Enacted by the decision of the Committee Russian Federation on standardization, metrology and certification of March 21, 1996 N 196
Interstate standard GOST 14048.1-93
"ZINC CONCENTRATES. METHOD FOR THE DETERMINATION OF ZINC"
Zinc concentrates. Method for determination of zinc
Instead of GOST 14048.1-71
1 area of use
This standard applies to zinc concentrates and establishes a complexometric method for the determination of zinc at a mass fraction from 20 to 67%.
2 Essence of the method
The method is based on the titration of zinc with Trilon B at pH 5.6 - 5.8 in the presence of the xylenol orange indicator.
Interfering with the determination of lead, iron, manganese, aluminum is previously separated from zinc by precipitation of their sparingly soluble compounds (lead sulfate, hydroxides of iron, manganese, aluminum); copper, cadmium and traces of aluminum are masked with complexing agents (copper - sodium thiosulfate, cadmium - potassium iodide, traces of aluminum - ammonium fluoride).
3 Normative references
GOST 8.315-91 GSI. Standard samples. Basic provisions, procedure for development, certification, approval, registration and application
GOST 61-75 Acetic acid. Specifications
GOST 3117-78 Acetic ammonium. Specifications
GOST 3118-77 Hydrochloric acid. Specifications
GOST 3640-79 Zinc. Specifications
GOST 3760-79 Water ammonia. Specifications
GOST 3769-78 Ammonium sulfate. Specifications
GOST 3773-72 Ammonium chloride. Specifications
GOST 4204-77 Sulfuric acid. Specifications
GOST 4232-74 Potassium iodide. Specifications
GOST 4461-77 Nitric acid. Specifications
GOST 4518-75 Ammonium fluoride. Specifications
GOST 10652-73 Disodium salt of ethylenediamine -N, N, N`, N`-tetraacetic acid. specifications
GOST 10929-76 Hydrogen peroxide. Specifications
GOST 20478-75 Ammonium persulphate. Specifications
GOST 22867 Ammonium nitrate. Specifications
GOST 25363 Zinc concentrates. Atomic absorption methods for the determination of gold and silver
GOST 27067-86 Ammonium thiocyanate. Specifications
GOST 27068-86 Sodium sulphate (sodium thiosulfate) 5-aqueous. Specifications
GOST 27329-87 Ores and concentrates of non-ferrous metals. General requirements to methods of chemical analysis
4 General requirements
4.1 General requirements for the method of analysis - according to GOST 27329.
4.2 The mass fraction of zinc is determined in parallel on two test portions. The arithmetic mean of the results of parallel determinations is taken as the result of the analysis.
4.3 The accuracy of the analysis is controlled by standard samples of the zinc concentrate composition (state (GSO), industry (OSO), or enterprise standard (SOP)), developed and approved in accordance with GOST 8.315 or by the addition method at least once a month, as well as when changing reagents, solutions, after a long break in work.
4.4 The accuracy of the analysis of standard samples is controlled by analyzing the standard sample simultaneously with the analysis of samples. Sample analysis is considered accurate if the result of the analysis of a standard sample differs from the certified characteristic by no more than
where ∆ at - error of standard sample certification;
D - allowable discrepancy between the results of the analysis.
4.5 The accuracy of the analysis by the addition method is controlled by the mass fraction of zinc in the concentrate after addition to the sample before analysis of an aliquot of the zinc standard solution.
The additive (the volume of the standard solution) is chosen so that it is 30 - 100% of the zinc content in the sample.
The found additive is calculated as the difference between the zinc content in the sample with the additive (C P + D) and the results of the analysis of the sample (C P).
Sample analysis is considered accurate if the found value differs from its entered value by no more than
,
where D 1 and D 2 - allowable discrepancies between the two results of the analysis for the sample and the sample with the additive, respectively.
5 Safety requirements
Safety requirements - according to GOST 25363.
6 Apparatus, reagents and solutions
pH meter-millivoltmeter or ion meter of any type with a measurement accuracy of at least ±0.05 units. pH.
Nitric acid according to GOST 4461.
Hydrochloric acid according to GOST 3118 and diluted 1:1.
Sulfuric acid according to GOST 4204, diluted 1:1 and 2:100.
Acetic acid according to GOST 61.
Water ammonia according to GOST 3760 and diluted 1:1.
Ammonium nitrate according to GOST 22867.
Ammonium persulphate according to GOST 20478.
Ammonium thiocyanate according to GOST 27067, solution with a mass fraction of 2%.
Ammonium sulfate according to GOST 3769.
Ammonium acetate according to GOST 3117.
Ammonium fluoride according to GOST 4518, solution with a mass fraction of 20%.
Ammonium chloride according to GOST 3773, solution with a mass fraction of 2%.
Hydrogen peroxide according to GOST 10929.
Potassium iodide according to GOST 4232.
Sodium sulphate (sodium thiosulfate) 5-water according to GOST 27068, solution with a mass fraction of 20%.
Buffer solution pH 5, 7 ± 0, 1: acetic or hydrochloric acid is added to a solution of ammonium acetate with a mass fraction of 20% to pH 5, 6 - 5, 8; The pH of the solution is checked with a pH meter.
Xylenol orange, indicator - according to ND, solution with a mass fraction of 0.5%.
Zinc not lower than grade Ts1 according to GOST 3640 or granulated zinc according to ND.
Disodium salt of ethylenediamine -N, N, N ", N "-tetraacetic acid, 2-aqueous (trilon B) according to GOST 10652, solution 0.08 mol / dm 3: 29.6 g of salt is dissolved in water; if the solution is cloudy, it is filtered, diluted with water to 1 dm 3 and stirred.
To set the titer of the solution, a weighed portion of zinc weighing 0.1500 g is placed in a conical flask with a capacity of 500 cm 3, 15 cm 3 of hydrochloric acid diluted 1: 1 is added, and left in a warm place for 1-2 hours until the zinc is completely dissolved. The solution is diluted with water to 200 cm 3 , 8 g of ammonium sulphate, 10 cm 3 of ammonium fluoride solution, 5 cm 3 of sodium thiosulfate solution, 1-2 drops of xylenol orange solution are added. The solution is neutralized with ammonia diluted 1:1 until a pale pink color appears. If an excess of ammonia is accidentally added (crimson color of the solution), the solution is neutralized by dropwise addition of sulfuric acid (1:1) to a pale pink color. Add 30 - 40 cm 3 buffer solution with a pH of 5.6 - 5.8 and titrate zinc with a solution of Trilon B until the color changes from raspberry to lemon yellow.
The titer of a solution of Trilon B T for zinc in g / cm 3 is calculated by the formula
where m is the mass of the zinc sample, g;
V is the volume of Trilon B solution used for titration, cm3.
7 Analysis
A sample of a zinc concentrate weighing 0.5000 g with a zinc content of up to 40% or 0.3000 g - with a zinc content of over 40% is placed in a conical flask with a capacity of 250 cm 3, moistened with water, 15 cm 3 of hydrochloric acid are added and heated for 10 min. Add 5 cm 3 of nitric acid and continue heating until the rapid release of nitrogen oxides stops and the volume of the solution decreases to 3-5 cm 3 . Pour 10 cm 3 of a solution of sulfuric acid, diluted 1:1, and heat until the release of vapors of sulfuric acid. If the solution acquires a dark color due to the presence of organic substances, ammonium nitrate is added in small portions (20-50 mg each) or nitric acid carefully, drop by drop, until they are destroyed.
The solution is cooled, the walls of the flask are carefully washed with water, and the evaporation is repeated to the vapors of sulfuric acid.
The residue is cooled, 60 - 70 cm 3 of water are added, boiled for 5 - 10 minutes until soluble sulfates dissolve.
The solution is cooled in running water for 1 hour, then filtered through a swab of filter paper or a medium density filter containing filter paper into a 250 cm 3 conical flask. The swab (filter with sediment) is washed with sulfuric acid, diluted 2:100, until the wash water reacts negatively to iron with a solution of ammonium thiocyanate.
Ammonia is added to the filtrate until the precipitation of iron hydroxide, which dissolves with agitation, is added, 0.3-0.5 g of ammonium persulphate is added, the solution is brought to a boil, and boiled for 5-10 minutes, cooled slightly and ammonia is added again until the hydroxides are completely precipitated and excess 10 cm3. The solution with the precipitate is kept at 60 - 70°C for 10 - 15 min until coagulation of the precipitate and filtered through a loose filter into a conical flask with a capacity of 500 cm 3 .
The flask and the precipitate on the filter are washed two or three times with a hot solution of ammonium chloride, then the precipitate from the unfolded filter is washed off with water into the flask in which the hydroxides were precipitated, 3–5 cm 3 of sulfuric acid 1: 1, two or three drops of hydrogen peroxide and ammonia precipitation is repeated as described above.
The precipitate is filtered off on the same filter and washed two or three times with hot ammonium chloride solution, then five or six times with hot water.
Two or three pieces of filter paper are dipped into the combined filtrates (to avoid splashing) and boiled until the smell of ammonia is removed and the volume of the solution is reduced to 200 cm 3 .
The solution is cooled, 10 cm 3 of ammonium fluoride solution, 5-10 cm 3 of sodium thiosulfate solution, one or two drops of xylenol orange indicator, 30-40 cm 3 of buffer solution are added and zinc is titrated with Trilon B until the color changes from crimson red to yellow.
If the sample contains more than 0.3% cadmium, add 30-40 g of potassium iodide before adding the buffer solution.
