GOST 13637.7-93

• gost-136377-93.pdf (290.78 KiB)
  ГОСТ 13637.7-93

GOST 13637.7−93 Gallium. Method for the determination of sulfur

GOST 13637.7−93

Group B59

INTERSTATE STANDARD

GALLIUM

Method for the determination of sulfur

Gallium.
Method for the determination of sulphur

AXTU 1709

Date of introduction 1995−01−01

Preface

1. DEVELOPED by the Interstate technical Committee 104 «of the Semiconductor and rare metals products. Especially pure metals», State Institute of rare metals (Giredmet)

INTRODUCED by Gosstandart of Russia

2. ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 4−93 of 19 October 1993)

The adoption voted:

3. Resolution of the Committee of the Russian Federation for standardization, Metrology and certification from 02.06.94 N 160 inter-state standard GOST 13637.7−93 introduced directly as state standard of the Russian Federation from 01.01.95

4. REPLACE GOST 13637.7−77

INFORMATION DATA

REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard specifies the method of alternating-current polarography for the determination of sulfur in Gaul (at the mass fraction of sulfur from 5·10to 1·10%).

The method is based on release of hydrogen sulfide upon dissolution of samples of gallium in a reducing mixture of hydrochloric and itestosterone acids with hypophosphite sodium, trapping hydrogen sulfide polarographic background — a solution of hydroxylamine hydrochloride and ethylenediaminetetraacetic acid in a solution of potassium hydroxide and polarographic determination of sulfur in the form of the sulfide ion on the alternating-current polarography.

1. GENERAL REQUIREMENTS

General requirements for methods of analysis and security requirements — according to GOST 13637.0.

2. APPARATUS, REAGENTS AND SOLUTIONS

Polarograph PPT-1 or PU-1 with mercury dripping electrode and electrolytic cell polarography with the outer anode compartment.

Laboratory scales of the 1st class according to GOST 24104*.
_______________
* On the territory of the Russian Federation GOST 24104−2001. — Note the manufacturer’s database.

A flask with a reflux condenser made of quartz glass or molybdenum for the preparation of a restorative mix with a capacity of 2 DMwith welded tube for purging the solution with argon or nitrogen.

Plant for recovery of sulfur and Stripping of hydrogen sulfide (see drawing) consists of a flask 2 with a capacity of 500±50 cmwith a reflux condenser 5 length (25±5) cm To the outer side of the output tube with a length of (20±5) cm and an orifice diameter of (2±1) mm reverse refrigerator welded spiral quartz nozzle. Receiver 4 for absorption of hydrogen sulfide is a vial with a capacity of (40±5) cm. The gap between the quartz nozzle and the tube walls (1±1) mm. of Argon or nitrogen used as the carrier gas, purified by passing through bubblers 6−8 with a capacity of (150±50) cm, the diameter of the flask (30±5) mm, filled with an alkaline solution of pyrogallol 6, 7 and 8 with distilled water.

1 — hot plate, 2 — the reaction vessel with a reducing compound, 3 — sections, 4 receiver
with an alkaline solution of hydroxylamine, and EDTA (spiral quartz nozzle,
welded to the outer side of the output tube back of fridge)
5 — reverse refrigerator, 6−7 — bubblers with a solution of pyrogallol 250 g/DM
in a solution of potassium hydroxide 250 g/DM, 8 — bubbler with distilled water

Tile laboratory electric power of 400 watts.

Buchner funnel, diameter 80 mm.

Bunsen flask with a capacity of 500 cm.

Pipettes with volume capacity of 0.1; 0.2; 1 and 10 cm.

Volumetric flasks with a capacity of 50; 100; 200 and 1000 cm.

Cylinder measuring capacity 10; 25 cm.

Congo red indicator.

Argon gas according to GOST 10157 or nitrogen gas according to GOST 9293.

Rods graphite OS.h. — 7−3.

Mercury brands r0 according to GOST 4658.

Hydrochloric acid of high purity according to GOST 14261.

Copper dichloride 2-water according to GOST 4167.

Tin dichloride 2-water.

Sulfuric acid according to GOST 4204 solution concentration of 0.05 mol/DM, prepare fiksanala.

Pyrogallol A.

Potassium hydroxide according to GOST 24363.

Hydroxylamine hydrochloride according to GOST 5456.

Potassium chloride according to GOST 4234, OS.h. a saturated solution.

