GOST 14338.3-91

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  ГОСТ 14338.3-91

GOST 14338.3−91 Molybdenum. Methods for determination of phosphorus

GOST 14338.3−91

Group B59

STATE STANDARD OF THE USSR

MOLYBDENUM

Methods for determination of phosphorus

Molybdenum. Methods for determination of phosphorus

AXTU 1709

Date of introduction 1993−01−01

INFORMATION DATA

1. DESIGNED AND MADE TC N 108 «TVERDOSPLAV"

DEVELOPERS

Y. A. Abramov, A. I. Skrypnyk, S. N. Suvorov, G. V. Onuchina, A. G. Matyushina

2. APPROVED AND promulgated by the Decree of Committee of standardization and Metrology of the USSR from 27.09.91 N 1526

3. REPLACE GOST 14338.3−82

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard establishes photometric methods for determination of phosphorus (at a mass fraction of phosphorus from from 0.0002 to 0.015%) in the metal molybdenum, molybdenum oxide and ammonium molybdate.

1. GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 29103.

2. METHOD KYLINALOVE ORANGE (IN THE MASS FRACTION OF PHOSPHORUS FROM 0,0002 TO 0,01%)

2.1. The essence of the method

The method is based on the formation of complex compounds of phosphorus and molybdenum heterophilically with selenology orange. Silicon and arsenic complex compound with selenology orange in these conditions do not form.

2.2. Measuring instruments, accessories, reagents and materials

Analytical scale of any type that allows you to weigh a maximum error of 0.0002 g.

Photoelectrocolorimeter or spectrophotometer of any type.

Muffle furnace providing heating up to 500 °C.

The unit of household according to GOST 14919.

Ammonium (sodium) molybdate according to GOST 3765, recrystallized, solution with a mass fraction of 10%.

70 g of salt are dissolved in 400 cmof hot water and filtered through a dense filter. To the solution was added to 250 cmof ethyl alcohol (rectified), leave for 1 hour to settle, and then the crystals are sucked off on a Buchner funnel, washed several times with water and with alcohol and dried in air.

Ammonium disodium phosphate according to GOST 3772.

Standard solution A: 0,426 g twosemester ammonium phosphate is transferred to a volumetric flask with a capacity of 500 cm, is diluted to the mark with water and mix.

1 cmof the solution contains 0.0002 g of phosphorus.

Standard solution B: prepare by diluting 1 cmof the solution And water in a volumetric flask with a capacity of 100 cm.

1 cmof solution B contains 0,000002 grams of phosphorus.

Potassium hydroxide, solution with a mass fraction of 10%.

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

Selenology orange solution with a mass fraction of 0.1%, prepare at least 10 h before use, the reagent tested for the suitability to the reaction of formation of the complex with the molybdophosphoric heterocycles: 10 cmof acetone is added 0.1 cm(3−4 drops) of the solution kylinalove orange with a mass fraction of 0.1%. If the solution remains colourless or a slightly pink coloration of the reagent suitable for analysis, if the color purple — reagent complex with the molybdophosphoric heteropolyacid is formed.

Hydrochloric acid according to GOST 3118.

Phenolphthalein solution with a mass fraction of 0.1%.

Rectified ethyl alcohol according to GOST 183

00.

2.3. Analysis

Depending on the mass fraction of phosphorus take the sample in accordance with table.1.

Table 1

2.3.1. A portion of the molybdenum oxide is placed in a beaker with a capacity of 100 cm, add 10 cmof potassium hydroxide solution with a mass fraction of 10% and heated on a hotplate until complete dissolution of the sample.

2.3.2. Ammonium molybdate is transferred to molybdenum oxide by calcination at a temperature of 400−450 °C and then dissolved according to claim 2.3.1.

After cooling to room temperature, the obtained alkaline solution is neutralized with nitric acid (1:1) phenolphthalein indicator and add 10 cmof the acid in excess. The solution is heated to boiling.