8 Processing results
8.1 Mass fraction of zinc X, %, is calculated by the formula
,
where V is the volume of Trilon B solution used for titration, cm3;
T is the titer of Trilon B solution for zinc, g/cm 3 ;
m is the mass of the concentrate sample, g.
8.2 Calculate the result of the analysis to the third and round to the second decimal place.
8.3 The absolute values of the difference between the results of parallel determinations (d) and the results of two analyzes (D) at a confidence level P = 0.95 should not exceed the allowable discrepancies specified in Table 1.
Table 1 - Permissible differences
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In percentages |
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Mass fraction of zinc | ||
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From 20.00 to 25.00 inclusive | ||
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St. 25.00 "30.00" | ||
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" 30, 00 " 35, 00 " | ||
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" 35, 00 " 40, 00 " | ||
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" 40, 00 " 45, 00 " | ||
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" 45, 00 " 50, 00 " | ||
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" 50, 00 " 55, 00 " | ||
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" 55, 00 " 60, 00 " | ||
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" 60, 00 " 65, 00 " | ||
8.4 The analysis report should contain:
Data required to characterize the sample;
Description of any abnormalities observed during the analysis;
An indication of the performance in the analysis of any operations not covered by this standard.
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STATE STANDARD
UNION SSR
O.
USSR STANDARDIZATION AND METROLOGY COMMITTEE
STATE STANDARD
UNION SSR
COPPER-ZINC ALLOYS
METHODS FOR THE DETERMINATION OF ZINC
5. TITRIMETRIC COMPLEXONOMETRIC METHOD
5.1. Method Essence
The method is based on the complexometric titration of zinc in the presence of xylenol orange as an indicator after preliminary separation of copper and lead by electrolysis, manganese - in the form of manganese dioxide, iron - in the form of hydroxide, nickel - in the form of dimethylglyoximate, precipitated from the electrolyte simultaneously.
5.2. Equipment, reagents and solutions
Electrolysis plant with grid platinum electrodes according to GOST 6563.
Buffer solution pH=5.5-5.7:18 g of sodium acetate, 46 g of ammonium acetate and 20 cm 3 of acetic acid solution are dissolved in 1 dm 3 of water. Check and adjust the pH of the solution on a pH meter by adding acetic acid or ammonia.
GOST 10652, solution 0.05 mol / dm 3 (see preparation p. 2.2).
where m is the mass of zinc taken for titration, g;
V is the volume of Trilon B solution used for titration, cm3.
5.3. Conducting an analysis
A sample weighing 1 g is placed in a beaker with a capacity of 250 cm 3 , 15 cm 3 of nitric acid solution are added, covered with a watch glass and dissolved first without heating, and then when heated.
After dissolving the sample and removing nitrogen oxides, the glass and the walls of the glass are rinsed with water by boiling, the solution is diluted with water to 100-150 cm 3 (if the alloy contains tin, then it is filtered out), 7 cm 3 of a sulfuric acid solution are added and copper is isolated by electrolysis according to GOST 1652.1 . If the alloy contains more than 0.5% lead, then a sulfuric acid solution is added 25-30 minutes after the start of electrolysis.
The electrolyte, after separation of copper, is transferred to a 250 cm 3 volumetric flask, topped up to the mark with water and mixed.
An aliquot of the solution is taken - 50 cm 3 into a glass with a capacity of 250 cm 3, water is added 50 cm 3 and if the alloy contains more than 0.5% manganese, then it is neutralized with solutions of ammonia and sodium carbonate to pH = 3-4 according to universal indicator paper . The solution is heated almost to a boil, 10 cm 3 of a solution of ammonium persulphate are added to precipitate manganese in the form of manganese dioxide, the solution is boiled under a lid until ammonium persulphate is destroyed, and then the solution is cooled.
The solution is neutralized to pH = 5-6 with ammonia solution and give an excess of 3 cm 3 . Then the solution is heated to 60°C, 20 cm 3 of a dimethylglyoxime solution are added to precipitate nickel, and the solution with the precipitate is kept for 20-30 minutes in a dark place. The precipitate is filtered off on a medium-density filter, washed with ammonium chloride solution 8-10 times, collecting the filtrate in a beaker, in which Nickel was precipitated.
The filtrate is transferred to a volumetric flask with a capacity of 100 cm 3 to the mark, topped up with water and mixed.
An aliquot of the solution is placed in a conical flask with a capacity of 250 cm 3 (see Table 3), 1 cm 3 of tartaric acid solution, 5 cm 3 of sodium fluoride solution are added, and the solution is neutralized with ammonia solution on Congo paper to pH = 5. Then add 40 cm 3 of a buffer solution, 1 cm 3 of xylenol orange and the solution are titrated with Trilon B until the color of the solution changes from lilac to yellow.
5.4. Results processing
5.4.1. The mass fraction of zinc (X 3) as a percentage is calculated by the formula
T is the mass concentration of Trilon B solution for zinc, g/dm 3 ;
5.4.2. The discrepancies between the results of three parallel determinations should not exceed the values of the allowable discrepancies d (d is the convergence index) given in Table. 2.
5.4.3. The discrepancies between the results of the analysis obtained in two different laboratories or two results of the analysis obtained in the same laboratory, but under different conditions D (D - reproducibility index) should not exceed the values \u200b\u200bgiven in Table 2.
5.4.4. The accuracy of the analysis results is controlled according to the State standard samples of copper-zinc alloys, approved in accordance with GOST 8.315 GOST 25086.
COPPER AND COPPER ALLOYS ZINC DETERMINATION
Flame atomic absorption spectrometric method
1 area of use
Real international standard establishes a flame atomic absorption spectrometric method for determining the mass fraction of zinc in copper and copper alloys all types, except alloys containing more than 10% lead.
The method is applicable at a mass fraction of zinc from 0.001 to 6%.
Place (2*5±0,<Ш1) г металлического цинка (чистотой 99,99 %) в высокий стакан вместимостью 250 ом 3 . Добавляют 50 см 3 раствора азотной, кислоты (ГОСТ 44Ш-, разбавленной Ы) Л накрывают стакан крышкой и слегка нагревают до растворения мета"лла. Кипятят раствор в течение нескольких шнут до прекращения выделения паров окиси азота, затем охлаждают. Переливают раствор в мерную колбу вместимостью 5-00, см 3 , доливают до метки водой и перемешивают.
1 ml of this standard solution contains 5 mg of zinc.
4.4. Zinc, standard solution containing 0.5 g/dm 3 zinc nc a
Place IU.0 ml of zinc stock standard solution in a volumetric flask with a capacity of ! LLC cm 3. Dilute to the mark with water and mix.
1 ml of this standard solution contains 0.5 Mg of zinc.
4.5. Zinc, standard solution containing 0.06 g/dm 3 zinc
Place 10.0 cm 3 of the basic zinc standard solution in a volumetric flask with a capacity of CSO cm 3 . Dilute to the mark with water and mix.
1 ml of this standard solution contains 0.05 mg of zinc.
4.6. Zinc, standard solution containing 0.01 g/dm 3 zinc
Place 2.0 ml of zinc stock standard solution in a 1000 ml volumetric flask. Dilute to the mark with water and mix.
J eat 3 of this standard solution contains 0.0] mg of zinc.
5. Equipment
Conventional laboratory apparatus with the addition of:
5L. Teflon glasses with a capacity of 1000 and 25Q ohm 3.
5.2. Burettes with a division price of 0.05 cm 3.
5.5. Flame atomic absorption spectrometer. Hollow zinc cathode lamp or electrodeless discharge lamp,
5.4. Compressor for supplying compressed air.
5.5. Acetylene bottle.
6. Sampling
Sampling is carried out in accordance with the international standard ISO 18 Y. The metal should be predominantly in the form of drilling chips with a thickness of not more than 0.3 mm.
7. Analysis
7.1. Preparation of calibration solutions
7.4.1. Mass fraction of zinc from 0.001 to 0.01%
In four volumetric flasks with a capacity of 100 cm 3 place a standard solution of zinc with a concentration of 0.01 g/DM 3 and a background solution of copper in the amount indicated in table. 1. Dilute to the mark with water and mix.
Table 1
7.1.2. Mass fraction of zinc from 0.005 to 0.06%
In six volumetric flasks with a capacity of 200 cm 3 place a standard solution of zinc with a concentration of 0.06 g/DM 3 and a background solution of copper in the amount indicated in table. 2. Dilute to the mark with water and mix.
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table 2 |
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* Blank sample for calibration. |
7 1.3. Mass fraction of zinc from 0 L 05 to 0.00%
In six volumetric flasks with a capacity of 200 cm 3, a standard solution of zinc with a concentration of 0.5 g / dm 3 and a background solution of copper in the amount indicated in the table are placed. 3. Top up to the mark with water and mix. 1 GO cm 3 of the resulting solutions are placed in six volumetric flasks with a capacity> 1000 cm 3 each, each flask is topped up to the mark with water and mixed.
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Table 3 |
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* Blank sample for calibration. |
7.1.4. Mass fraction of zinc from 0.5 to 6%
In six volumetric flasks with a capacity of 200 cm 3 place a standard solution of zinc with a concentration of 5 g/DM 3 and a background solution of copper in the amount indicated in table. 4. Top up to the mark with water and mix. 10 cm 3 of the resulting solutions are placed in six volumetric flasks with a capacity of 1000 cm 3 each flask is topped up to the mark with water and mixed.
