(Changed edition, Amendment No. 1, 2, 3).
2a. SAFETY REQUIREMENTS
2. ACCEPTANCE RULES
D-mannitol (mannitol) according to TU 6-09-5484;
sodium hydroxide (sodium hydroxide) according to GOST 4328, concentration solutions With(NaOH) = 1 mol/dm 3, 0.5 mol/dm 3, 0.2 mol/dm 3 and 0.1 mol/dm 3, prepared according to GOST 25794.1;
inverted sugar, solution, prepared according to GOST 4517;
ethyl alcohol (ethanol) rectified technical according to GOST 18300 of the highest grade;
phenolphthalein (indicator), solution with a mass fraction of 1% in ethanol, prepared according to GOST 4919.1;
flask Kn-2-250-24/29 TS according to GOST 25336;
ethanol (high grade rectified technical ethyl alcohol according to GOST 18300);
platinum cups 115-2, 117-2, 118-2 according to GOST 6365.
(Changed edition, Amendment No. 3).
filter crucible TF POR10 or TF POR16 according to GOST 25336;
The drug is considered to comply with the requirements of this standard if the mass of phosphates does not exceed 0.009 mg.
It is allowed to complete the determination visually.
If there is disagreement in the assessment of the mass fraction of phosphates, the determination is completed photometrically.
It is allowed to determine the color of molybdenum blue according to GOST 10671.6, section. 1.
The drug is considered to comply with the requirements of this standard if the mass of iron does not exceed 0.002 mg.
It is allowed to complete the definition visually.
(Changed edition, Amendment No. 3).
(Changed edition, Amendment No. 1, 2).
sodium hydroxide solution, which does not contain carbonates, is prepared according to GOST 4517; a solution with a mass fraction of 30% is prepared by appropriate dilution;
the solution is stored in a plastic container;
a solution containing Mg is prepared according to GOST 4212;
titanium yellow, solution with a mass fraction of 0.05%, freshly prepared;
flask Kn-2-100-22 THS according to GOST 25336;
The drug is considered to comply with the requirements of this standard if the color of bromine-mercury paper from the analyzed solution is not more intense than the color of bromine-mercury paper from a solution prepared simultaneously with the test and containing the same volume: 0.0005 mg As , 20 cm 3 of sulfuric acid solution, 0.5 cm 3 of tin dichloride solution and 5 g of zinc.
It is allowed to carry out determination in hydrochloric acid medium.
In case of disagreement in the assessment of the mass fraction of arsenic, the analysis is carried out in a sulfuric acid environment.
3.13 . Determination of the mass fraction of heavy metals
The determination is carried out according to GOST 17319 using the thioacetamide method. The analysis is completed visually. In this case, 2.00 g of the drug is placed in a platinum cup, 25 cm 3 of ethanol (ethyl rectified technical alcohol GOST 18300, premium grade) is added and the drug is dissolved by gently heating on an electric stove and stirring with a glass rod. The solution is evaporated on an electric stove covered with a layer of asbestos (boiling point of triethyl borate 120 °C). The residue is dissolved in 15 cm 3 of ethanol and evaporated again under the same conditions. 15 cm 3 of ethanol is again added to the residue and evaporated again (if necessary, the treatment with alcohol is repeated until the boric acid completely evaporates). To the residue add 1 cm 3 of acetic acid with a mass fraction of 30% (GOST 61), cover the cup with glass and heat for 5 - 7 minutes in a boiling water bath.
The solution is transferred with 20 cm 3 of water into a conical flask with a capacity of 50 cm 3, a 4 cm 3 solution of sodium hydroxide with a mass fraction of 20% is added with stirring, and then the determination is carried out according to GOST 17319 without adding a solution of sodium hydroxide.
The drug is considered to comply with the requirements of this standard if the color of the test solution observed after 10 minutes is not more intense than the color of the solution prepared simultaneously with the test solution and containing the same volume: 0.006 mg Pb, 1 cm 3 solution of acetic acid with a mass fraction of 30%, 4 cm 3 solution of sodium hydroxide with a mass fraction of 20%, 1 cm 3 solution of potassium sodium tartrate and 1 cm 3 solution of thioacetamide.
If necessary, a correction is introduced into the analysis result for the content of heavy metals in the volume of ethanol consumed for decomposition, determined by a control experiment in the residue after evaporation.