If you get a precipitate, it is dissolved in potassium hydroxide solution with a mass fraction of 10% and then neutralized to phenolphthalein indicator to the solution with nitric acid, adding 10 cmin excess. The solution was cooled to room temperature and transferred to a volumetric flask with a capacity of 100 cm, top up with water to a volume of approximately 80 cm.

Depending on the mass of sample analyzed sample is added to a solution of ammonium with mass fraction 10% in volume, given in table.2.

Table 2

Then pipette the flask was injected 5 cmkylinalove orange solution with a mass fraction of 0.1%, made up to the mark with water and mix. The solution is kept for 45 min for formation of stable complex compounds. At the expiration of this time the optical density of colored solution is measured on photocolorimeter with a green light filter (wave length 540 nm) in a cuvette with a thickness of the light absorbing layer was 50 mm.

At the same time spend three reference experiment for the determination of phosphorus reagents. To a solution of the reference experiment a solution of ammonium with mass fraction 10% in volume of 10 cm. The solution to the mean value of optical density used as a comparison solution.

2.3.3. A portion of metallic molybdenum with a mass of 0.5 g is dissolved in 20 cmof a mixture consisting of three volumes of hydrochloric acid and one volume of nitric acid. The solution was evaporated to dryness on a hot plate.

Then add 10 cmof water and again evaporated, then add 10 cmof potassium hydroxide solution with a mass fraction of 10% and heated on a hotplate until complete dissolution of the precipitate.

After cooling to room temperature, the solution is neutralized with nitric acid (1:1) phenolphthalein indicator and add 10 cmof the acid in excess. Top up with water approximately to a volume of 80 cmand leave for 10 minutes Then pipette the flask was injected 5 cmkylinalove orange solution with a mass fraction of 0.1%.

Further analysis is carried out as specified in clause 2.3.1.

2.3.4. To build a calibration curve in a volumetric flask with a capacity of 100 cmpoured from 0.5 to 5.0 cm(every 0.5 cm) of solution B. to Introduce 10 cmof nitric acid (1:1), add water to volume of about 80 cm, add 10 cmof molybdate ammonium solution with a mass fraction of 0.1%, left for 10 min to develop the color of the resulting heteroalicyclic. Then pipette add 5 cmkylinalove orange solution with a mass fraction of 0.1%, made up to the mark with water, mix and leave for 45 min for formation of stable colored complex compounds. At the expiration of this time the optical density of colored solution is measured on photocolorimeter with a green light filter (wave length 540 nm) in a cuvette with a thickness of the light absorbing layer was 50 mm.

As a solution comparison solution is used in the reference experiment with an average value of optical density from three parallel experiments.

On the found values of optical densities of solutions and their corresponding concentration of phosphorus build calibration charts

.

2.4. Processing of the results

2.4.1. Mass fraction of phosphorus () in percent is calculated by the formula

,

where is the mass of phosphorus in the sample solution, found by calibration schedule g;

 — the weight of the portion,

2.4.2. Allowable absolute discrepancies in the results of parallel measurements at a confidence level =0.95 does not exceed the values given in table.3.

Table 3

3. METHOD WITH THE USE OF ASCORBIC ACID AND POTASSIUM ARMENONVILLE (WHEN THE MASS FRACTION OF PHOSPHORUS FROM 0.0005 TO 0.015%)

3.1. The essence of the method

The method is based on the formation of phosphorus-molybdenum heteroalicyclic and the restoration of its ascorbic acid in the presence of potassium animeillustrated after separation of the phosphorus by the hydroxide of beryllium.

3.2. Measuring instruments, accessories, reagents and materials

The generic type ion meter EV-74.

Trilon B (III chelating agent), disodium salt ethylenediaminetetraacetic acid according to GOST 10652, a solution with a mass fraction of 10%; prepared by heating.

Beryllium sulfate solution of concentration 1 g Ve/DM. Dissolve 19,65 g of beryllium sulphate in 1 DMof water.

