GOST 22536.3-88

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  ГОСТ 22536.3-88

GOST 22536.3−88 (ST SEV 485−75) carbon Steel and unalloyed cast iron. Method of determination of phosphorus

GOST 22536.3−88
(ST CMEA 485−75)

Group B09

STATE STANDARD OF THE USSR

CARBON STEEL AND UNALLOYED CAST IRON

Methods for determination of phosphorus

Carbon steel and unalloyed cast iron.
Methods for determination of phosphorus

AXTU 0809

Valid from 01.01.90
to 01.07.95*
______________________________
* Expiration removed
Protocol N 4−93 inter-state Council
for standardization, Metrology and certification.
(IUS N 4, 1994). — Note the CODE.

INFORMATION DATA

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

PERFORMERS

D. K. Nesterov, PhD. tech. Sciences; S. I. Rudyuk, PhD. tech. Sciences; S. V. Spirina, PhD. chem. Sciences (head of subject); V. F. Kovalenko, PhD. tech. science; N. N. Gritsenko, PhD. chem. Sciences; E. V. Podpruzhnikov; L. I. birch

2. APPROVED AND put INTO EFFECT by decision of the USSR State Committee for standards from 25.08.88 N 3018

3. The standard complies ST SEV 485−75 in the part of the gravimetric analysis method of carbon steel and unalloyed cast iron

4. REPLACE GOST 22536.3−77

5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard specifies the photometric (with a mass fraction of phosphorus 0,005−0,25%), titrimetric (mass fraction in phosphorus 0,02−2,5%) and gravimetric (for the mass concentration of 0.01 to 2%) methods for determination of phosphorus in carbon steel and unalloyed cast iron.

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 22536.0−87.

1.2. The error analysis result (at p = 0.95) does not exceed the limit given in table.1, when the conditions are met:

the discrepancy between the results of two (three) parallel dimensions should not exceed (with a confidence probability = 0,95) of the values given in table.1;

played in the standard sample, the value of the mass fraction of phosphorus should not vary from certified more than acceptable (at a confidence level =0,85) the value given in table.1.

If any of the above conditions, a second measurement of the mass fraction of phosphorus. If in repeated measurements the precision requirement of the results are not met, the results of the analysis recognize the incorrect measurements cease to identify and eliminate the causes of violation of the normal course of analysis.

The divergence of the two middle results of an analysis performed under different conditions (for example, when the control intralaboratory reproducibility) shall not exceed (at p = 0.95) values are given in table.1.

Table 1

2. PHOTOMETRIC METHOD

2.1. The essence of the method

The method is based on the reaction of formation of the molybdophosphoric yellow heteropolyblue , restore it to a blue complex compounds with ions of bivalent iron in the presence of hydroxylamine, thiourea in the presence of copper sulfate or ascorbic acid in the presence of potassium animeillustrated and subsequent measurement of light absorption of the solutions at =680−900 nm =nm or 680−880 =830−920 nm, respectively.

2.2. Equipment and reagents

Spectrophotometer or photoelectrocolorimeter.

The platinum crucible according to GOST 6563−75.

The glassy carbon crucible No. 4.

Nitric acid GOST 4461−77 or GOST 11125−84 diluted 1:1, 1:10 and 5:95.

Hydrochloric acid by the GOST 3118−77 or GOST 14261−77 diluted 1:1, 1:3, 1:20 and a density of 1.105 g/cm.

For preparation of a solution of hydrochloric acid with a density of 1.105 g/cm: 560 cmof hydrochloric acid diluted with water to 1 DMand stirred.

Sulfuric acid GOST 4204−77 or GOST 14262−78 and diluted 1:4.

Hydrofluoric acid according to GOST 10484−78.

Acid chloride of qualification «Kh. CH.» or «h. e. a.».

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

Sodium carbonate according to GOST 83−79.

Sodium atomistically according to GOST 4197−74, a solution with a mass concentration of 50 g/DM.

Potassium permanganate according to GOST 20490−75, a solution with a mass concentration of 40 g/DM.

Potassium phosphate according to GOST odnosemjannyj 4198−75.

Potassium antimoniate according to normative-technical documentation, solution with a mass concentration of 3 g/DM.

Alum salesonline for NTD, a solution with a mass concentration of 100 g/DM: gentoomaniac 100 g of alum was dissolved with heating in 150 cmof hydrochloric acid diluted 1:10, the solution is cooled, filtered in a volumetric flask with a capacity of 1 DMand dilute to the mark with water.

Ammonia water according to GOST 3760−79 diluted 1:1, 1:100.

Ammonium bromide according to GOST 19275−73, a solution with a mass concentration of 100 g/DM.

Ammonium molybdate 4-water, GOST 3765−78, recrystallized, solution with a mass concentration of 50 g/DM: 50 g of ammonium molybdate dissolved in 300 cmof water at 40 °C, the solution was filtered in a volumetric flask with a capacity of 1 DM, dilute to the mark with water and mix.

The solution should be stored in polyethylene or quartz container.