3.12 , 3.13. (Changed edition, Amendment No. 1, 2, 3).
4. PACKAGING, LABELING, TRANSPORTATION AND STORAGE
4.1 . The drug is packaged and labeled in accordance with GOST 3885 , with a danger sign on the transport container according to
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BORIC ACID
Official edition E
PUBLISHING HOUSE OF STANDARDS Moscow
UDC 661.651:006.354 Group L12
STATE STANDARD OF THE USSR UNION
BORIC ACID Specifications
Boric acid. Specifications
Date of introduction 01/01/80
This standard applies to boric acid manufactured for the needs of National economy and export.
Boric acid is used in the chemical industry, medicine, glass production, ceramics and other industries.
Formula H3BO3.
The molecular weight of boric acid (according to international atomic masses 1985) is 61.83.
(Changed edition, Amendment No. 3).
1. TECHNICAL REQUIREMENTS
1.1. Boric acid must be manufactured in accordance with the requirements of this standard according to technological regulations approved in the prescribed manner.
1.2. Depending on the application, boric acid is available in four grades: for optical glass melting, A, B and C. The scope of application of the grades is given in the Appendix.
1.1, 1.2. (Changed edition, Amendment No. 1).
Official publication Reproduction prohibited
© Standards Publishing House, 1978 © Standards Publishing House, 1993 Reprint with changes
4.5. Determination of the mass fraction of sulfates
The phototurbidimetric method is based on the formation of a homogeneous finely dispersed precipitate of BaS04 in an acidified solution in the presence of a starch stabilizer or ethylene glycol and measuring the attenuation of the intensity of the light flux with a suspension of barium sulfate using a photocolorimeter.
4.5.1. Equipment, reagents and solutions
GOST 24104-88
Graduated pipettes with a capacity of 1, 5, 10, 20 and 25 cm3.
Stopwatch.
A standard solution containing 0.01 mg S0 4 in 1 cm 3; prepared according to GOST 4212-76, use freshly prepared solution I.
4.5.2. Analysis conditions
The ambient temperature during analysis is (25±5) °C.
At an air temperature below 20°C, before adding barium chloride solution, it is necessary to heat the solutions in a water bath at a temperature of 30-35°C for 15 minutes.
The temperature of the analyzed solutions when constructing a calibration curve and when analyzing samples should be the same in the range (25±5) °C.
4.5.3. Construction of a calibration graph
To construct a calibration curve, place 2.0 in conical flasks with a capacity of 100 cm 3; 4.0; 6.0; 8.0; 10.0 cm 3 stan-
Dart solution I, which corresponds to 0.02; 0.04; 0.06; 0.08; 0.10 mg SO4, the solution volumes are adjusted to 25 cm 3 with water and mixed.
At the same time, prepare a control solution that does not contain solution I.
Add 1 cm 3 of hydrochloric acid solution, 3 cm 3 of starch or ethylene glycol to each solution and mix thoroughly for 1 minute. Then add 3 cm 3 of barium chloride solution and mix again for 1 minute, and then stir periodically every 10 minutes.
After 40 minutes, measure the optical density of the solutions relative to the control solution at a wavelength of 490 nm in cuvettes with a light-absorbing layer thickness of 50 mm.
Each point of the calibration graph must represent the arithmetic mean of at least three parallel determinations.
Based on the data obtained, a calibration graph is constructed, plotting the S0 4 masses contained in solutions in milligrams on the abscissa axis, and the corresponding optical densities values on the ordinate axis.
4.5.4. Preparation of samples of boric acid grades “for optical glass melting”, A and B
(30.00 ± 1.00) g of boric acid grade A or (5.00 ± 0.50) g of product grade “for optical glass melting” or B is placed in a conical flask with a capacity of 250 cm 3, 100 cm 3 of water is added and applied liquid level mark.
Cover the flask with a funnel and dissolve the sample by heating, but do not boil (if necessary, adjust the volume of the solution to the mark with water). The solution is cooled to room temperature and filtered through a blue ribbon filter, previously washed 3-4 times with hot water, discarding the first portions of the filtrate. The filtrate is placed in a conical flask and closed - solution II for grade A, solution III for grades “for optical glass melting” or B.