Ammonia water according to GOST 3760.

The washing liquid: 500 cmof water was added 30 cmof the solution Trilon B, 15 cmof ammonia and dilute with water to 600 cm.

Perchloric acid, density 1.5 g/cm, diluted 1:1.

Ammonium molybdate according to GOST 3765.

The reaction mixture of 1.74 g of ammonium molybdate dissolved in 100 cmof water is added 21 cmsulfuric acid, cooled and made up to 250 cmwith water.

Ascorbic acid, a solution of concentration 20 g/DM.

Potassium armanavicius (antimoniate potassium on the other 6−09−803), solution concentration of 3 g/DM.

Ammonium bromide according to GOST 19275.

Indicator paper «Congo».

As well as measuring instruments, accessories, reagents and materials, resulted in

2.2.

3.3. Preparation of samples for analysis

Depending on the mass fraction of phosphorus take the sample in accordance with table.4.

Table 4

3.3.1. Dissolution of the samples is carried out according to claim 2.3.1.

3.4. Analysis

The obtained alkaline solutions are neutralized with nitric acid (1:1) on the indicator paper «Congo».

Pour 50 cmof the solution Trilon B, 8 cmof beryllium sulfate solution, dilute with water to 100−120 cmand boil for 2−3 min.

In the hot solution is poured ammonia solution till pH value is 9.5−10 and again boil for 2−3 min.

The solution was cooled in running water and the precipitate is filtered on a filter of medium density.

The filter residue is washed 5−6 times with wash fluid. The filter cake is dissolved in 30 cmof warm hydrochloric acid (1:1). The filtrate collected in a beaker with a capacity of 50 cm*, add 3 cmof perchloric acid (1:1) and evaporate the solution until copious fumes of perchloric acid.
________________
* If the arsenic content in the sample exceeds twice the phosphorus content, after dissolution of the hydroxide of beryllium in the environment hydrochloric acid add 0.1 g of ammonium bromide and evaporated to dryness. Add 10 cmof hydrochloric acid, and 0.1 g of ammonium bromide and repeat the evaporation to dryness.

Then pour 25 cm* and heated to dissolve the salts. The cooled solution is transferred to a volumetric flask with a capacity of 50 cm, pour 2.5 cmof the reaction mixture, 5 cmof ascorbic acid and 0.5 cmof a solution of potassium animeillustrated. After perelivania each of the reagent contents of the flask stirred. Then dilute to the mark with water and mixed again.
_________________
* The text matches the original. — Note the manufacturer’s database.

Optical density of the solution measured on a spectrophotometer at a wavelength of 825 nm on photoelectrocolorimeter at a red light filter (wavelength 750 nm) in a cuvette with a thickness of the absorbing layer is 50 mm.

As a solution comparison solution is used in the reference experiment with an average value of optical density of three parallel results on the amount of phosphorus in the reaction

tiwah.

3.5. Construction of calibration curve

In glasses with a capacity of 50 cmare selected from 1 to 8 cmstandard solution B, and poured 3 cmof perchloric acid (1:1). The solution was evaporated to copious fumes of perchloric acid. To the cooled solution poured 25 cmof water and transfer the solution into volumetric flask with a capacity of 50 cm, pour 2.5 cmof the reaction mixture, 5 cmof ascorbic acid solution and 0.5 cmof a solution of potassium animeillustrated. After perelivania each of the reagent contents of the flask stirred. Then dilute to the mark with water and mix again.

Optical density of the solution measured on a spectrophotometer at a wavelength of 825 nm or photoelectrocolorimeter with a red light filter (wavelength 750 nm

).

3.6. Processing of the results

3.6.1. Mass fraction of phosphorus () in percent is calculated by the formula

,

where is the mass of phosphorus was found in the calibration schedule,

 — the weight of the portion of the sample,

3.6.2. Discrepancies in the results of parallel measurements at a confidence level =0.95 does not exceed the values given in table.5.

Table 5