For recrystallization of ammonium molybdate in 250 g of reagent was dissolved in 400 cmof water when heated to 70−80 °C, the solution was filtered through a filter «white ribbon», cooled to room temperature, poured, with stirring, 300 cmof ethyl alcohol, allow sediment to settle for 1 h and filtered it, the filter «white ribbon» placed in a Buchner funnel, using a water vacuum pump. Precipitate was washed 2−3 times with ethanol and dried in air.

Hydroxylamine hydrochloride according to GOST 5456−79 or hydroxylamine sulfate according to GOST 7298−79, a solution with a mass concentration of 200 g/DM.

Thiourea according to GOST 6344−73, a solution with a mass concentration of 80 g/DM.

Copper (II) sulfate 5-water according to GOST 4165−78, a solution with a mass concentration of 10 g/DM.

Potassium sanitarily Piro, a solution with a mass concentration of 100 g/DM.

Radio engineering carbonyl iron according to GOST 13610−79.

Rectified ethyl alcohol GOST 18300−87 or GOST 5962−67.

Recovery blend: 150 cmof a solution of copper sulphate mixed with 700 cmof a solution of thiourea. After standing for 24 h the mixture was filtered through a dense filter, and the precipitate discarded.

Magnesium chloride 6-water according to GOST 4209−77.

Ammonium chloride according to GOST 3773−72.

Paper display «of the Congo».

Magnesia mixture: 50 g magnesium chloride and 100 g of ammonium chloride dissolved in 500 cmof water is added a slight excess of ammonia, leave the solution for 12 hours and then filtered, the precipitate on the filter tight. To the filtrate add hydrochloric acid (1:1) until the blue color of the indicator paper Congo.

The reaction mixture of 1.74 g of ammonium molybdate dissolved in 100 cmof water when heated, add 21 cmsulfuric acid, cool, add water to 250 cmand stirred; prepared prior to use.

Standard solution of phosphorus: 0,4393 g of single potassium phosphate, recrystallized and dried to constant weight at 100−105 °C, placed in a volumetric flask with a capacity of 1 DM, is dissolved in 100 cmof water, made up to the mark with water and mix.

1 cmof the solution contains 0.0001 g of phosphorus.

If necessary, set the mass concentration of a standard solution of phosphorus: 50 cmstandard solution is placed in a beaker with a capacity of 300 cm, add 5 cmof hydrochloric acid and 20 cmof magnesia mixture. Add ammonia solution till the odor, cooled to a temperature of not higher than 10 °C, vigorously stirred with a glass rod, add another 10 cmof ammonia and leave for 12 h

The precipitate was filtered off on a thick filter with a small amount of ashless filter-paper pulp and washed 12−15 times with cold ammonia solution (1:100). The filter with precipitate was placed in a calcined and weighed platinum crucible, dried, incinerated and calcined at 1000−1100 °C, then cooled and weighed. Simultaneously conduct control experience on the phosphorus content in the reagents.

The mass concentration of a standard solution (a), expressed in grams of phosphorus per 1 cmof a solution, calculated by the formula

,

where is the mass of sediment of magnesium pyrophosphate, respectively, in the analyzed sample and in the solution in the reference experiment, g;

0,2787 — the ratio of the mass of the precipitate of magnesium pyrophosphate to the phosphorus;

 — the volume of the solution taken for analysis, cm.

2.3. Analysis

2.3.1. The weight of steel or cast iron depending on the mass fraction of phosphorus (table.2) is placed in a flask or beaker with a capacity of 100 cmand dissolved by heating in 20−30 cmof hot nitric acid (1:1).

Table 2

After complete dissolution of the sample added dropwise a solution of potassium permanganate before rolling the brown precipitate of manganese dioxide (2−4 cm) and boil for 2−3 min. Then the solution was poured dropwise a solution of sodium attestatio to dissolve the precipitate and full enlightenment of the solution and boil to remove oxides of nitrogen.

The solution was evaporated to dryness, add 10 cmof hydrochloric acid and again evaporated to dryness. To the dry residue poured 15 cmof hydrochloric acid and heated to dissolve the salts, add 20−30 cmof water, cool and transfer the solution into volumetric flask with a capacity of 100 cm, the solution is topped up to the mark with water and mix.

If a precipitate of (graphite, silicic acid), it is separated by filtering the solution on filter medium density with a small number of filtrowanie mass. The filter cake was washed 5−6 times with hot hydrochloric acid solution (5:95) and 3−4 times with hot water.

The filter with the sediment is discarded if the mass fraction of silicon in the alloy does not exceed 1%.

When the mass fraction of silicon above 1% filter with the sediment was placed in a platinum crucible, dried, incinerated and calcined at 800−900 °C. the Precipitate is moistened with 2−3 drops of water, add 3−5 drops of sulfuric acid (1:4), 3−5 cmhydrofluoric acid and cautiously evaporate the contents of the crucible to dryness. The precipitate is fused in a crucible with 1−2 g of sodium carbonate at 1000−1100 °C for 10−15 min. the Melt is leached with water and filtered on a filter of medium density. The crucible is washed with water and add the filtrate to the main solution. The solution was evaporated to a volume of 50−60 cm, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Note. The operation of removing the silicon can be carried out using a glassy carbon crucible. For mounting steel or cast iron placed in a glassy carbon crucible and was dissolved with heating in 20−30 cmof hot nitric acid (1:1) and 5 cmhydrofluoric acid. The solution was evaporated to wet condition salts, after which pour 5 cmof nitric acid (1:1), 20 cmof water and boil the solution until complete removal of nitrogen oxides, then the analysis continues as described above.