7.2. Preparation of solution for analysis
7.2.1. Place the sample for analysis (chips) weighing (1 ± 0.0002) g in a Teflon beaker. If heating is done in a water bath, beakers made of polypropylene or low density polyethylene can be used.
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Table 4 |
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beyond the 0.55 absorption limit of the calibration solution with the maximum zinc content If this situation occurs, the calibration solutions should be diluted to the min. zinc content necessary to obtain the optimal curvature. The analysis solutions should also be diluted in the same proportion
7 3 4 Measurement of solution for analysis
Measure the absorbance of the test solution and the blank in the same way as for the calibration solutions Compare the test solution with the two corresponding calibration solutions All measurements are made in tichtal? sequence and without interruptions to minimize instrumental error fluctuations
74 Blank Sample
A blank sample is produced simultaneously with the determination of the analyzed sample according to the same method, using the same amounts of reagents and copper as in the analysis, but without the sample being analyzed
75 Control measurement
A preliminary check of the equipment is carried out by preparing a solution of a standard material or a synthesized solution containing a known amount of zinc and having a composition similar to the composition of the analyzed material, and performing the operations ^ a d II> given in paragraphs 7 2 and 7 3
8. Processing of results
Using the appropriate calibration graph (p 7 3 3), determine the concentration of zinc ^ in solution from the measured absorbance
The mass fraction of zinc ^ in percent is calculated by the formula
(t 2 -m x) f V 1000 t 0
-<масса навески д ля анализа, г,
The mass of zinc, determined in a blank sample, mg,
The mass of zinc determined in the analyzed solution, mg; the ratio of the volume of the solution in the first flask to the volume poured into the second flask, f =\ t if the first flask contains the final test solution, i.e. the solution is not diluted, the volume of the flask containing the final test solution, cm 3
9. Analysis report
The analysis report must contain
a) Tsrob selection technique,
b) the method used, e analysis,
c) the results obtained and the method of their calculation,
d) all the characteristic features seen in the analysis,
e) all operations performed that are not covered by this International Standard, or are considered incidental
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of Metallurgy of the USSR DEVELOPERS
V. N. Fedorov, Yu. M. Leibov, B. P. Krasnov, A. N. Boganova, L. V. Moreiskaya, I. A. Vorobieva
2. APPROVED AND INTRODUCED \ INTO ACTION by the Decree of the Committee for Standardization and Metrology of the USSR dated 03.10.91 No. 158
3. The annex to this standard has been prepared by direct application of the international standard ISO 4740-85 “Copper and copper alloys. Determination of zinc. Flame atomic absorption spectrometric method»
5. REFERENCE REGULATIONS AND TECHNICAL DOCUMENTS
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Item number, section, application |
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2.2, 3.2, 4.2, 5.2 |
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2.2, 3.2, 4.2, 5.2 |
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2.2, 3.2, 4.2, 5.2, application |
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Sec. 1, 4.4, 5.4.4 |
UDC 669.35 "5: 5.OO1.4: O06.354 Group B59
STATE STANDARD OF THE UNION OF THE SSR
(ISO 4740-85)
COPPER-ZINC ALLOYS
Methods for the determination of zinc
Capper-zinc alloys. Methods for determination of zinc
Date of introduction from 01.01.93
This standard establishes titrimetric complexometric methods for the determination of zinc with a mass fraction of zinc from 3 to 45% and an atomic absorption method for the determination of zinc with a mass fraction of zinc from 3 to 10% in copper-zinc alloys according to GOST 15527 and GOST 17711.
It is allowed to carry out the determination of zinc in copper-zinc alloys according to the international standard ISO 4740-85, given in the appendix.
1. GENERAL REQUIREMENTS
General requirements for analysis methods - according to GOST 25086 with the addition: the arithmetic mean of three (two) parallel determinations is taken as the result of the analysis.
2. TITRIMETRIC COMPLEX-METRIC METHOD
2.1. Method Essence
The method is based on the dissolution of the alloy in a mixture of hydrochloric and nitric acids, the masking of interfering elements with thiourea, ammonium citrate and ammonium thiocyanate, the extraction of the zinc complex with methyl isobutyl ketone, the re-extraction into the aqueous phase, and the titration of zinc at pH 5.0-5.2 with a solution of Trilon B in the presence of xylenol orange.
Official edition
This standard cannot be reproduced, replicated and distributed without the permission of the State Standard of the USSR
2.2. Reagents and solutions
A mixture of masking reagents: 60 g of thiourea, 100 g of ammonium citrate and 150 g of ammonium thiocyanate are dissolved in 1 dm 3 of water.
Methyl Isobutyl Getone (MIBK).
Wash solution: 250 cm 3 of a solution of masking reagents are mixed in 250 cm 3 of water and 25 cm 3 of a hydrochloric acid solution diluted 1:4.
Xylenol orange, mixed with sodium chloride in a ratio of 1:100.
Hexamethylenetetramine (urotropine).
Zinc metal grade Ts0 according to GOST 3640.
Zinc standard solution; 1.0 g of zinc is dissolved in 10 cm3 of hydrochloric acid (1:1), transferred to a volumetric flask with a capacity of 1000 cm 3, added to the mark with water and mixed.
1 cm 3 solution contains 0.001 g of zinc.
Disodium salt of ethylenediamine-N, N, N", N "-tetraacetic acid, 2-aqueous (trilon B) according to GOST 10652, 0.05 mol / dm 3 solution: 18.61 g of trilon B is dissolved in water when heated, solution transfer to a volumetric flask with a capacity of 1000 cm 3, add water to the mark and mix.
2.3. Determination of mass concentration of Trilon B solution by zinc
50 cm 3 of a standard solution of zinc are placed in a separating funnel with a capacity of 250 cm 3 , ammonia is added dropwise until a persistent slight turbidity appears. Then add 50 cm 3 of hydrochloric acid (1:4), 50 cm 3 of the masking mixture solution and then proceed in accordance with paragraph 2.4.
The mass concentration of the solution, Trilon B (7), expressed in grams of zinc per 1 cm 3 of the solution, is calculated by the formula
where 0.05 is the mass of zinc taken for titration, g;
V is the volume of Trilon B solution used for titration, cm3.
2.4. Conducting an analysis
Depending on the mass fraction of zinc, a sample of the alloy (Table 1) is placed in a beaker with a capacity of 250 cm 3 and dissolved when heated in 25 cm 3 of a solution of a mixture of acids. After complete dissolution of the sample, the solution is boiled to remove nitrogen oxides. Then the solution is cooled, transferred into a volumetric flask with a capacity of 100 cm 3 , topped up to the mark with water and mixed.
An aliquot of the solution (Table 1) was placed in a separating funnel with a capacity of 250 cm 3 , topped up with water to 50 cm 3 and, with stirring, ammonia was added dropwise until a non-disappearing slight turbidity appeared. Then add 5 cm 3 of hydrochloric acid (1:1) and with thorough stirring add 70 cm 3 (with a mass fraction of zinc from 3 to 10%) or 50 cm 3 (with a mass fraction of zinc over 10%) of the masking mixture solution. Then 50 cm 3 of methyl isobutyl ketone are added and the mixture is shaken vigorously for 2 minutes. After separation of the phases, transfer the aqueous phase into a second separating funnel with a capacity of 250 cm 3 , add 20 cm 3 of methyl isobutyl ketone and repeat the extraction. After separation of the layers, the aqueous phase is drained and discarded, and the organic phase is added to the contents in the first separating funnel. The second separating funnel is rinsed with the combined extracts in the first separating funnel.
After phase separation, the aqueous phase is removed and the washed organic phase is placed in a beaker with a capacity of 400 cm 3 . The separating funnel is rinsed with 25 cm 3 of hydrochloric acid (1*4) followed by 100 cm 3 of water and both washings are added to the organic phase. Add 20 cm 3 ammonium fluoride solution, 20 cm 3 thiourea solution and mix thoroughly.
0.1 g of a mixture of xylene orange with sodium chloride is added at the tip of a spatula and hemotropin is introduced in small portions until a red-violet color of the aqueous phase appears and a pH of 0.5-5.2 is established according to the Rifan indicator paper and
titrate zinc with a solution of Trilon B while stirring both phases until the red-violet color of the aqueous phase changes to yellow. Before the end of the titration, the pH of the solution is controlled and, if necessary, urotropine or hydrochloric acid (1:4) is added to establish a pH of 5.0-5.2 and titrated by adding a solution of Trilon B dropwise with thorough mixing of both phases.
2.5. Results processing
2.5.1. The mass fraction of zinc (X) as a percentage is calculated by the formula
X= ■ 100,
where V is the volume of Trilon B solution used for titration, cm3;
T is the mass concentration of a solution of Trilon B, expressed in g of zinc, per 1 cm 3; pg is the weight of the sample corresponding to an aliquot of the sample solution, g.
2.5.2. The discrepancies between the results of three parallel determinations should not exceed the values of the allowable discrepancies d (d is the convergence index) given in Table. 2.
table 2
2.5.3. Differences in the results of the analysis obtained in two different laboratories, or two results of the analysis obtained in the same laboratory, but under different conditions D (D - reproducibility index) should not exceed the values given in table. 2.
2.5.4. The accuracy of the analysis results is controlled according to the State standard samples of copper-zinc alloys, approved in accordance with GOST 8.315, or by comparing the results obtained by the atomic absorption method, in accordance with GOST 25086.
