GOST 22974.11-96

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  ГОСТ 22974.11-96

GOST 22974.11−96 fused welding Fluxes. Methods for determination of calcium fluoride

GOST 22974.11−96

Group B09

INTERSTATE STANDARD

FUSED WELDING FLUXES

Methods for determination of calcium fluoride

Melted welding fluxes.
Methods of calcium fluoride determination

ISS 77.040
AXTU 0809

Date of implementation 2000−01−01

Preface

1 DEVELOPED by the Interstate technical Committee for standardization MTK 72; the Institute of electric them. E. O. Paton of NAS of Ukraine

SUBMITTED to the State Committee of Ukraine for standardization, Metrology and certification

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 9 dated April 12, 1996)

The adoption voted:

3 Resolution of the State Committee of the Russian Federation for standardization and Metrology, dated April 21, 1999 N 134 inter-state standard GOST 22974.11−96 introduced directly as state standard of the Russian Federation from January 1, 2000

4 REPLACE GOST 22974.11−85

1 Scope

This standard specifies pyrohydrolysis and titrimetric chelatometric methods for the determination of calcium fluoride at a content of from 1.5 to 65%.

2 Normative references

The present standard features references to the following standards:

GOST 61−75 acetic Acid. Specifications

GOST 83−79 Sodium carbonate. Specifications

GOST 1027−67 Lead (II) acetate 3-water. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3770−75 Ammonium carbonate. Specifications

GOST 4233−77 Sodium chloride. Specifications

GOST 4234−77 Potassium chloride. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 4463−76 Sodium fluoride. Specifications

GOST 5817−77 tartaric Acid. Specifications

GOST 9147−80 Glassware and equipment lab porcelain. Specifications

GOST 9428−73 Silicon (IV) oxide. Specifications

GOST 10652−73 Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid 2-water (Trilon B)

GOST 18300−87 ethyl rectified technical. Specifications

GOST 22974.0−96 fused welding Fluxes. General requirements for methods of analysis

3 General requirements

General requirements for methods of analysis GOST 22974.0.

4 Pyrohydrolysis method for the determination of calcium fluoride

4.1 the essence of the method

The method is based on the decomposition of calcium fluoride with water vapor at a temperature of 1300 °C in the presence of a catalyst. The separated hydrofluoric acid with an excess of a couple likes to the receiver, where is titrated with sodium hydroxide.

4.2 Equipment, reagents and solutions

Setup for determination of calcium fluoride (figure 1).

Figure 1 — Installation for determination of calcium fluoride

1 — rinsing bottle to purify the air or oxygen, filled with a solution of sodium hydroxide
mass concentration of 0.2 g/cm; 2 — spherical tube filled with glass wool to trap
water droplets, with alkali; 3 — stainless steel tube with outer diameter 20 mm internal 18 mm
length 220 mm, which includes a tube 10 and tightly fastened with a clamp; 4 — stainless steel tube
with a diameter of 10 mm, welded to the tube 3; 5 — flask to generate steam; 6 — electric stove;
7 — porcelain boat-N 2 according to GOST 9147, pre-calcined in a muffle furnace
at a temperature of 900−1000 °C for 4−5 h; 8 — tube furnace with SIC
a heater that provides temperature (1300±20) °C and installed with a slope of 4° in
the receiver; 9 — thermometer; 10 — of porcelain or quartz tube internal
diameter 20−22 mm; 11, 13 — rubber gasket; 12 — tank for cooling water tube;
14 — forston; 15 — receiver for the titration of hydrofluoric acid

Figure 1 — Installation for determination of calcium fluoride

The hook with which the boat was placed in a tube and extracted from it, is made of heat-resistant wire with a diameter of 3−5 mm, length 500−600 mm.

Sodium hydroxide according to GOST 4328, solution mass concentration of 0.2 g/cmand a solution with molar concentration of the equivalent 0,02 mol/DM.

Aluminum oxide, anhydrous, calcined at 1100 °C for 1 h.

The technical rectified ethyl alcohol according to GOST 18300.

Methyl red (indicator).

Methylene blue (indicator).

Mixed indicator: 0.125 g methyl red and 0,083 g of methylene blue dissolved in 100 cmof ethanol; store in a dark bottle.