If the mass fraction of arsenic in the analyzed sample is more than twice the mass fraction of phosphorus, then it is removed in the form of bromide. For the mass concentration of phosphorus less than 0.01% and remove any quantity of arsenic. For this purpose the solution, after oxidation of the phosphorus is evaporated to dryness. The dry residue is dissolved in 10 cmof hydrochloric acid and again evaporated to dryness. Then the dry residue is dissolved in 10 cmof hydrochloric acid, add 10 cmof a solution of bromide of ammonium, and evaporate the solution to dryness. Treatment with hydrochloric acid is carried out three times. To the dry residue poured 15 cmof hydrochloric acid and heated to dissolve the salts, add 20−40 cmof water.

The solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and p

peremeshivaya.

2.3.2. Determination of phosphorus using as a reducing agent ions of divalent iron in the presence of hydrochloride or sulfate of hydroxylamine (when the mass fraction of phosphorus from 0.05 to 0.25%).

In two volumetric flasks with a capacity of 100 cmis placed aliquote part of the resulting solution equal to 100 cm, flow 10 cmof water (in the case of sample of sample of 0.25 g of the flasks add 1−2 cmof the solution gentoomaniac alum) and ammonia solution prior to the precipitation of iron hydroxide which is then dissolved by adding dropwise hydrochloric acid with a density of 1.105 g/cm. Add 10 cmof a solution of hydroxylamine and leave on warm stove until discoloration of the solution. If the solutions remain yellowish, you need to add 1−2 drops of ammonia solution (1:1), the appearance of turbidity add 2−3 drops of hydrochloric acid with a density of 1.105 g/cm.

The solutions were cooled and poured 10 cmof hydrochloric acid solution with a density of 1.105 g/cm. In one of the volumetric flasks poured dropwise, with continuous stirring, 8 cmof a solution of molybdate of ammonium. The solution was stirred for 1−2 min until appearance of a blue color, made up to the mark with water and mix.

Absorbance is measured after 10 minutes on the spectrophotometer at a wavelength of 680−900 nm or photoelectrocolorimeter with a red light filter having a region of transmittance in the wavelength range of 620−640 nm. As a solution comparison aliquote use the second part, which adds all of the specified reagents, except molybdate ammonium solution. Simultaneously with the execution of the analysis carried out control experience for contamination of reagents. In aliquot part of the reference experiment add 5 cmof the solution gentoomaniac alum, water to a volume of 25−30 cmand neutralized with ammonia, then the analysis continues as described above.

From the values of absorbance of each test solution subtract the value of optical density in the reference experiment.

A lot of find phosphorus for the calibration chart or by comparison with standard samples

Ascom.

2.3.3. Determination of phosphorus with the use as the reducing agent of thiourea (when the mass fraction of phosphorus from 0.01 to 0.25%).

In two volumetric flasks with a capacity of up to 100 cmis placed aliquote part is 10 cmobtained according to claim 2.3.1 test solution, pour 15 cmof water and dropwise a solution of ammonia (1:1) prior to the deposition of iron hydroxide, which is dissolved by adding dropwise a hydrochloric acid solution with a density of 1.105 g/cm, and 2 cmin excess. To the obtained solution was added 10 cmreplacement mix, allow to stand for 1−2 minutes, add 10 cmof hydrochloric acid with a density of 1.105 cmand dropwise with continuous stirring in one of the flasks add 8 cmof a solution of molybdate of ammonium. The solution was stirred for 1−2 min, and then diluted to the mark with water and mix.

After 10 minutes measure the optical density of the solution on the spectrophotometer at =680−880 nm or photoelectrocolorimeter with a red light filter having a region of transmittance in the wavelength range of 620−640 nm. As a solution comparison aliquote use the second part of the sample, which is added all the reagents, except molybdate ammonium solution.

Simultaneously with the execution of the analysis carried out control experience for contamination of reagents. In aliquot part of the reference experiment add 5 cmof the solution gentoomaniac alum, water to a volume of 25−30 cmand neutralized with ammonia, then the analysis continues as described above.

From the values of absorbance of each test solution subtract the value of optical density in the reference experiment.

A lot of find phosphorus for the calibration chart or by comparison with standard samples

Ascom.

2.3.4. Determination of phosphorus using as a reducing agent ascorbic acid in the presence of potassium animeillustrated (when the mass fraction of phosphorus from 0.005 to 0.25%).