3. ATOMIC ABSORPTION METHOD
3.1. Method Essence
The method is based on the dissolution of a weighed portion of the alloy in a mixture of hydrochloric and nitric acids and measurements of the atomic absorption of zinc in a d-Stylene-air flame at a wavelength of 213.8 nm.
3.2. Equipment, reagents and solutions
Atomic absorption spectrometer with radiation source
for zinc.
Hydrochloric acid according to GOST ZI8, diluted 1:1.
Zinc standard solutions
Solution A: Dissolve OD g of zinc in 30 cm 3 of hydrochloric acid, transfer to a volumetric flask with a capacity of 1000 cm 3, add water to the mark and mix.
1 cm 3 of solution A contains OD mg of zinc.
Solution B: 25 cm 3 of solution A are placed in a volumetric flask with a capacity of 250 cm 3, topped up to the mark with water and mixed.
1 cm 3 of solution B contains 0.01 mg of zinc.
3.3. Conducting an analysis
3.3.1. A portion of the alloy weighing 0.2 g is placed in a glass with a capacity of 250 cm 3 and dissolved in 30 cm 3 of a mixture of acids.
The solution is cooled, transferred to a volumetric flask with a capacity of 500 cm 3 , topped up to the mark with water and mixed.
In a volumetric flask with a capacity of 100 cm 3 place an aliquot of the solution - 5 cm 3 , add 2 cm 3 hydrochloric acid solution, add water to the mark and mix.
The atomic absorption of zinc in the test solution is measured in parallel with the calibration curve solution and the control test solution in an acetylene-air flame using radiation at a wavelength of 213.8 nm.
3.4. Construction of a calibration graph
In seven of the eight volumetric flasks with a capacity of 100 cm 3 place 2.0; 4.0; 6.0 and 8.0 cm 3 zinc standard solution B; 1.0; 1.5 and 2.0 cm 3 standard solution And zinc, which corresponds to 0.02; 0.04; 0.06; 0.08; 0.10; 0D5 and 0.20 mg zinc.
Pour 2 cm 3 of hydrochloric acid into all flasks, add water to the mark and mix. Measure the atomic absorption of zinc immediately before and after measuring the absorption of zinc in the analyzed solution.
3.5. Results processing
3.5.1. The mass fraction of zinc (Xi) as a percentage is calculated by the formula
x 1 \u003d L with l- with ^Y.loo,
where s! - concentration of zinc in the analyzed solution, found according to the calibration curve, g/cm 3 ; c 2 - concentration of zinc in the solution of the control experiment, found according to the calibration curve, g/cm 3 ;
V is the volume of the volumetric flask for preparing the final solution of the analyzed sample, cm 3;
m is the weight of the sample corresponding to an aliquot of the solution, g.
3.5.2. The discrepancies in the results of parallel determinations should not exceed the values of the allowable discrepancies d (d is the convergence indicator) given in Table. 2.
3.5.3. Differences in the results of the analysis obtained in two different laboratories, or two results of the analysis obtained in the same laboratory, but under different conditions D (D - reproducibility index) should not exceed the values given in table. 2.
3.5.4. The accuracy of the analysis results is controlled according to the State standard samples of copper-zinc alloys, approved in accordance with GOST 8.315, or by the addition method or by comparing the results obtained by the titrimetric "method, in accordance with GOST 25086.
4. TITRIMETRIC COMPLEXONOMECTRIC METHOD
4.1. Method Essence
The method is based on the complexometric titration of zinc in the presence of black chromogen as an indicator after the separation of copper with sodium thiosulfate and the binding of iron and nickel in the complex with an ammonia solution of dimethylglyoxime.
Indicator mixture: black chromogen is triturated well with sodium chloride in a ratio of 1:100.
Disodium salt of ethylenediamine-N, N, N 7, N "-tetraacetic acid, 2-aqueous (trilon B) according to GOST 10652, solutions of 0.025 and 0.01 mol / dm 3, prepared from fixanal or as follows: 9.305 g or 3 ,7224 g of Trilon B is dissolved in 500 cm 3 of water at
heated, transferred to a volumetric flask with a capacity of 1 dm 3 and topped up to the mark with water.
|
Table 3 |
25 cm 3 of ammonium chloride solution is added to the filtrate to keep zinc in solution, 2-3 drops of methyl red and the solution is neutralized with an ammonia solution of dimethylglyoxime until the color changes from red to yellow and another 5 cm 3 excess. Add 5-6 drops of potassium dichromate solution, indicator mixture to the solution and titrate with Trilon B (see Table 3) until the red-violet color changes to green.
4.4. Results processing
4.4.1. The mass fraction of zinc (X 2) as a percentage is calculated by the formula
where V is the volume of Trilon B solution used for titration, cm3;
T - mass concentration of Trilon B solution for zinc, g/cm 3 ;
m is the sample weight corresponding to an aliquot of the solution, g.
4.4.2. The discrepancies between the results of three parallel determinations should not exceed the values of the allowable discrepancies d (d is the convergence index) given in Table. 2.
4.4.3. The discrepancies between the results of the analysis obtained in two different laboratories or two results of the analysis obtained in the same laboratory, but under different conditions D (D - reproducibility indicator) should not exceed the values given in table. 2.
4.4.4. The control of the accuracy of the analysis results is carried out according to the State standard samples of copper-zinc alloys, approved by GOST 8.315, or by comparing the results obtained by the atomic absorption method, in accordance with GOST 25086.
Mining engineering. GOST 14048.1-93: Zinc concentrates. Method for determination of zinc. OKS: Mining and minerals, Ore minerals and their concentrates. GOSTs. zinc concentrates. Method for determination of zinc. class=text>
GOST 14048.1-93
zinc concentrates. Method for determination of zinc
GOST 14048.1-93
Group A39
INTERSTATE STANDARD
ZINC CONCENTRATES
Method for determination of zinc
Zinc concentrates. Method for determination of zinc
OKS 73.060*
OKSTU 1709
_______________
* In the index "National Standards" 2008 OKS 73.060.99. -
Database manufacturer's note.
Introduction date 1997-01-01
Foreword
1 DEVELOPED by the Eastern Research Mining and Metallurgical Institute of Non-Ferrous Metals (VNIITsvetmet)
INTRODUCED by the State Standard of the Republic of Kazakhstan
2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (report N 2 dated April 15, 1994)
Voted to accept:
3 By Resolution of the Committee of the Russian Federation for Standardization, Metrology and Certification dated March 21, 1996 N 196, the interstate standard GOST 14048.1-93 was put into effect directly as state standard Russian Federation since January 1, 1997
4 INSTEAD OF GOST 14048.1-71
1 AREA OF USE
1 AREA OF USE
This standard applies to zinc concentrates and establishes a complexometric method for the determination of zinc at a mass fraction from 20 to 67%.
2 ESSENCE OF THE METHOD
The method is based on the titration of zinc with Trilon B at pH 5.6-5.8 in the presence of xylenol orange indicator.
Interfering with the determination of lead, iron, manganese, aluminum is previously separated from zinc by precipitation of their sparingly soluble compounds (lead sulfate, hydroxides of iron, manganese, aluminum); copper, cadmium and traces of aluminum are masked with complexing agents (copper - sodium thiosulfate, cadmium - potassium iodide, traces of aluminum - ammonium fluoride).
3 REGULATORY REFERENCES
This standard uses references to the following standards:
GOST 8.315-91* GSI. Standard samples. Basic provisions, procedure for development, certification, approval, registration and application
______________
* On the territory of the Russian Federation, GOST 8.315-97 applies, hereinafter in the text. - Database manufacturer's note.
GOST 61-75 Acetic acid. Specifications
GOST 3117-78 Acetic ammonium. Specifications
GOST 3118-77 Hydrochloric acid. Specifications
GOST 3640-79* Zinc. Specifications
______________
* On the territory of the Russian Federation, GOST 3640-94 applies, hereinafter in the text. - Database manufacturer's note.
GOST 3760-79 Water ammonia. Specifications
GOST 3769-78 Ammonium sulfate. Specifications
GOST 3773-72 Ammonium chloride. Specifications
GOST 4204-77 Sulfuric acid. Specifications
GOST 4232-74 Potassium iodide. Specifications
GOST 4461-77 Nitric acid. Specifications
GOST 4518-75 Ammonium fluoride. Specifications
GOST 10652-73 Disodium salt of ethylenediamine - N,N,N",N"-tetraacetic acid. Specifications
GOST 10929-76 Hydrogen peroxide. Specifications
GOST 20478-75 Ammonium persulphate. Specifications
GOST 22867-77 Ammonium nitrate. Specifications
GOST 25363-82 Zinc concentrates. Atomic absorption methods for the determination of gold and silver
GOST 27067-86 Ammonium thiocyanate. Specifications
GOST 27068-86 Sodium sulphate (sodium thiosulfate) 5-aqueous. Specifications
GOST 27329-87 Ores and concentrates of non-ferrous metals. General requirements for methods of chemical analysis
4 GENERAL REQUIREMENTS
4.1 General requirements for the method of analysis - according to GOST 27329.
4.2 The mass fraction of zinc is determined in parallel on two test portions. The arithmetic mean of the results of parallel determinations is taken as the result of the analysis.
4.3 The accuracy of the analysis is controlled by standard samples of the zinc concentrate composition (state (GSO), industry (OSO), or enterprise standard (SOP)), developed and approved in accordance with GOST 8.315 or by the addition method at least once a month, as well as when changing reagents, solutions, after a long break in work.