Sodium posterolaterally (hipofosfit sodium) 1-water according to GOST 200.

Sodium sulfide (sodium sulfide) 9-water according to GOST 2053.

Salt is the disodium Ethylenediamine — , , , -tetraoxane acid, 2-water (Trilon B), h. d. a. according to GOST 10652.

Aqueous ammonia high purity GOST 24147.

Solution a: 56 g Cali hydroxide and 50 g Trilon B dissolved in distilled water, the solution was transferred to volumetric flask with a capacity of 500 cm, the volume was adjusted solution to the mark with water and mix. The solution is prepared 2 days before use.

Solution B: to 34.7 g of hydroxylamine hydrochloride dissolved in distilled water, the solution was transferred to volumetric flask with a capacity of 250 cm, the volume was adjusted solution to the mark with water and mix.

Polarographic background, is prepared as follows: 80 cmof solution A, 20 cmof solution B and 150 CCof freshly prepared distilled water mixed the day of use.

Recovery blend: a mixture of 300 cmof concentrated hydrochloric, 500 cmitestosterone acids, 150 g of hypophosphite of sodium and 200 cmof distilled water, boiled for 6−8 hours in the unit with a reflux condenser with constant purging of argon or nitrogen at a speed of 3−4 bubbles per second. During cooling from the recovery of the mixture should stand out of the salt (lack of salts indicates the lack of concentration of hydrochloric acid). Recovery drained mixture with salt and store in a flask with a glass stopper in the dark place.

Distilled water according to GOST 6709.

Sulfur sulfate stock solution: (6,25±0,05) cmof sulfuric acid solution, prepared of fiksanala, diluted with distilled water to 100 cmin a volumetric flask.

1 cmof the solution contains 100 micrograms of sulfate sulfur.

Sulfur sulfate working solution: 10 cmbasic solution of sulphate sulphur is placed in a volumetric flask with a capacity of 100 cmand made up to mark with distilled water.

1 seethe working solution of sulphate sulphur contains 10 µg of sulfur.

Sulfur sulfide stock solution was prepared immediately before use: 20 mg of the dried filter paper sodium sulfide, 1 mg of which is contained of 0.133 mg of sulfur, placed in a volumetric flask with a capacity of 100 cm, flow 20 cmpolarographic background, top up with distilled water to the mark and mix.

1 seethe basic solution of sulfide sulfur contains sulfur of 26.6 µg.

Sulfur sulfide, the working solution is prepared immediately before use: 18.7 cmbasic solution of sulfide sulfur is placed in a volumetric flask with a capacity of 50 cmand bring to mark polarographic background. Stock solution was measured with a burette with an error of ±0.05 cm.

1 seethe working solution of sulfide sulfur contains 10 µg of sulfur.

3. PREPARATION FOR ASSAY

3.1. Check the correct operation of the installation

Assemble setup (see drawing): bubblers 6 and 7 is poured a solution of pyrogallol in caustic potash. To the bubbling chamber 8 is filled with distilled water and connect it with the reaction flask 2 using the vinyl chloride hose. The other connection is carried out using rubber hoses. In the reaction flask is poured 2 150 cmpre-prepared replacement mixture (see sect.2), 1 cmof a solution of chloride of copper concentration of 0.1 mol/DMand 0.1 g of tin dichloride. Through refrigerator 5 pass cold water. Socket of the refrigerator and the socket tube 3 is rubbed with the graphite rod. Through the installation flow, the flow of nitrogen or argon at a speed of 15−25 bubbles in the receiver for 10 seconds On the tightness of the installation is judged by matching the speed of passage of bubbles of argon bubbler 6 and the receiver 4. Correctness of installation check a recovery of a standard solution of sulphate sulphur. For this restoration the mixture is boiled for 1 h for further purification from sulfur. The recovery mixture was cooled, then, in the receiver 4 pour 10 cmof the polarographic background, and a thin section of the refrigerator in the reaction flask 2 are administered 0.2 cmworking solution of sulphate sulphur. The sulfide was removed within 30 min from the moment of boiling of solution. Then the solution from the receiver poured into the electrolytic cell with an external anode (anode compartment pre-filled with mercury at 2 mm above the level of platinum contact and with saturated solution of potassium chloride to the brim and closed with a stopper) and remove polarogram.