Two glasses with a capacity of 100 cmis placed aliquote part is 10 cmobtained according to claim 2.3.1 the test solutions (with mass fraction of phosphorus 0,005−0,02%) or 5 cm(for the mass concentration of phosphorus 0,02−0,25%), add 1−2 cmof perchloric acid (density 1.5 g/cm) and evaporated solutions before selecting the vapors.

Salt is dissolved in 20 cmof water when heated, add 3 cmof a solution of sodium sulphite and boil for 2−3 min. the Solutions were cooled to a temperature at least 20 °C. In one of the glasses poured 5 cmof the reaction mixture, 10 cmof ascorbic acid solution and 1 cmof a solution of potassium animeillustrated.

The solution was transferred to volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Optical density of the solution is measured after 10 minutes on the spectrophotometer at a wavelength of 880 nm or photoelectrocolorimeter with a filter having a transmission region 680−750 or 830−920 nm.

As a solution comparison aliquote use the second part to which was added all of the above reagents, except the reaction mixture.

The results of the analysis taking into account the amendments the reference experiment can be described by a calibration chart or by comparison with standard samples

Scam.

2.3.5. Construction of calibration curve

In nine conical flasks or beakers placed sample of carbonyl iron, corresponding to the weight of the sample. In eight of them add 0,5; 1,0; 2,0; 3,0; 4,0; 5,0; 6,0 and 7.0 cmstandard solution of phosphorus. Ninth, the flask is used for the reference experiment on the phosphorus content in the reagents.

Flasks poured 20−30 cmof nitric acid (1:1) and heated until complete dissolution of the sample, are added dropwise a solution of potassium permanganate before rolling the brown precipitate of manganese dioxide and boiled for 2−3 min. Then the solution was poured dropwise a solution of sodium attestatio to dissolve the precipitate and full enlightenment of the solution and boil to remove oxides of nitrogen.

The solution was evaporated to dryness, add 10 cmof hydrochloric acid and again evaporated to dryness. To the dry residue poured 15 cmof hydrochloric acid and heated to dissolve the salts, add 20−30 cmof water, cool and transfer the solution into volumetric flask with a capacity of 100 cm. The solution was topped to the mark with water and mix.

In the case of determination of phosphorus using as a reducing agent ions of divalent iron in the presence of hydrochloric acid hydroxylamine or thiourea, taken aliquot part of the solution, equal to 10 cm, which corresponds to 0,000005; 0,000010; 0,000020; 0,000030; 0,000040; 0,000050; 0,000060 and 0,000070 g of phosphorus.

In the case of determining phosphorus with ascorbic acid taken aliquot part of the solution, equal to 5 cm, which corresponds to: 0,0000025; 0,0000050; 0,0000100; 0,0000150; 0,0000200; 0,0000300 and 0,0000350 g of phosphorus.

Further analysis is carried out as described in PP.2.3.2, 2.3.3 or 2.3.4.

As a solution comparison, using aliquot part of the solution in the reference experiment, which added all the reagents, except molybdate ammonium solution (if the analysis is carried out for PP.2.3.2. or 2.3.3.), or solution of the reaction mixture, if claim 2.3.4.

On the found values of optical density-adjusted reference experiment and their corresponding mass values of phosphorus build a calibration curve. Allowed construction of calibration curve in the coordinates: the optical density is the mass fraction of phosphorus

.

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 was found in the calibration schedule g;

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

2.4.2. Norms of accuracy and norms control the accuracy of determining the mass fraction of phosphorus are given in table.1.

3. TITRIMETRIC METHOD

3.1. The essence of the method

The method is based on deposition of oxidized to the pentavalent state of the phosphorus in the form of a complex of the molybdophosphoric yellow color, dissolving the precipitate in sodium hydroxide solution and titrate the excess sodium hydroxide with nitric acid.

3.2. Reagents and solutions

A platinum crucible according to GOST 6563−75.

A glassy carbon crucible No. 4.

Hydrochloric acid by the GOST 3118−77.

Nitric acid GOST 4461−77 or GOST 11125−84 and diluted 1:1, 1:10 and 1:100.

Potassium permanganate according to GOST 20490−75 solution with a mass concentration of 40 g/DM.

Potassium nitrate according to GOST 4217−77, a solution with a mass concentration of 10 g/DM.

Hydrofluoric acid according to GOST 10484−78.

Sodium atomistically according to GOST 4197−74, a solution with a mass concentration of 50 g/DM.

Sodium carbonate according to GOST 83−79.

Ammonium bromide according to GOST 19275−73, a solution with a mass concentration of 100 g/DM.

Potassium bromide according to GOST 4160−74 solution with a mass concentration of 100 g/DM.

Ammonium molybdate according to GOST 3765−78.

Ammonia water according to GOST 3760−79.

Ammonium radamisty, a solution with a mass concentration of 100 g/DM.

Barium hydroxide, 8-water according to GOST 4107−78.

Oxalic acid according to GOST 22180−76, recrystallized and dried to constant weight at 110−120 °C.

The lime soda.

Rectified ethyl alcohol GOST 18300−87 or GOST 5962−67.