Hydrochloric acid according to GOST 3118 molar concentration of 0.02 mol/DM(fixanal).

The mass concentration of sodium hydroxide set at the standard sample of the flux. The analysis of the standard sample carried out under the same conditions as the analysis of the investigated sample.

The mass concentration of sodium hydroxide solution , g/cmcalcium fluoride, is calculated by the formula

, (1)

where  — mass fraction of calcium fluoride in the standard sample, %;

 — weight of standard sample, g;

 — the amount of sodium hydroxide, spent on titration, sm.

The mass concentration of sodium hydroxide can be set to the titrated solution of hydrochloric acid (fixanal): 25 cmacid solution the molar concentration of 0.02 mol/DMare placed in a titration flask, add 2−3 drops of mixed indicator and titrated with alkali solution before moving pink coloring in green.

The mass concentration of sodium hydroxide solution , g/cmcalcium fluoride, is calculated by the formula

, (2)

where  — relation to ;

 — the volume of hydrochloric acid molar concentration of 0.02 mol/DM;

 — the volume of alkali.

4.3 analysis

Weighed flux weighing 0.1−0.2 g is placed in a porcelain boat containing 0.2−0.4 g of aluminum oxide. Pumps the contents are thoroughly mixed. A boat placed in a porcelain tube, heated to a temperature of 1250−1350 °C, and close the tube with a rubber stopper. In a porcelain tube through the stump of the tube 3 serves air or oxygen at a rate of 3−5 bubbles per second at the same time with steam.

Pyrohydrolysis formed when hydrofluoric acid is supplied to the receiver 15, where the pre-pour 50 cmof water and 5−6 drops of mixed indicator.

Hydrofluoric acid is titrated with a sodium hydroxide solution with molar concentration of the equivalent 0,02 mol/luntil the color changes from purple to green. End the titration when the color of the solution does not change within 2 min.

4.4 Processing of results

4.4.1 Mass fraction of calcium fluoride , %, is calculated by the formula

, (3)

where is the mass concentration of the sodium hydroxide solution, g/cmcalcium fluoride;

 — the volume of sodium hydroxide solution consumed for titration, cm;

 — the weight of the portion of the flux,

4.4.2 Standards of accuracy and standards for monitoring the accuracy of determining the mass fraction of calcium fluoride are shown in table 1.


Table 1

Percentage

5 Titrimetric chelatometric method for the determination of calcium fluoride

5.1 the essence of the method

The method is based on the deposition of fluorine ions in the form of perchloride lead. The excess of lead is titrated with a solution of Trilon B.

5.2 Reagents and solutions

Nitric acid according to GOST 4461, diluted 1:1.

Ammonia water according to GOST 3760, diluted 1:1.

Ammonium carbonate according to GOST 3770.

Potassium chloride according to GOST 4234.

The anhydrous sodium carbonate according to GOST 83.

Sodium chloride according to GOST 4233, solution mass concentration of 0.05 g/cm.

Lead acetate according to GOST 1027, solution mass concentration of 0.025 g/cm.

Tartaric acid according to GOST 5817, solution mass concentration of 0.05 g/cm.

Acetic acid according to GOST 61.

Silicon (IV) dioxide according to GOST 9428.

Methyl orange (indicator), the solution of the mass concentration of 0.001 g/cm.

Eriochrome black (light): 0.2 g of the indicator is triturated with 20 g of potassium chloride.

Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid 2-water (Trilon B) according to GOST 10652, solution with molar concentration of equivalent of 0.05 mol/DM: 9.3 g Trilon B dissolved in 300 cmof water. The solution was filtered into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

Sodium fluoride according to GOST 4463, standard solution: 2,210 g of sodium fluoride is dissolved in water and diluted to 1000 cmof water in a volumetric flask. The solution has a mass concentration of 0.001 g/cm.

The mass concentration of the solution Trilon B set for fluorine: 50 cmstandard solution was transferred to a beaker with a capacity of 300 cm, add 10 drops of acetic acid, 20 cmof sodium chloride solution from the burette 25 cmof a solution of acetate of lead. The solution was stirred, heated to a temperature of 60−70 °C, then mixed to the sediment, then leave for 12 h

The solution with the precipitated sludge is transferred to a volumetric flask with a capacity of 250 cm, is diluted to the mark with water and filtered into a dry beaker through a dry filter «white ribbon», discarding first portion of filtrate.