4.4 The accuracy of the analysis of standard samples is controlled by analyzing the standard sample simultaneously with the analysis of samples. Sample analysis is considered accurate if the result of the analysis of a standard sample differs from the certified characteristic by no more than
where is the standard sample certification error;
- allowable discrepancy between the results of the analysis.
4.5 The accuracy of the analysis by the addition method is controlled by the mass fraction of zinc in the concentrate after addition to the sample before analysis of an aliquot of the zinc standard solution.
The additive (the volume of the standard solution) is chosen so that it is 30-100% of the zinc content in the sample.
The found additive is calculated as the difference between the zinc content in the sample with the additive () and the results of the sample analysis ().
Sample analysis is considered accurate if the found value differs from its entered value by no more than
where and are the allowable discrepancies between the two analysis results for the sample and the sample with the additive, respectively.
5 SAFETY REQUIREMENTS
Safety requirements - according to GOST 25363.
6 APPARATUS, REAGENTS AND SOLUTIONS
pH meter-millivoltmeter or ion meter of any type with a measurement accuracy of at least ±0.05 units. pH.
Nitric acid according to GOST 4461.
Hydrochloric acid according to GOST 3118 and diluted 1:1.
Sulfuric acid according to GOST 4204, diluted 1:1 and 2:100.
Acetic acid according to GOST 61.
Water ammonia according to GOST 3760 and diluted 1:1.
Ammonium nitrate according to GOST 22867.
Ammonium persulphate according to GOST 20478.
Ammonium thiocyanate according to GOST 27067, solution with a mass fraction of 2%.
Ammonium sulfate according to GOST 3769.
Ammonium acetate according to GOST 3117.
Ammonium fluoride according to GOST 4518, solution with a mass fraction of 20%.
Ammonium chloride according to GOST 3773, solution with a mass fraction of 2%.
Hydrogen peroxide according to GOST 10929.
Potassium iodide according to GOST 4232.
Sodium sulphate (sodium thiosulfate) 5-water according to GOST 27068, solution with a mass fraction of 20%.
Buffer solution pH 5.7 ± 0.1: acetic or hydrochloric acid is added to a solution of ammonium acetate with a mass fraction of 20% to pH 5.6-5.8; The pH of the solution is checked with a pH meter.
Xylenol orange, indicator - according to ND, solution with a mass fraction of 0.5%.
Zinc not lower than grade Ts1 according to GOST 3640 or granulated zinc according to ND.
Ethylenediamine disodium salt - N,N,N",N"-tetraxyc acid, 2-aqueous (trilon B) according to GOST 10652, solution 0.08 mol / dm: 29.6 g of the salt is dissolved in water; if the solution is cloudy, it is filtered, diluted with water to 1 dm and stirred.
To set the titer of the solution, a weighed portion of zinc weighing 0.1500 g is placed in a conical flask with a capacity of 500 cm3, 15 cm3 of hydrochloric acid diluted 1:1 is added, and left in a warm place for 1-2 hours until the zinc is completely dissolved. The solution is diluted with water to 200 ml, 8 g of ammonium sulphate, 10 ml of ammonium fluoride solution, 5 ml of sodium thiosulfate solution, 1-2 drops of xylenol orange solution are added. The solution is neutralized with ammonia diluted 1:1 until a pale pink color appears. If an excess of ammonia is accidentally added (crimson color of the solution), the solution is neutralized by dropwise addition of sulfuric acid (1:1) to a pale pink color. Add 30-40 ml of a buffer solution with a pH of 5.6-5.8 and titrate zinc with a solution of Trilon B until the color changes from raspberry to lemon yellow.
The titer of Trilon B solution for zinc in g/cm is calculated by the formula
where is the mass of the zinc sample, g;
- volume of Trilon B solution used for titration, see
7 CONDUCTING THE ANALYSIS
A sample of zinc concentrate weighing 0.5000 g with a zinc content of up to 40% or 0.3000 g - with a zinc content of more than 40% is placed in a conical flask with a capacity of 250 cm3, moistened with water, 15 cm3 of hydrochloric acid is added and heated for 10 minutes. Add 5 cm 3 of nitric acid and continue to heat until the rapid evolution of nitrogen oxides stops and the volume of the solution decreases to 3-5 cm. If the solution becomes dark in color due to the presence of organic substances, ammonium nitrate is added in small portions (20-50 mg each) or nitric acid carefully, drop by drop, until they are destroyed.
The solution is cooled, the walls of the flask are carefully washed with water, and the evaporation is repeated to the vapors of sulfuric acid.
The residue is cooled, 60-70 cm3 of water is added, boiled for 5-10 minutes until soluble sulfates dissolve.
The solution is cooled in running water for 1 hour, then filtered through a swab of filter paper or a medium-density filter containing filter paper into a 250 ml conical flask. The swab (filter with a precipitate) is washed with sulfuric acid diluted 2:100 to negative reactions of washing waters for iron with ammonium thiocyanate solution.
Ammonia is added to the filtrate until the precipitation of iron hydroxide, which dissolves with agitation, is added, 0.3-0.5 g of ammonium persulphate is added, the solution is brought to a boil and boiled for 5-10 minutes, slightly cooled and ammonia is added again until the hydroxides are completely precipitated and an excess of 10 cm. The solution with a precipitate is kept at 60-70 ° C for 10-15 minutes until the precipitate coagulates and is filtered through a loose filter into a conical flask with a capacity of 500 ml.
The flask and the precipitate on the filter are washed two or three times with a hot solution of ammonium chloride, then the precipitate from the unfolded filter is washed off with water into the flask in which the hydroxides were precipitated, 3-5 cm3 of sulfuric acid 1:1, two or three drops of hydrogen peroxide are added and precipitation ammonia is repeated as described above.
The precipitate is filtered off on the same filter and washed two or three times with hot ammonium chloride solution, then five or six times with hot water.
Two or three pieces of filter paper are dipped into the combined filtrates (to avoid splashing) and boiled until the smell of ammonia is removed and the volume of the solution is reduced to 200 ml.
The solution is cooled, 10 ml of ammonium fluoride solution, 5-10 ml of sodium thiosulfate solution, one or two drops of xylenol orange indicator, 30-40 ml of buffer solution are added and zinc is titrated with Trilon B until the color changes from crimson red to yellow.
If the sample contains more than 0.3% cadmium, add 30-40 g of potassium iodide before adding the buffer solution.
8 PROCESSING THE RESULTS
8.1 Mass fraction of zinc,%, calculated by the formula
where is the volume of Trilon B solution used for titration, cm;
- titer of Trilon B solution for zinc, g/cm;
- weight of concentrate sample, g.
8.2 Calculate the result of the analysis to the third and round to the second decimal place.
8.3 The absolute values of the difference between the results of parallel determinations () and the results of two analyzes () at a confidence level of 0.95 should not exceed the allowable discrepancies indicated in Table 1.
Table 1 - Permissible differences
In percentages
Mass fraction of zinc | ||
From 20.00 to 25.00 incl. | ||
St. 25.00 "30.00" | ||
8.4 The analysis report should contain:
- data necessary to characterize the sample;
- the result of the analysis;
- a reference to this standard;
- a description of any abnormalities observed during the analysis;
- an indication of the conduct in the process of analysis of any operations that are not provided for by this standard.
GOST 20580.3-80*
(ST SEV 908-78)
Group B59
STATE STANDARD OF THE UNION OF THE SSR
LEAD
Method for determination of zinc
lead. Method for the determination of zinc
OKSTU 1709**
________________
** Revised edition, Rev. N 2.
Introduction date 1980-12-01
By the Decree of the USSR State Committee for Standards of April 29, 1980 N 1976, the validity period is set from 01.12.80
Checked in 1983. By Decree of the State Standard of December 20, 1983 N 6396, the validity period was extended until December 1, 1991 **
________________
** The limitation of the period of validity was removed according to protocol N 7-95 of the Interstate Council for Standardization, Metrology and Certification (IUS N 11, 1995). - Database manufacturer's note.
INSTEAD OF GOST 20580.3-75
* REPUBLICATION December 1984 with Amendment No. 1 approved in December 1983 (IUS 4-84)
INTRODUCED Amendment No. 2, approved and put into effect by the Decree of the State Standard of the USSR dated 17.07.90 N 2203 from 01.01.91
Change No. 2 was made by the database manufacturer according to the text of IUS No. 11, 1990
This International Standard specifies a polarographic method for the determination of zinc from 0.0005 to 0.1% in lead (99.992-99.5%).
The method is based on the dissolution of lead in nitric acid, its precipitation in the form of sulfate, and the polarography of zinc in an ammonia medium within potentials from minus 1.0 to minus 1.8 V relative to a saturated calomel electrode.
The standard fully complies with ST SEV 908-78.
1. GENERAL REQUIREMENTS
1.1. General requirements for the method of analysis and safety requirements - according to GOST 20580.0-80.
1.2. (Deleted, Rev. N 2).
2. APPARATUS, REAGENTS AND SOLUTIONS
Oscillographic polarograph or AC polarograph of any type.
Quartz flasks with a capacity of 250 cm according to GOST 19908-80*.
_______________
* GOST 19908-90 is valid. - Database manufacturer's note.
Nitric acid according to GOST 4461-77, diluted 1:3.
Sulfuric acid according to GOST 4204-77 and diluted 1:1 and 1:48.
Hydrochloric acid according to GOST 3118-77 and diluted 1:1.