Molybdenum liquid: 36 g ammonium molybdate dissolved in 30 cmof ammonia solution and 50 cmof water; 115 cmof ammonia solution carefully poured in 575 cmof nitric acid (1:1) and added 230 cmof water. The resulting solutions are cooled and mixed, gently infusing the first solution in the second with strong shaking to produced white turbidity disappeared. Thus it is necessary to periodically cool the solution, avoiding its heating. The solution was then aged for 48 h; before using filtered.

The indicator phenolphthalein in NTD, alcohol solution with a mass concentration of 10 g/DM; 1 g of phenolphthalein is dissolved in 60 cmof ethanol and add 40 cmof water.

Water neutral: to 1 DMwith distilled water, from which previously removed carbon dioxide by boiling for 2−3 h, poured 5cmof solution of phenolphthalein and the amount of standard sodium hydroxide solution to a persistent pink color. Then to the solution was added dropwise a standard solution of nitric acid to disappearance of color. 50 cmneutralized water should be painted in pink color from the addition of one drop of a standard solution of sodium hydroxide.

Sodium hydroxide according to GOST 4328−77, standard solution: 35 g of sodium hydroxide dissolved in 10 DMof cold water, freed from carbon dioxide pre-boiling for 2−3 h. To the solution add 5 g of barium hydroxide, stirred and allowed to stand for 2−3 days until the precipitate barium carbonate has settled completely. The solution is stored in bottles closed with a rubber stopper with two holes: one of them is inserted into the absorber with soda lime, the other a siphon tube with a tap, not reaching to the bottom of the bottles to 0.5 cm, with a bent towards the top end.

Sivunirmut clear solution into another bottle and store as above.

Nitric acid, standard solution: 50 cmof nitric acid was placed in a bottle and diluted to a volume of 10 DMof water, from which previously removed carbon dioxide by boiling for 2−3 h, 1 cmof nitric acid solution should be approximately equal to 1 cmMitrofanova solution of sodium hydroxide. The solution is stored in bottles closed with a rubber stopper with two holes: one of them is inserted into the absorber with soda lime, the other siphon tube (with stopcock), not reaching to the bottom of the bottles to 0.5 cm.

Set the ratio between the standard solutions of sodium hydroxide and nitric acid in a conical flask with a capacity of 250 cmpoured from a burette 25 cmof sodium hydroxide, add 25 cmneutral water and titrated with standard nitric acid until the disappearance of the pink color.

Coefficient (), which determines the ratio between the volumes of solutions of sodium hydroxide and nitric acid is calculated by the formula

,

where is the volume of sodium hydroxide solution taken for titration, cm;

 — the volume of nitric acid consumed for titration, sm.

The mass concentration of sodium hydroxide set on hanging oxalic acid or the standard sample, similar in composition and mass fraction of phosphorus to the sample.

The mass concentration of sodium hydroxide (), expressed in grams of phosphorus per 1 cmof a solution, calculated by the formula

,

where the linkage is oxalic acid, g;

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

To 0, 0214 — the ratio of the equivalent mass of phosphorus and oxalic acid.

3.3. Analysis

The weight of steel or cast iron depending on the mass fraction of phosphorus (see table.3) is placed in a conical flask with a capacity of 250 cmand dissolved by heating to 30−40 cmof nitric acid (1:1), covering the flask with a watch glass. After removing the glass, boil the solution to remove oxides of nitrogen.

Table 3

If a precipitate of (graphite, silicic acid) it is filtered off, the filter «white ribbon» with the addition of a small amount of ashless paper pulp, collecting the filtrate in a conical flask with a capacity of 300 cm. The filter cake is washed 6−8 times with hot nitric acid (1:100). The filter with the sediment is discarded if the mass fraction of silicon is less than 1.5%.

If the mass fraction of silicon in the analyzed sample exceeds 1.5%, the filter with the precipitate of silicic acid is placed in a platinum crucible, dried, incinerated and calcined at 800−900 °C. the Precipitate is moistened with 2−3 drops of water, add 8−10 drops of nitric acid, 3−5 cmhydrofluoric acid and cautiously evaporate the contents of the crucible to dryness. The residue is fused in a crucible with 1−2 g of sodium carbonate at 1000−1100 °C. the Melt is leached with nitric acid (1:10), by boiling. The crucible is washed with water, the resulting solution was filtered and added to the main filtrate. The solution was evaporated to 50−60 cm.

Note. The operation of removing the silicon can be carried out using a glassy carbon crucible as shown in claim 2.3.1.

To the boiling solution poured 5 cmof a solution of potassium permanganate, and boiled before rolling the brown precipitate of manganese dioxide. Without interrupting the heating, added dropwise a solution of sodium attestatio to dissolve the precipitate and produce a clear solution. The solution was boiled to remove oxides of nitrogen.