4.5.5. Preparation of samples of boric acid grade B
(1.0000±0.1000) g of boric acid is placed in a conical flask with a capacity of 250 cm 3, 100 cm 3 of water is added and heated, avoiding boiling, until the sample is dissolved. The solution is cooled to room temperature, transferred to a 500 cm 3 volumetric flask, adjusted to the mark with water and mixed. The solution is filtered through a blue ribbon filter, previously washed 3-4 times with hot water, discarding the first portions of the filtrate - solution IV.
P. 12 GOST f8704-78
4.5.6. Carrying out analysis
25 cm 3 of solution II, 20 cm 3 of solution III and 10 or 5 cm 3 of solution IV are placed in a conical flask with a capacity of 100 cm 3. The volume of solutions is brought to 25 cm 3 with water, 1 cm 3 of hydrochloric acid solution is added and then proceed as when constructing a calibration graph.
4.5.7. Processing the results
The mass fraction of sulfates (Ai) as a percentage is calculated using the formula
m^lOO-V m-V a . 1000“ ’
where gn\ is the mass of sulfates found from the calibration curve, mg;
V is the volume of solution with the sample being analyzed, cm 3 ;
V a is the volume of an aliquot of the solution taken for analysis,
The result of the analysis is taken as the arithmetic mean of the results of two parallel determinations, the absolute discrepancy between which should not exceed the values specified in the table. 1a, with a confidence probability of P = 0.95.
The absolute total error of the analysis result at R = 0.95 is indicated in table. 1a.
4.6. Determination of the mass fraction of iron The mass fraction of iron in boric acid grade “for optical glass melting” is determined according to clause 4.16.
The mass fraction of iron in boric acid grades A, B and C is determined by the photocolorimetric method, which is based on measuring the light absorption of the Fe (II) complex compound with
1,10-phenanthroline or 2,2/-dipyridyl after preliminary reduction of Fe(III) with hydroxylamine hydrochloride.
4.6.1. Equipment, reagents and solutions
Burette with a capacity of 10 cm 3 with a division value of 0.05 cm 3.
General purpose laboratory scales according to GOST 24104-88
Graduated pipettes with a capacity of 1 and 10 cm3.
Buffer solution pH 5. Prepare as follows: 38 g of sodium acetate is dissolved in 300-500 cm 3 of water, transfer the solution to a volumetric flask with a capacity of 1 dm 3, add 58 cm 3 of acetic acid solution, bring the volume of the solution to the mark with water and mix .
Hydroxylamine hydrochloride according to GOST 5456-79. 2.2/-Dipyridyl.
Reagent for iron. Prepared in two ways. First method: to 50 cm 3 of water add 5.8 cm 3 of acetic acid solution, 10 g of hydroxylamine hydrochloride and 0.1 g of 2,2"-dipyridyl, then add 245 cm 3 of water, 3.8 g of sodium acetate and mix again. Second method: add 100 cm 3 of buffer solution to 200 cm 3 of water. 10 g of hydroxylamine hydrochloride 0.1 g
1.10-phenanthroline and stir. Solutions are stored in orange glass bottles.
1,10-phenanthroline.
4.6.2. Construction of a calibration graph
To construct a calibration curve, reference solutions are prepared. In glasses with a capacity of 100 cm 3 place 0.2; 0.5;
1.0; 1.5; 2.0; 4.0; 5.0; 6.0 cm 3 of solution I, which corresponds to 0.002; 0.005; 0.010; 0.015; 0.020; 0.040; 0.050; 0.060 mg iron. Bring the volume of solutions with water to 20 cm 3 and mix.
At the same time, prepare a control solution; containing 20 cm 3 of water.
To each solution add 0.1 cm 3 of acetic acid solution and 5 cm 3 of iron reagent. The solutions are immersed for 10 minutes in a boiling water bath, then cooled, transferred into volumetric flasks with a capacity of 50 cm 3, the volumes of the solutions are adjusted to the mark with water and mixed.
The optical densities of reference solutions are measured relative to the control solution in cuvettes with a light-absorbing layer thickness of 50 mm at a wavelength of 490 nm.
Based on the data obtained, a calibration graph is constructed, plotting the mass of iron contained in the reference solutions in milligrams on the abscissa axis, and the corresponding optical densities values on the ordinate axis.
Each point of the calibration graph must represent the arithmetic mean of at least three results of parallel determinations.
When replacing reagents or a device, check the calibration curve.