Take 50−100 cmof filtrate into the conical flask with a capacity of 250 cm, flow 10 cmof tartaric acid, 10 cmof ammonia (1:1), add 0.1 g of eriochrome black indicator and titrate the excess of lead with a solution of Trilon B before transition of colouring from lilac-purple to bright blue.

Mass concentration of Trilon B , g/cmcalcium fluoride, is calculated by the formula

, (4)

where  — the volume of a standard solution of sodium fluoride, cm;

 — the ratio of fluoride to calcium fluoride;

 — the volume of solution of acetate of lead, taken with excess, see;

 — volume of solution Trilon B, used for titration of excess of acetate of lead, cm;

 — the ratio between the volumes of the solutions of acetate of lead and Trilon B.

Determine the ratio : 5 cmof a solution of acetate of lead is placed in a conical flask with a capacity of 250 cm, add 50 cmof water, 10 cmof tartaric acid, 10 cmof ammonia (1:1), 0.1 g of the indicator eriochrome black and titrated until the transition of color from lilac-purple to bright blue.

The ratio is calculated by the formula

, (5)

where is the volume of solution of acetate of lead, taken for titration, cm;

 — volume of solution Trilon B, spent on titration, sm.

5.3 analysis

The linkage of flux with a mass of 0.5 g (for the mass concentration of calcium fluoride of 1.5−40%) or 0.25 g (with a mass fraction of calcium fluoride 40−65%) is mixed with 0.2 g of silica and 5 g of anhydrous sodium carbonate and fused in a platinum crucible with lid at a temperature of 950−1050 °C for 20−30 min. the Melt was poured onto a polished plate of stainless steel.

The crucible with the melt is placed in a beaker with a capacity of 300−400 cm, 50 cm pour thehot water, covered with glass and kept in a warm place until the complete decomposition of water.

The crucible is removed from the beaker and washed several times with water. Solution and the precipitate was transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

The solution was filtered in a dry flask through a dry filter «white ribbon», discarding first portion of filtrate. Take 50 cmof the filtrate in a beaker with a capacity of 300 cm, add 2−3 drops of methyl orange and acidified with nitric acid (1:1) until orange colour, add 4−5 g of ammonium carbonate and boiled until the odour of ammonia (the silicic acid is excreted in the form of the gelatinous sediment). The solution was filtered into a glass with a capacity of 300 cmthrough cotton wool and washed 8−10 times with hot water. The filtrate is acidified by methyl orange nitric acid (1:1) to change the color of the solution, add 10 drops of acetic acid, 20 cmof sodium chloride solution from the burette 25−50 cmof a solution of acetate of lead. The solution was stirred, heated to a temperature of 60−70 °C, then mixed to the sediment, then leave for 12 h

The solution with the precipitated sludge is transferred to a volumetric flask with a capacity of 250 cm, is diluted to the mark with water and filtered into a dry beaker through a dry filter «white ribbon», discarding first portion of filtrate.

50−100 cmof the filtrate was transferred to a conical flask with a capacity of 250 cm, flow 10 cmof tartaric acid, 10 cmof ammonia (1:1), add 0.1 g of eriochrome black indicator and titrate the excess of lead with a solution of Trilon B before transition of colouring from lilac-purple to bright

blue.

5.4 processing of the results

5.4.1 Mass fraction of calcium fluoride , %, is calculated by the formula

, (6)

where is the volume of solution of acetate of lead, taken for deposition of fluorine-ion, cm;

 — volume of solution Trilon B, used for titration of excess of acetate of lead, cm;

 — the ratio between the volumes of the solutions of acetate of lead and Trilon B;

 — mass concentration of the solution Trilon B, expressed in g/cmof calcium fluoride;

 — the weight of the portion corresponding to aliquote part of the solution

G.

5.4.2 Norms of accuracy and norms control the accuracy of determining the mass fraction of calcium fluoride are shown in table 1.