If the mass fraction of arsenic in the sample more than 10% of the mass fraction of phosphorus, or if the mass fraction of arsenic is unknown, the latter is removed by Stripping. To this end, the solution was evaporated to dryness, the dry residue add 10 cmof hydrochloric acid and again evaporate the solution to dryness. This operation is performed three times for the decomposition of nitrates. The dry residue was dissolved with heating in 15 cmof hydrochloric acid, poured 10 cmof a solution of bromide of ammonium or bromide of potassium, and evaporated to wet condition salts. Evaporation of the solution to the state of moist salts again, adding before steaming 10 cmof hydrochloric acid, then add 10 cmof nitric acid and evaporated to wet condition salts. The addition of nitric acid and evaporation to the state of moist salts is carried out two times. Then add 10 cmof nitric acid, 10−15 cmof water and heated to dissolve the salts.

The solution was cooled, poured to it ammonia solution prior to the precipitation of iron hydroxide, which dissolve with a few drops of nitric acid, then add 5 cmof the acid in excess.

The solution is heated to 50−60 °C, add 50 cmmolybdenum liquid and shaken for a few minutes before rolling phosphomolybdenum yellow precipitate of ammonium. Sediment is allowed to settle in a warm place for 2−3 hours

The precipitate was filtered off on the filter «blue ribbon» with the addition of a small amount of ashless paper pulp. Flask in which to carry out the deposition, and the filter cake was washed 5−7 times with nitric acid (1:100) for iron removal. To verify the completeness of the laundering of iron sludge from 0.5−1 cmflowing wash liquid is collected in a test tube and pour 3−5 drops of ammonium Rodenstock. The liquid in the vial should remain colorless.

The filter cake is washed with solution of nitrate of potassium for the removal of nitric acid. To verify the completeness of the laundering of sediment 2−3 cmof the filtrate taken in a test tube, add two drops of solution of phenolphthalein and one drop of sodium hydroxide solution. If the precipitate is washed, the solution in the vial should be painted in pink color.

The filtrate is discarded. The filter with precipitate was placed in a flask in which to carry out the deposition, poured 25 cmneutral water, five drops of phenolphthalein break the filter glass rod into smaller pieces and the contents of the flask stirred. Poured from a burette a standard solution of sodium hydrocide before the appearance of stable pink color of the solution and in excess of 3−5 cm, cover the flask with a rubber stopper and the contents shaken until complete dissolution of the precipitate. Tube removed, rinsed it and walls neutral with water and titrate the excess sodium hydroxide with a standard solution of nitric acid until the disappearance of the pink color.

Simultaneously conduct control experience on the phosphorus content in the reagents. To the filter with the sediment control experience, poured 25 cmneutral water, 25 cmof a standard solution of sodium hydroxide after dissolution of the precipitate octarepeat excess of sodium hydroxide standard solution with nitric acid as

described above.

3.4. Processing of the results

3.4.1. Mass fraction of phosphorus in percent is calculated by the formula

,

where is the volume of sodium hydroxide solution, taken in excess to dissolve the precipitate phosphoromolybdate ammonium, cm;

 — the volume of nitric acid consumed in the titration of excess sodium hydroxide by the volume consumed for titration of the solution in the reference experiment, cm;

 — mass concentration of the sodium hydroxide solution, expressed in grams of phosphorus;

 — the ratio between the standard solutions of sodium hydroxide and nitric acid;

 — weight of sample, g

.

3.4.2. Norms of accuracy and norms control the accuracy of determining the mass fraction of phosphorus are given in table.1.

4. GRAVIMETRIC METHOD

4.1. The essence of the method

The method is based on dissolving the sample in a mixture of nitric and hydrochloric acids, the excretion of phosphorus in the form of phosphoromolybdate ammonium, dissolving the precipitate in ammonia, the allocation of molybdate of lead, and weighing the calcined residue and terms of fraction of total mass of phosphorus.

4.2. Reagents and solutions

Nitric acid GOST 4461−77 and diluted 1:1 and 2:3.

Hydrochloric acid by the GOST 3118−77 and diluted 1:1, 1:2, 5:95 and 2:98.

Acid chloride with a density of 1.54 g/cm.

Hydrofluoric acid according to GOST 10484−78.

Sodium carbonate according to GOST 83−79.

Ammonium radamisty, a solution of 50 g/DM.

Iron chloride according to GOST 4147−74, a solution of 100 g/DM.

Ammonia water according to GOST 3760−79 diluted 1:2 and 5:95.

Acid bromatologica, density of 1.49 g/cm.

Potassium permanganate according to GOST 20490−75, a solution of 40 g/DM.

Sodium atomistically according to GOST 4197−74, a solution of 300 g/DM.

Potassium nitrate according to GOST 4217−77, a solution of 30 g/DM.

Hydroxylamine sulfate according to GOST 7298−79, or hydroxylamine hydrochloride according to GOST 5456−79, a solution of 100 g/DM.

Ammonium molybdate according to GOST 3765−78, solution: 300 g encoresarah ammonium molybdate dissolved in 2 DMwater and while stirring, pour a thin stream in a 2-DMsolution of nitric acid (1:1). Add 1 g of ammonium phosphate, mixed and after 24 h the precipitate is filtered off.

Irrigation solution: 20 cmof nitric acid solution is poured into 980 cmwater, add 50 g of ammonium nitrate, stirred and filtered.