Water ammonia according to GOST 3760-79.
Congo red.
Sodium sulfite (sodium sulfite) crystalline according to TU 6-09-5313-87, saturated solution.
Edible gelatin according to GOST 11293-78*, solution with a mass concentration of 10 g/dm3, freshly prepared.
_______________
* GOST 11293-89 is valid. - Database manufacturer's note.
Zinc according to GOST 3640-79*.
_______________
* GOST 3640-94 applies. - Database manufacturer's note.
Mercury according to GOST 4658-73.
Zinc standard solutions.
Solution A: Dissolve 1,000 g of zinc in 50 ml of hydrochloric acid (1:1) with heating, add 25 ml of water, mix, cool and transfer to a 1 liter volumetric flask. Dilute to the mark with water and mix.
1 ml of solution A contains 1 mg of zinc.
Solution B: 50 ml of solution A is transferred into a volumetric flask with a capacity of 500 ml, topped up to the mark with water and mixed.
1 ml of solution B contains 0.1 mg of zinc.
Graduation solutions: in six volumetric flasks with a capacity of 100 cm3 are taken with pipettes or microburette 0.6; 1.0; 2.0; 10.0; 20.0 and 30.0 cm3 of solution B, add 10 cm3 of sulfuric acid (1:1). The solutions are neutralized with aqueous ammonia according to Congo red and an excess of 10 cm3 is added. The solutions are cooled, 10 cm3 of a saturated sodium sulfite solution are added, 2 cm3 of gelatin each in the case of polarography on an oscillographic polarograph, topped up to the mark with water and mixed thoroughly.
The calibration solutions contain 0.6; 1.0; 2.0; 10.0; 20.0 and 30.0 mg of zinc in 1 dm.
The shelf life of calibration solutions is 7 days.
3. CONDUCTING THE ANALYSIS
A weighing of lead weighing 10.00 g is placed in a conical flask with a capacity of 250 cm3 and dissolved in 70-80 cm3 of nitric acid (1:3). The solution is boiled to remove nitrogen oxides, cooled and transferred to a volumetric flask with a capacity of 250 ml, then topped up to the mark with water and mixed thoroughly. Depending on the zinc content, an aliquot of the solution is taken into a flask with a capacity of 250 cm3, with a mass fraction of zinc from 0.0005 to 0.001% - 100 cm3, from 0.001 to 0.01% - 50 cm3, more than 0.01% - 10 cm3.
An aliquot of the solution is diluted with water to 100 ml, heated to 60-70 ° C and 5 ml of sulfuric acid solution (1: 1) is added dropwise. A solution with a precipitate of lead sulfate is heated to boiling and cooled in running water. The precipitate is filtered off on a dense blue ribbon filter, the flask and filter are washed with a solution of sulfuric acid (1:48).
The filtrate and washings are evaporated to a volume of 2-3 cm3. The walls of the flask are washed with water and evaporated again until sulfuric anhydride vapor appears.
The residue is cooled, 5-7 cm 3 of water are added, neutralized with ammonia according to Congo red, 2.5 cm 3 of ammonia are added in excess, cooled and quantitatively transferred into a volumetric flask with a capacity of 25 cm 3. Then 2.5 cm 3 of a saturated sodium sulfite solution, 0.5 cm gelatin solution in the case of polarography on an oscillographic polarograph, top up to the mark with water and mix thoroughly.
The lead solution is poured into the electrolyzer and polarography of zinc is carried out within the potential range from minus 1.0 to minus 1.8 V (relative to the saturated calomel electrode), the mercury dripping rate is 5-6 s, the delay is 4-5 s, the voltage rate is 0, 25-0.5 V / s according to the scheme of the device "differential 1-3", on the device PO-5122. Zinc polarography using other devices is carried out at the optimum operating mode.
Simultaneously with the lead solution, polarography of calibration and control solutions is carried out. To calculate the results of the analysis, calibration solutions are used that are close in wave height to those under test. The addition method is allowed.
(Changed edition, Rev. N 2).
4. PROCESSING THE RESULTS
4.1. The mass fraction of zinc in percent is calculated by the formula
,
where is the wave height of the solution of the analyzed sample, mm;
Zinc concentration in the calibration solution, mg/dm;
The volume of the analyzed sample solution, cm;
Wave height of the calibration solution, mm;
Mass of the sample sample in the aliquot part, g
(Changed edition, Rev. N 1, 2).
4.2. The absolute allowable discrepancies between the results of parallel determinations and the results of the analysis should not exceed the values given in the table.
|
Mass fraction of zinc, % |
Permissible discrepancies in parallel definitions, % |
Permissible discrepancies in the analysis results, % |
|
From 0.0005 to 0.0010 inclusive |
||
|
St. 0.0010 "0.0020" |
||
|
" 0,0020 " 0,0050 " |
||
|
" 0,0050 " 0,0100 " |
||
|
" 0,010 " 0,040 " |
||
|
" 0,040 " 0,100 " |
(Changed edition, Rev. N 1, 2).
Electronic text of the document
prepared by CJSC and verified by:
official publication
Lead. Methods of chemical analysis.
GOST 20580.0-80-GOST 20580.12-80
(ST SEV 905-78-ST SEV 913-78): Sat. GOSTs. -
M.: Publishing house of standards, 1985
GOST 27996-88
Group C19
INTERSTATE STANDARD
VEGETABLE FEED
Methods for the determination of zinc
vegetable feeds. Methods for determination of zinc
OKSTU 9709
Introduction date 1990-01-01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the State Agro-Industrial Committee of the USSR
DEVELOPERS
S.G.Samokhvalov, Ph.D. s.-x. sciences (topic leader); N.A. Chebotareva, Ph.D. biol. sciences; G.I. Gorshkova; V.A. Chuikov, Ph.D. biol. sciences; H.K. Khudyakova, Ph.D. biol. Sciences
2. APPROVED AND INTRODUCED BY Decree of the USSR State Committee for Standards dated 12/23/88 N 4538
3. INTRODUCED FOR THE FIRST TIME
4. REFERENCE REGULATIONS AND TECHNICAL DOCUMENTS
Section number, paragraph |
|
GOST 61-75 | |
GOST 199-78 | |
GOST 1721-85 | |
GOST 1722-85 | |
GOST 1770-74 | 2.1.2; 3.1.2 |
GOST 3118-77 | 2.1.1; 2.1.2; 3.1.2 |
GOST 3760-79 | |
GOST 4204-77 | |
GOST 4453-74 | |
GOST 5457-75 | |
GOST 7194-81 | |
GOST 9147-80 | |
GOST 12026-76 | |
GOST 13586.3-83 | |
GOST 13979.0-86 | |
GOST 20288-74 | |
GOST 24104-88 | 2.1.1; 3.1.2 |
GOST 25336-82 | 2.1.1; 3.1.2 |
GOST 27068-86 | |
GOST 27262-87 | |
GOST 30692-2000 | Introduction |
5. The limitation of the validity period was removed according to protocol N 4-93 of the Interstate Council for Standardization, Metrology and Certification (IUS 4-94)
6. RE-ISSUE
This standard applies to foods of plant origin and establishes atomic absorption * and photometric methods for determining the mass fraction of zinc in them.
_______________
* According to GOST 30692.
1. SAMPLING
1. SAMPLING
Sampling - according to GOST 1721, GOST 1722, GOST 7194, GOST 13586.3, GOST 13979.0, GOST 27262.
2. ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF ZINC
The method is based on a comparison of the absorption of resonant radiation by free zinc atoms formed in a flame when solutions of feed ash and reference solutions with a known zinc concentration are introduced into it.
2.1. Equipment, materials and reagents
2.1.1. To prepare samples for testing and their mineralization, the following is used:
plant sample grinder IPR-2, straw cutter;
feed sample dryer SK-1 or a laboratory drying cabinet with a temperature maintenance error of not more than 5 °C;
laboratory mill MRP-2;
a sieve with round holes with a diameter of 1 mm, made of steel or aluminum;
porcelain mortar and pestle;
laboratory scales of the 2nd accuracy class with the highest weighing limit of 200 g according to GOST 24104*;
_______________
* Since July 1, 2002, GOST 24104-2001 has been put into effect (hereinafter).
a muffle furnace that maintains a temperature of 525 °C with an error of no more than 25 °C;
muffle tongs for crucibles;
water bath;
electric stove with heating regulator;
glass or plastic jars with a capacity of 250 cm3 with tightly closed stoppers or lids;
low porcelain crucibles N 4 according to GOST 9147;
watch glasses with a diameter of 5 cm;
melted laboratory glass sticks with a diameter of 36-56 mm according to GOST 25336;
graduated test tubes with a thin section with a capacity of 20 cm3 in accordance with GOST 25336;
stand for test tubes;
burettes with a tap of the 2nd accuracy class with a capacity of 50 cm3 or dispensers of aggressive liquids with a capacity of 2 and 5 cm3 with a dosing error of not more than 2%, made of materials that do not pollute the solution with zinc;
pipette of the 2nd class of accuracy with a capacity of 10 cm3;
hydrochloric acid according to GOST 3118, chemically pure, diluted with distilled water 1:1, 1:10 and 1:40 by volume;
distilled or deionized water; the suitability of water for analysis is checked as follows: on an electric stove in a glass with a capacity of 200-250 cm3, 500 cm3 of water is evaporated. 10 cm3 of hydrochloric acid, diluted 1:40, is added to the dry residue, mixed in a circular motion, trying to wash the walls of the glass, and analyzed according to clause 2.3.2 or 3.3.2. The mass concentration of zinc in the resulting solution should not exceed 0.2 μg / cm 3 (2 million in terms of the mass fraction in plant matter).
