 N 1715

Change No. 3 adopted by the Interstate Council for standardization, Metrology and certification 15.03.94 (report of the Technical Secretariat N 1)

The adoption voted:

3. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

4. Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 5−6-93)

5. REVISED (March 1998) with Amendments No. 1, 2, 3, approved in February 1983, December 1987-June 1996 (IUS 5−83, 3−88, 9−96)


This standard sets the polarographic method for determining zinc in India with a mass fraction of zinc from 1·10to 5·10%.

The method is based on the separation of indium extraction with diethyl ether from a solution bromatological acid (HBR)=5 mol/DM. Polarographically zinc carried out on the background ammonia and ammonium chloride.

The half-wave potential of zinc is equal to minus 1.36 relative to the saturated calomel electrode.

(Changed edition, Rev. N 1, 2).

1. GENERAL REQUIREMENTS

1.1. General requirements for method of analysis and security requirements — according to GOST and GOST 12645.0 22306.

(Changed edition, Rev. N 2).

2. APPARATUS, REAGENTS AND SOLUTIONS

Polarograph oscilloscope or AC, allowing to determine 0.1 mg/DMand above of zinc, equipped with an electrolyzer with a capacity of 3−5 cm.

Bromatologia acid according to GOST 2062, purified by double distillation in a quartz device solutions (NVG)=6,5−7 mol/DMand (NVH)=5 mol/DM.

The concentration of distilled bromatological acid set by titration with solution of potassium hydroxide or sodium hydroxide.

Quartz ware according to GOST 19908.

Hydrochloric acid according to GOST 14261 or obtained by saturation with hydrogen chloride double-distilled water, diluted 1:3 and 1:20.

The acid chloride.

Distilled water according to GOST 6709, double-distilled in quartz apparatus.

Diethyl ether (medical).

Ammonia water according to GOST 24147.

Ammonium chloride according to GOST 3773.

A background electrolyte consisting of 20 cmof ammonia, 20 g of ammonium chloride and 180 cmof water.

Sanitarily sodium (sodium sulfite) the crystal according to GOST 195.

Zinc metal granulated.

Standard solutions of zinc.

Solution A, prepared as follows: 0,100 g of zinc metal is dissolved in the quartz glass in 5−10 cmof hydrochloric acid diluted 1:3, the solution was evaporated to obtain a wet salts. Poured 30 cmof hydrochloric acid, heated, cooled, quantitatively transferred to a volumetric flask with a capacity of 1 DM, bring to mark and mix.

1 cmof solution A contains 0.1 mg of zinc.

Solution B is prepared as follows: 10 cmstandard solution And transferred to a volumetric flask with a capacity of 100 cm, poured 5cmof hydrochloric acid, cooled and adjusted to the mark with water.

1 cmof a solution contains 0.01 mg of zinc.

Solution; prepared as follows: 10 cmof solution B is placed in a volumetric flask with a capacity of 100 cm, poured 5cmof hydrochloric acid, cooled and adjusted to the mark with water.

1 cmof the solution contains 0.001 mg of zinc.

The calibration solutions. Three batches India at 2,000−5,000 g, depending on the zinc content in the sample, are added (accurately measured) the volume of the calibration solution B or C, which give the zinc concentration in the calibration solutions, the respective concentrations of zinc in the test solutions.

Sample India dissolved in 10−20 cmsolution bromatological acid (HBR)=6,5−7 mol/DMand further analysis are as shown below.

(Changed edition, Rev. N 2, 3).

3. ANALYSIS

The weight India weight of 2,000−5,000 g (depending on the zinc content) was placed in a quartz flask with a capacity of 50−100 cm, 10−20 cm pour thesolution bromatological acid (HBR)=6,5−7 mol/DM, cover the flask with a watch glass and dissolve the poorly heated hot plate until complete dissolution of the metal.

After dissolution of the sample hour glass is washed with a small amount of water and evaporated the solution to dryness. The residue is dissolved in 5−10 cmof the solution bromatological acid (HBR)=5 mol/DMand cooled. The solution was quantitatively decanted into a quartz separating funnel, wash the walls twice with portions of 1 cmof solution bromatological acid (HBR)=5 mol/DM, add the same amount of diethyl ether and shaken for 1−1,5 min. After settling, the aqueous phase is drained into another separating funnel and repeat the extraction twice India the same amount of air.

The aqueous layer transferred to a clean quartz flask and remove the remains of the ether on a water bath, and then evaporated to dryness.

To the dry residue add a few drops of perchloric acid and gently evaporated to dryness. The rest should be white, otherwise the processing of perchloric acid repeat.

The residue is moistened with 2−3 drops of hydrochloric acid diluted 1:20 and, depending on the zinc content in the sample, pour the precisely measured 5−25 cm,background electrolyte, add about 0.1 g of sodium sulfite, poured into the cell and polarographic solution when the polarization voltage from minus 1.1 to minus 1.5 V. the peak Potential of zinc minus 1.36 relative to the saturated calomel electrode.

At the same time through all stages of the analysis, spend 2−3 reference experiment for inclusion in the analysis result of the relevant amendment.

(Changed edition, Rev. N 1, 2, 3).

4. PROCESSING OF THE RESULTS

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

,

where is the height of the peak of a wave of zinc, obtained by polarography of the test sample solution minus reference experiment, mm.

 — volume of test solution, cm;

 — the weight of the portion of the sample corresponding to aliquote part g;

 — the ratio of the wave height obtained in polarography of the calibration solution mass concentration of this solution, mm·DM/mg, calculated by the formula

,

where the wave height of zinc in the calibration solution minus the height of the waves of the zinc solution in the reference experiment, mm.

 — mass concentration of zinc in calibration solution, mg/DM.

(Changed edition, Rev. N 3).

4.2. For the results analysis be the arithmetic mean of results of three parallel measurements.

The difference between the largest and smallest of the three results of parallel measurements with a confidence level =0.95 does not exceed the values of permissible differences of the three results of parallel measurements calculated by the formulae:

for a mass fraction of zinc from 1·10to 2·10%;

for a mass fraction of zinc from 2·10to 5·10%,

where is the arithmetic mean of results of three parallel measurements.

The difference between the smaller and larger of the two results of the analysis of the same samples with a confidence level =0.95 does not exceed the values of permissible differences of the two analysis results calculated by the formulae:

for a mass fraction of zinc from 1·10to 2·10%;

for a mass fraction of zinc from 2·10to 5·10%,

where  — the average of the two matched analyses.

(Changed edition, Rev. N 2).