Ammonium acetate according to GOST 3117−78, a solution of 250 g/DM.

Lead acetate according to GOST 1027−67, a solution of 40 g/DM.

Ammonium chloride according to GOST 3773−72.

The ammonium phosphate.

The sulfide from the device

and Kippa.

4.3. Analysis

4.3.1. Depending on the mass fraction of phosphorus take a charge in the amount indicated in the table.4.

Table 4

4.3.1.1. Analysis of iron with a mass fraction of phosphorus in excess of specified in tab.4, is performed on parts of a solution with a lower charge.

4.3.2. Cast iron and steel with a mass fraction of titanium, zirconium, tungsten, arsenic, and molybdenum is not more than 0.1%

A portion of steel or iron is dissolved, warming slightly to 15 cmof nitric acid (1:1) and 30 cmof hydrochloric acid in a beaker with a capacity of 400 cm. After dissolution, the sample solution was evaporated to dryness.

After cooling, the residue is dissolved in 15 cmof hydrochloric acid, evaporated to dryness and dried at a temperature of 130−135 °C to remove hydrochloric acid and the conversion of silicic acid in the insoluble state. If the dissolution is not decomposed carbides and the alloy contains more than 0.5% silicon, add 10−15 cmof perchloric acid, cover glass and evaporated to a dense vapour. To the residue add 20 cmof hydrochloric acid, 80 cmof hot water and heated to dissolve the salts.

The beaker content was filtered through filter paper mass of precipitate was washed 4−5 times with hot hydrochloric acid solution (5:95), and then 3−4 times with hot water. Filter the precipitate discarded. To the filtrate is added 20 cmof nitric acid and evaporated to the minimum volume, while avoiding salt extraction.

The evaporation with nitric acid was repeated once more. Then add 15 cmof nitric acid, 80 cmof hot water and leave for further progress in the anal

iza.

4.3.3. Cast iron and steel with a mass fraction of titanium, niobium and zirconium than 0.1%

The weight of steel or cast iron dissolve and prepare a slurry as specified in claim 4.3.2. The precipitate was filtered off, dried, incinerated and calcined in a platinum crucible at a temperature of 500−550 °C. In the pot pour 2−3 cmof nitric acid (1:1), 5−10 cmof a solution of hydrofluoric acid, carefully evaporated to dryness and gently ignited. The residue in the crucible is fused with 2−3 g of sodium carbonate and leached m 80 cmof hot water in a glass with a capacity of 100−150 cm. Removed from a glass crucible and rinsed with water, the solution is heated at a temperature of 70−80 °C for 15 min, then filtered off the precipitate through the filter paper mass and washed several times with hot water. The filter is discarded and the filtrate was attached to the main solution, add 20 cmof nitric acid and evaporated to the minimum volume, while avoiding salt extraction. The evaporation with nitric acid was repeated once more. Then topped up with 15 cmof nitric acid, 80 cmof hot water and leave for a further course of analysis

.

4.3.4. Iron and steel containing tungsten

The weight of steel or cast iron dissolve and prepare a slurry as specified in claim 4.3.2 until the transfer of silicic acid in the insoluble state.

To the dry residue is poured 20 cmof hydrochloric acid, 80 cmof hot water and heated to dissolve the salts. The contents of the crucible was filtered through a filter paper mass of precipitate was washed 4−5 times with hot hydrochloric acid solution (5:95) and then again 3−4 times with hot water. The solution is poured 20 cmof nitric acid and evaporated to the minimum volume, while avoiding salt extraction.

The operation is repeated again, then topped up with 15 cmof nitric acid, 80 cmof hot water, heated to dissolve the salts and leave. The allocation of the precipitate tungsten acid it is filtered off and washed as described above. Connect precipitation, burned in a platinum crucible, calcined and remove the silica as described in section 4.3.3. The residue in the crucible is fused with 3−5 g of sodium carbonate, the melt leached 80 cmof hot water in a glass with a capacity of 250 cm. The clear solution acidified with nitric acid until yellow Muti, add 2cmof a solution of ferric chloride and 10−15 cmof ammonia. The contents of the beaker are heated to boiling, filtered off the precipitate of iron hydroxide and iron phosphate and washed 2−3 times with hot solution of ammonia (5:95).

The filter cake is dissolved in 10−15 cmof hot nitric acid (2:3). The filter is washed several times with hot water, the resulting solution is attached to the main filtrate and is left for further course anal

iza.

4.3.5. Cast iron and steel with a mass fraction of arsenic higher than 0.05%

A portion of steel or iron is dissolved, warming slightly to 15 cmof nitric acid (1:1) and 30 cmof hydrochloric acid in a beaker with a capacity of 400 cm. After dissolution of the sample solution is evaporated to dryness, cool, moisten the residue with 15 cmof hydrochloric acid, then evaporated to dryness and dried at a temperature of 130−135 °C for the conversion of silicic acid in the insoluble state. After cooling in a glass pour 50 cmof a hydrochloric acid solution (1:2) and heated to dissolve the salts. The solution was added 30−40 cmbromatological acid and evaporated to dryness. Evaporation from bromatological acid repeat, adding pre-30−40 cmof hydrochloric acid. The solution was evaporated until the appearance of salts, add 10 cmof hydrochloric acid and diluted with 50 cmof hot water, heated to dissolve the salts and filtered. The residue of silica and graphite is washed on the filter with hydrochloric acid (2:98), to the filtrate add 20 cmof nitric acid and evaporated to the minimum volume, while avoiding salt extraction.