2.1.2. To determine zinc in ash solution, use:
atomic absorption spectrometer S-302, S-112 or S-115;
a lamp with a hollow cathode for the determination of zinc LSP-1 or LT-2;
membrane air compressor with a capacity of at least 20 dm3/min at a pressure of at least 300 kPa;
dissolved technical acetylene in accordance with GOST 5457 or household propane-butane in a cylinder;
volumetric flasks with ground stoppers of the 2nd accuracy class with a capacity of 50, 100 and 1000 cm 3 according to GOST 1770;
a burette with a tap of the 2nd accuracy class with a capacity of 10 cm3 and a pipette of the 2nd accuracy class with a capacity of 1 cm3;
hydrochloric acid according to GOST 3118, chemically pure, diluted with distilled water 1:1 and 1:40 by volume;
zinc granulated according to NTD, chemically pure
2.2. Preparing for the test
2.2.1. Sample preparation for testing
An average sample of hay, silage, haylage, straw, green fodder is crushed into segments 1-3 cm long; root crops are cut into plates (slices) up to 0.8 cm thick. By quartering, a part of the average sample is isolated, the mass of which after drying should be at least 100 g. Samples are dried in an oven at a temperature of 60-65 ° C to an air-dry state .
After drying, the air-dry sample is ground in a laboratory mill and sifted through a sieve. The residue on the sieve is crushed with scissors or in a mortar, added to the sifted part and mixed thoroughly.
The sample prepared for testing is stored in a glass or plastic jar with a lid in a dry place.
2.2.2. Preparation of a zinc solution with a mass concentration of 1 mg/cm (solution A)
1,000 g of granular zinc is dissolved in 7 cm 3 of hydrochloric acid diluted 1:1, the volume of the solution is adjusted to 1 dm with distilled water in a volumetric flask, mixed and stored in a bottle with a ground stopper for no more than 1 year.
2.2.3. Preparation of a zinc solution with a mass concentration of 20 µg/cm (solution B)
In a volumetric flask with a capacity of 50 ml, 1 ml of solution A is placed with a pipette, brought to the mark with hydrochloric acid diluted 1:40, and mixed. The solution is stored for no more than 3 months. It is allowed to prepare a mixed solution of zinc, copper, manganese, iron.
2.2.4. Preparation of reference solutions
In volumetric flasks with a capacity of 100 cm3 from a burette with a capacity of 10 cm3, the volumes of solution B indicated in Table 1 are poured, adjusted to the mark with hydrochloric acid diluted 1:40, and mixed thoroughly. Reference solutions are prepared on the day of the test. It is allowed to prepare mixed solutions of zinc, copper, manganese, iron.
Table 1
Reference solution number | Volume of solution B, cm | Mass concentration of zinc in the reference solution in terms of mass fraction in plant material ppm (mg/kg) |
|
2.3. Conducting a test
2.3.1. Ashing of plant material and dissolution of ash
In the crucible weigh with an error of not more than 0.002 g a portion of the test sample prepared according to clause 2.2.1, weighing 0.2 g. The crucible is placed in a cold muffle furnace and the temperature is raised to 250-300 °C. After the cessation of smoke emission, the furnace temperature is raised to (525 ± 25) ° C and calcination is carried out for three hours. Then the crucible is cooled, the ash is moistened with a few drops of distilled water, and 2 cm3 of hydrochloric acid, diluted 1:1, is added from a burette or a dispenser. The crucible is placed in a boiling water bath and the acid is evaporated to wet salts. 5 cm3 of hydrochloric acid, diluted 1:10, is poured into the crucible from a burette or a dispenser, covered with a watch glass and incubated in a boiling water bath for 30 minutes. The ash solution, without filtering, is transferred with a stick through a funnel into a test tube installed in a tripod. Thoroughly wash the crucible, stick and funnel with distilled water, bring the solution to the mark with distilled water, mix and allow the precipitate to settle. The sample for analysis is taken without disturbing the sediment.
It is allowed to separate the ash solution from the undissolved residue by filtration through a paper filter.
At the same time, a control experiment is set up in three repetitions, passing it through all stages of the analysis, excluding taking a sample of the test sample.
It is allowed to increase the sample weight up to (2 ± 0.02) g if it is necessary to analyze the test sample for the content of copper, manganese, and iron. In this case, before determining zinc, the ash solution is diluted ten times with hydrochloric acid diluted 1:40.
2.3.2. Determination of zinc in ash solution
2.3.2.1. The determination of zinc in an ash solution is carried out along the analytical line of 213.9 nm, using an acetylene-air or propane-butane-air flame for atomization. The flame is oxidizing (transparent, blue). The width of the monochromator slit, the gas flow rate, and the current supplying the hollow cathode lamp are set in accordance with the instructions supplied with the instrument and the lamp. When installing the burner relative to the translucent beam, maximum absorption values are achieved for reference solutions.
2.3.2.2. Instruments that allow reading in units of transmission or optical density are calibrated according to a series of reference solutions. When the device has stabilized, the first reference solution that does not contain zinc is introduced into the flame, and the reference point is set (zero value of optical density or 100% transmission). Then the remaining reference solutions are introduced into the flame in order of increasing zinc concentration in them and the readings of the measuring device corresponding to them are recorded.
2.3.2.3. Devices that have digital converters of the measured signal into a concentration value are calibrated using two reference solutions - the first and fourth. Having set the reference point (zero concentration value) according to the first reference solution, the fourth reference solution is introduced into the flame and the position is reached when the reference value is equal to the value of the mass fraction of zinc in plant material corresponding to this solution - 100 million. Alternately introducing the first and fourth reference solutions into the flame , achieve the exact setting of the specified values.
2.3.2.4. Having calibrated the device according to the reference solutions, ash solutions are introduced into the flame and the readings of the measuring device corresponding to them are recorded. Simultaneously conduct a control experiment. Every ten measurements, the first and fourth reference solutions are introduced into the flame to check the calibration characteristics of the device. If during the check deviations of the instrument readings are found, causing a measurement error of more than 3% relative, the calibration of the instrument is corrected or repeated and the last ten ash solutions are analyzed again.
If the reading of the instrument for the ash solution exceeds the reading for the fifth reference solution when operating in the optical density or transmission mode, or for the fourth reference solution when operating in the "concentration" mode, dilute the ash solution with hydrochloric acid diluted 1:40 and repeat the measurement. At the same dilution, the control experiment is repeated.
2.4. Results processing
2.4.1. When using devices that allow you to read readings in units of transmission or optical density, according to the data obtained for reference solutions, a calibration graph is built. On the abscissa axis, mass concentrations of zinc in reference solutions are plotted in terms of mass fractions in plant material in millions indicated in Table 1, and along the ordinate axis - the corresponding readings of the measuring device. According to the calibration graph, the mass concentrations of zinc in the analyzed solutions are found in terms of mass fractions in the plant material in million tons.
2.4.2. When using devices that allow readings in units of concentration, due to the linear dependence of readings on the mass concentration of zinc in the solution in the concentration range used, the reading obtained is equal to the mass concentration of zinc in the analyzed solution in terms of the mass fraction in plant material in ppm.
2.4.3. The mass fraction of zinc in air-dry plant material (), million, is calculated by the formula
where is the coefficient taking into account the dilution of the analyzed solution; when analyzing undiluted solutions \u003d 1, diluted 2 times - 2, etc.;
- mass concentration of zinc in the ash solution in terms of mass fraction in plant material, million;
- arithmetic mean of the values of the mass concentration of zinc obtained in the control experiment, in terms of the mass fraction in the plant material, mln.
The value of the result of the control experiment should not exceed 1/3 of the mass fraction of zinc in the plant material.
The arithmetic mean of the results of two parallel determinations is taken as the final test result. The result is calculated to the first decimal place and rounded up to a whole number.
It is allowed to carry out analysis without parallel determinations if there are standard samples (RS) in the batch of tested samples. The result of a single determination is taken as the test result, if the difference between the content of the element being determined does not exceed 0.7. In this case, selective statistical control of the convergence of parallel definitions is mandatory.
Control analyzes are carried out in two parallel determinations
2.4.4. Permissible discrepancies between the results of parallel determinations () and between the results obtained under different conditions () with a confidence probability = 0.95 should not exceed the following values:
3. PHOTOMETRIC METHOD FOR THE DETERMINATION OF ZINC WITH DITIZONE
The method is based on a comparison of the optical density of a complex compound of zinc with dithizone extracted with carbon tetrachloride from an ash solution and reference solutions with a known zinc concentration.