Mode polarographically for PU-1: amplitude 10 mV, sweep rate of 3 mV/s, forced open; the initial potential minus the 0.45 V, the peak potential of sulfide ion is approximately minus 0.8 V relative to the saturated calomel electrode.

Due to diffusion of sulfide ions in the anode compartment of the electrolytic potential of the peak may gradually move in a positive direction. So everyday you need to recharge the anode compartment of a cell a fresh saturated solution of potassium chloride. The peak height of sulfur measured vertically, is drawn through the top of the peak to the intersection with a tangent connecting the bases of the branches peak.

The height of the peak on polarogram solution in the receiver is compared with the height of the peak solution of 2 µg of sulfide sulfur in 10 cmsolution (to obtain this solution, 0.2 cmworking solution of sulfide sulfur was diluted in a narrow graduated cylinder polarographic background up to 10 cm). The difference of the heights of both peaks shall not exceed 10% relative to the height of the peak of the working solution of sulfide sulfur. If the difference is larger than, and the solution in the receiver gives lower peaks, it is necessary to wash out the fridge with double-distilled water and repeat the assay. Oxidation itestosterone acid by air oxygen on the inner surface of the tube opposite the refrigerator at the time when the appliance is not working, is a common cause of underestimation of the results of determination of sulfur. If the solution in the receiver gives a much higher peaks, we tested the correction in the reference experiment, as indicated lower

E.

3.2. The control experience

For the newly assembled unit conduct multiple testing corrections in the reference experiment while passing a gas through boiling solvent mixture for 30 min. the Amendment reference experiment (in units of micrograms of sulfur in 10 cmof solution) is determined by the ratio of the peak in the corresponding solution to the peak height obtained in the recovery of 0.2 µg of sulfate sulfur. If polarogram solution in the control experiment did not observe the peak of sulfur, and there is a inflection point on a polarographic curve at the potential of peak sulfur, the wave height and take half the difference of the ordinates of inflection points and minima on the positive branch of the peak.

The installation think is workable, if the amendment reference experiment for 30 minutes does not exceed 0,02 g of sulphur when the mass fraction of sulfur in Gaul no more than 5·10% and 0.2 µg of sulfur at high mass fractions of sulfur.

The completeness of the distillation of sulfur daily check in the morning. Amendment control experience check in the morning and after each transition, the distillation of large quantities of sulfur in the Stripping of small amounts of sulfur.

3.3. Calibration setup

For the calibration setup hold recovery and Stripping of sulfur from 0.2 cmworking solution of sulphate sulphur as specified in claim 3.1. The installation will graduate one or two times during the working day.

4. ANALYSIS

After establishing the completeness of the distillation, sulfur and amendments the reference experiment (sec. 3) reducing the mixture is cooled to room temperature. In the receiver 4 is poured new portion (10 cm) polarographic background, raise the refrigerator and 5 in the reaction flask 2 enter the portion of gallium by mass of 0.5−2 g, depending on the sulfur content. Lower the refrigerator, turn up the heat of the hotplate 1 and lead the dissolution of gallium and recovery of the sulfur by boiling the recovery of the mixture.

After the dissolution of gallium register polarogram solution in the receiver in the conditions of claim 3.1 and determine the correction reference experiment for a time equal to the time of the dissolution of the sample of gallium.

One portion of the replacement mixture is allowed to gradually carry out the analysis of several batches of gallium, while the total mass of gallium analyzed do not exceed 3 g.

5. PROCESSING OF THE RESULTS

5.1. Mass fraction of sulfur () in percent is calculated by the formula

,

where is the mass of sulfur in solution sulphate sulphur, is introduced for the calibration of the installation, mcg;

 — arithmetic average peak height prerogrative of the solution after introduction of the sample minus the height of the peak in the reference experiment for the dissolution time of the sample of the sample, mm;

the weight of gallium, g;

 — the arithmetical mean height of the peak obtained during the calibration of an instrument, minus the height of the peak in the reference experiment for 30 min.

5.2. The analysis result should be the arithmetic mean of two parallel definitions, drawn from separate batches.

The allowable discrepancy of the two results of parallel measurements and the two results of the analysis (the difference between larger and smaller) with confidence probability of 0.95 is given in the table.

Permitted discrepancies for the intermediate mass fraction of sulfur is calculated using linear interpolation.

5.3. Control of the correctness analysis is carried out by additives according to GOST 25086.