Repeat the evaporation with nitric acid, then add 15 cmof the same acid, 80 cmof hot water and leave the solution for the future course of an

Aliza.

4.3.6. Cast iron and steel with a mass fraction of molybdenum in excess of 1%

A portion of steel or iron is dissolved and then cooled as described in section 4.3.2 prior to the removal of silica. If necessary, the solution was evaporated to a volume of about 200 cm, neutralized with ammonia until the solution is kept Muti and add excess of 10 cm.

Through the heated solution for 30 min flow hydrogen sulfide. Received thiomolybdate ammonium decomposes, acidifying a slight excess of hydrochloric acid solution (1:1). To defend and filter selected molybdenum sulfide, and then washed with hydrochloric acid solution (2:98) until the termination of allocation of hydrogen sulfide. The filter is discarded and the filtrate is evaporated to minimum volume, while avoiding salt extraction. Then add 20 cmof nitric acid and repeat the evaporation. This operation is carried out two times. Then to the residue add 15 cmof nitric acid, 80 cmof hot water and leave for further progress analysis.

4.3.7. The oxidation of phosphorus to phosphoric acid and deposition of sediment phosphoromolybdate ammonium

To the solution obtained using one of the methods described in section 4.3.2, placed in a conical flask with a capacity of 300 cmand heated almost to the boiling point, add the potassium permanganate solution in an amount necessary for obtaining an intense pink color (at least 5 cm). The contents of the flask is boiled to release the brown hydrated oxide of manganese, and continuing the heating, added dropwise a solution of sodium nitrite to dissolve the solids and obtain a clear solution.

The solution was evaporated to a volume of about 40 cm, cooled, poured cautiously ammonia to the deposition of stable sediment of ferric hydroxide, the precipitate is dissolved by adding a few drops of nitric acid, and then poured the excess 5 cmof the same acid, 15 g of ammonium nitrate and stirred the contents of the flask to dissolve the reagent. In the case of the presence in the sample of vanadium, the solution was cooled to room temperature, add 15 cmof a solution of sulphate of hydroxylamine or hydrochloric acid for the recovery of pentavalent vanadium to tetravalent and stirring, is heated to a temperature of 50−60 °C and allowed to stand for 1 min.

Then add another 5 cmof the reagent and cooling of the solution, add 50 cmof ammonium molybdate solution, shaking for 2−3 min in a flask closed with a rubber stopper. The solution is allowed to stand in a water bath at a temperature of 30−35 °C for 2−3 h. the Solution samples that do not contain vanadium, are heated to a temperature of 50−60 °C and precipitated phosphorus as described above. The contents of the flask cooled, the precipitate was filtered off through a medium density filter and washed on the filter with a solution of 6−7 times for washing, checking for the absence of iron ion (drip test with radamisty ammonium), then washed several times with a solution of potassium nitrate

.

4.3.8. Phosphoromolybdate dissolution of the precipitate in ammonia and the precipitation of solution of molybdenum in the form of molybdate of lead

The filtered and washed precipitate phosphoromolybdate ammonium is dissolved on the filter in 15 cmhot solution of ammonia (1:2), adding it in chunks of 3−4 cm. The filtrate collected in a beaker with a capacity of 400 cm. The filter was washed 2−3 times with portions of 5 cmof hot water. The filtrate is heated to boiling. At the same time in another beaker with a capacity of 250 cm50 cm heatof solution of acetate of ammonium, to which is added 10 g of ammonium chloride. Since the beginning of boiling to the solution containing phosphoromolybdate, add 5−7 cmof hydrochloric acid, 10 cmof a solution of acetate of lead and poured into a boiling solution of ammonium acetate, rinsing the beaker 2−3 times with hot water, infusing the water after washing the glass with ammonium acetate.

The precipitate of lead molybdate is kept in a warm place for 20−30 minutes, then filter through a small ashless filter paper mass and washed with water to negative reaction on the ion of lead (control of paper saturated potassium iodide).

The washed precipitate together with the filter placed in a weighted porcelain crucible, carefully dried, and then the crucible is placed in an electric muffle and calcined precipitate at a temperature not higher than 650 °C for 25−30 min to constant weight. After cooling in the desiccator the crucible with the residue is weighed

T.

4.4. Processing of the results

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

,

where is the mass of the precipitate of lead molybdate in the sample, g;

 — the mass of the precipitate of lead molybdate in the control sample, g;

0,00704 — the ratio of the mass of phosphorus corresponding to 1 g of molybdate of lead;

 — the weight of the portion,

4.4.2. Norms of accuracy and norms control the accuracy of determining the mass fraction of phosphorus are given in table.1.