3.1. Equipment, materials and reagents
3.1.1. To prepare samples for testing and their mineralization - according to clause 2.1.1.
3.1.2. To determine zinc in ash solution, use:
photoelectric colorimeter or spectrophotometer that allows you to work in the wavelength range of 520-540 nm;
laboratory scales of the 2nd accuracy class with the highest weighing limit of 200 g and the 4th accuracy class with the highest weighing limit of 500 g according to GOST 24104;
separating funnels with a capacity of 50-100, 250 and 1000 cm3 according to GOST 25336;
volumetric flasks with ground stoppers of the 2nd accuracy class with a capacity of 50, 100, 500 and 1000 cm 3 according to GOST 1770;
a pipette of the 2nd class of accuracy with a capacity of 5 cm or a dispenser of the same capacity with a dosing error of not more than 1%, made of a material that does not pollute the solution with zinc;
burettes with a tap of the 2nd class of accuracy with a capacity of 100 cm3 or a dispenser with a capacity of 10 cm3 with a dosing error of not more than 1%, made of a material that does not pollute the solution with zinc;
a burette with a tap of the 2nd accuracy class with a capacity of 10 cm3 and a pipette of the 2nd accuracy class with a capacity of 5.10 cm3;
measuring cylinders with a capacity of 10, 25, 100, 250, 500 and 1000 cm3 according to GOST 1770;
laboratory funnels with a diameter of 150 mm according to GOST 25336;
ashless filters, "blue" and "white tape" with a diameter of 15 cm or laboratory filter paper of the FTS brand in accordance with GOST 12026; cleaned from zinc contamination as follows: filters placed in funnels are filled twice with hydrochloric acid diluted 1:100, washed with small portions of distilled water until neutral according to universal indicator paper and dried in air or in an oven at a temperature of not more than 95 ° C ;
universal indicator paper for determining pH 1-10;
sodium acetate 3-aqueous according to GOST 199, analytical grade;
sodium sulphate (sodium thiosulfate) according to GOST 27068, analytical grade;
sulfuric acid according to GOST 4204, chemically pure, diluted with distilled water 1:5 by volume;
aqueous ammonia according to GOST 3760, chemically pure or analytical grade, diluted with distilled water 1:200 by volume;
carbon tetrachloride according to GOST 20288, chemically pure or analytical grade; The suitability of the reagent for analysis is checked as follows: approximately 0.001 g of dithizone is dissolved in 100 ml of carbon tetrachloride and left in a closed bottle for a day in the dark at a temperature of 5-10 °C. If the color of the dithizone solution remains emerald green, carbon tetrachloride is suitable for analysis. A pale green or yellow color of the solution indicates the presence of impurities in carbon tetrachloride that decompose dithizone. In this case, carbon tetrachloride must be purified as follows: 500 cm 3 of carbon tetrachloride are placed in a bottle with a ground stopper with a capacity of 1 dm3, 10 g of activated carbon are added, shaken for 5 minutes and filtered through a paper filter. The treatment is repeated with a new portion of activated carbon. Then carbon tetrachloride is distilled in a glass distillation apparatus assembled on thin sections;
dithizone (diphenylthiocarbazone) according to NTD, analytical grade;
zinc granulated according to NTD, chemically pure;
distilled or deionized water, tested according to clause 2.1.1;
hydrochloric acid according to GOST 3118, chemically pure, diluted with distilled water 1:1, 1:40 and 1:100 by volume;
glacial acetic acid according to GOST 61, chemically pure;
activated carbon according to GOST 4453.
Note. It is allowed to use equipment, measuring utensils and other measuring instruments that have the same or better metrological characteristics.
3.2. Preparing for the test
3.2.1. Preparation of samples for testing - according to clause 2.2.1.
3.2.2. Preparation and purification of dithizone stock solution
Place 0.100 g of dithizone in a separating funnel with a capacity of 250 ml, add 150 ml of carbon tetrachloride and shake vigorously for 10 minutes. The solution is filtered through a paper filter with a blue ribbon into a separating funnel with a capacity of 1000 ml, 250 ml of ammonia diluted 1:200 is added and shaken vigorously for 1 min. After phase separation, the lower organic layer containing dithizone decomposition products is drained and discarded, and the upper aqueous layer containing dithizone is washed 2 times with 3-5 cm of carbon tetrachloride. Then add 10 ml of sulfuric acid diluted 1:5, 500 ml of carbon tetrachloride and shake vigorously for 1 minute. After phase separation, the bottom layer of carbon tetrachloride with dithizone dissolved in it is transferred to another separating funnel or flask, and the aqueous phase is discarded. A solution of dithizone in carbon tetrachloride is washed in a separating funnel 2 times with distilled water in portions of 250 cm 3 and filtered through a dry paper filter, cleaned of zinc contamination, into a dark glass bottle with a ground stopper. The solution is stored at a temperature of 5-10 ° C, no more than 1 me
3.2.3. Preparation of a working solution of dithizone
Place 25 ml of dithizone stock solution in a dry 500 ml volumetric flask, make up to the mark with carbon tetrachloride and mix. The solution is prepared before use.
3.2.4. Preparation of a solution with a mass fraction of sodium thiosulfate 50%
500.0 g of sodium thiosulfate are dissolved in 500 ml of distilled water.
3.2.5. Preparation of Acetate Buffer Solution pH 5
272.0 g of sodium acetate are dissolved in about 500 ml of distilled water, 58 ml of glacial acetic acid are added and the volume of the resulting solution is adjusted to 1 dm with distilled water.
3.2.6. Preparing the masking solution
1 dm of an acetate buffer solution with pH 5 is mixed with 25 ml of sodium thiosulfate solution. The resulting solution is purified from zinc impurities by extraction with a solution of dithizone in carbon tetrachloride. To do this, it is placed in a separating funnel with a capacity of 1000 ml, 5-7 ml of a dithizone solution prepared according to clause 3.2.2 is added (it is allowed to use a dithizone solution not purified from its decomposition products), shaken vigorously for 3 minutes and after phase separation discard the bottom layer. The operation is repeated until the dithizone stops changing its original color. Then the solution to be purified is washed from dithizone by shaking it vigorously with 5–7 cm3 of carbon tetrachloride for 3 min and discarding the organic phase. The washing is repeated until the carbon tetrachloride is no longer stained. The solution is filtered through a paper filter with a white tape, cleaned of zinc contamination, and stored at a temperature of 5-10 °C for no more than 2 weeks.
3.2.7. Preparation of a zinc solution with a mass concentration of 1 mg/cm (solution A) - according to clause 2.2.2.
3.2.8. Preparation of a zinc solution with a mass concentration of 100 µg/cm (solution B)
In a volumetric flask with a capacity of 100 ml, 10 ml of solution A is placed with a pipette, brought to the mark with hydrochloric acid diluted 1:40, and mixed. The solution is stored for no more than 3 months.
3.2.9. Preparation of a zinc solution with a mass concentration of 5 µg/cm (solution D)
In a volumetric flask with a capacity of 100 ml, 5 ml of solution B is placed with a pipette, brought to the mark with hydrochloric acid diluted 1:40, and mixed. The solution is prepared on the day of the test.
3.2.10. Preparation of reference solution
In volumetric flasks with a capacity of 50 cm3, from a burette with a capacity of 10 cm3, the volumes of solution D indicated in Table 2 are poured, adjusted to the mark with hydrochloric acid diluted 1:40, and mixed thoroughly. Solutions are prepared on the day of the test.
table 2
Reference solution number | Solution volume G, cm | Mass concentration of zinc in reference solution, mcg/cm | Mass concentration of zinc in the reference solution in terms of mass fraction in plant material, million (mg/kg) |
3.3. Conducting a test
3.3.1. Ashing of plant material and dissolution of ash - according to clause 2.3.1.
3.3.2. Determination of zinc in ash solution
Samples of 5 cm3 are taken from ash solutions and reference solutions with a dispenser or pipette, placed in separating funnels with a capacity of 50-100 cm3, 10 cm3 of the masking solution are added with a dispenser or from a burette, mixed, and 10 cm3 of dithizone working solution are added with a dispenser or from a burette. Shake the funnels for 1 min. After phase separation, the lower layer of carbon tetrachloride is poured into a cuvette of a photoelectric colorimeter with a translucent layer thickness of 10 mm.
It is allowed to carry out extraction in other hermetically sealed technological containers with a capacity of 50-100 cm3. In this case, phase separation is carried out in separating funnels or one of the phases is taken with a syringe or a pipette with a pear.
The extracts are photometrically compared to the first zinc-free reference solution at a wavelength of 538 nm, or using a light filter with a maximum light transmission in the region of 520-540 nm. Simultaneously conduct a control experiment.
If the optical density value of the extract from the ash solution exceeds the optical density value of the extract from the sixth reference solution, the ash solution is diluted with hydrochloric acid diluted 1:40 and the above operations are repeated in the same order. At the same dilution, the control experiment is repeated.
A proportional change in the volumes of samples of ash solutions, reference solutions and reagent solutions is allowed with a dosing error of not more than 1%.
All work with carbon tetrachloride should be carried out in a fume hood.
3.4. Results processing
3.4.1. According to the results of photometry of extracts from reference solutions, a calibration graph is built, plotting the mass concentrations of zinc in reference solutions on the abscissa axis in terms of mass fractions in plant material in millions indicated in Table 2, and along the ordinate axis - the corresponding optical density values. According to the calibration graph, the mass concentrations of zinc in the analyzed solutions are found in terms of mass fractions in the plant material in million tons.
3.4.2. The mass fraction of zinc in air-dry plant material is calculated according to clause 2.4.3.
3.4.3. Permissible discrepancies between the results of parallel determinations () and between the results obtained under different conditions () with a confidence probability = 0.95 should not exceed the following values:
where is the arithmetic mean of the results of two parallel determinations, million;
- arithmetic mean of the results of two tests performed under different conditions, mln.
The marginal error of the analysis result (), million, with a one-sided confidence probability = 0.95 is calculated by the formula
where is the mass fraction of zinc, ppm (the result of a single determination or the arithmetic mean of the results of two parallel determinations).
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