4.6.3. Carrying out analysis
(2.00 ± 0.10) g of the product is placed in a glass with a capacity of 100 cm 3, 15 cm 3 of water, 10 cm 3 of sulfuric acid solution, 5 cm 3 of iron reagent are added, heated for 10 minutes in a boiling water bath, cooled, transferred solution into a 50 cm 3 volumetric flask, dilute with water to the mark and mix.
At the same time, prepare a control solution containing all reagents except the product being analyzed.
The optical density of the analyzed solution is measured in relation to the control solution in the same way as when constructing a calibration graph.
4.6.4. Processing the results
The mass fraction of iron (I in percent) is calculated by the formula
t 1 "100 * 2= t* 1000 '
where m x is the mass of iron found from the calibration curve, mg;
t is the mass of the sample, g.
The arithmetic mean of the results of two parallel determinations is taken as the result of the analysis; the absolute discrepancy between them should not exceed the values indicated in the table. 16, with a confidence level of P = 0.95.
|
The absolute total error of the analysis result at P == 0.95 is indicated in table. 16. Table 16 |
4.3-4.6. (Changed edition, Amendment No. 3).
4.7. Determination of the mass fraction of heavy metals
the amount of ethyl alcohol determined by the control experiment in the residue after evaporation.
The error in determining the mass fraction of heavy metals should not exceed 10% of the norm established for this indicator, with a confidence probability of P = 0.95.
(Changed edition, Amendment No. 1, 3).
4.8. Determination of the mass fraction of residue insoluble in water
The mass fraction of the water-insoluble residue in boric acid grade A is determined by a photocolorimetric method based on measuring the optical density of a boric acid solution relative to distilled water.
The mass fraction of the residue insoluble in water in boric acid grades B, B and “for optical glass melting” is determined by a method based on dissolving a sample of boric acid in water when heated, filtering the resulting solution through filter crucibles, drying the insoluble residue to constant weight at a temperature of 105 °C.
4.8.1. Equipment, reagents and solutions
General purpose laboratory scales according to GOST 24104-88
2nd and 4th accuracy classes with the largest weighing limits of 200 and 500 g, respectively.
Laboratory glass thermometer according to GOST 28498-90 s
at a division price of 0.5 °C.
Filter crucible type TF POR 16 according to GOST 25336-82.
Drying cabinet providing heating temperature
4.8.2. Conducting an analysis of a brand A product
(4.0±0.1) g of boric acid is weighed, placed in a glass and dissolved in 100 cm 3 of water heated to (35±5) °C, then the solution is cooled to room temperature.
The optical density of the solution is measured relative to distilled water in a cuvette with a light-absorbing layer thickness of 50 mm at a wavelength of 400 nm.
The product is considered to comply with the requirements of this standard if the optical density does not exceed 0.02.
4.8.3. Conducting product analysis of grades B, B and “for optical glass melting”
(50.00 ± 1.00) g of boric acid grade B and “for optical glass melting” and (20^00 ± 1.00) g grade B are dissolved, respectively, in 500 and 400 cm 3 of water heated to (85 ± 5) °C. The resulting solution is covered with a glass glass for an hour and kept in a boiling water bath until the sample is dissolved, filtered through a filter crucible, previously dried to a constant weight and weighed to the fourth decimal place. The residue on the filter is washed with 300 cm 3 of hot water. The outside of the crucible is washed with distilled water and wiped with filter paper. The filter with the residue is dried in an oven for 1.5 hours at a temperature of (105±5) °C, cooled and weighed with the same accuracy.
4.8.4. Processing the results
The mass fraction of the residue insoluble in water (A 3) as a percentage is calculated using the formula
where gn\ is the mass of the residue in the crucible, g;
m is the mass of a sample of boric acid, g.
The result of the analysis is taken as the arithmetic mean of the results of two parallel determinations, the absolute discrepancy between which should not exceed the values indicated in the table. 1c, with a confidence level of P = 0.95.
The absolute total error of the analysis result at P = 0.95 is indicated in table. 1st century
Table 1c
4.9. Determination of the mass fraction of calcium The photocolorimetric method is based on measuring the optical
ical density of colored solutions of a complex compound of calcium with calcium. Boric acid is first removed from the solution by evaporation with ethyl alcohol.
4.9.1. Equipment, reagents and solutions
Burette with a capacity of 5 cm 3 with a division value of 0.02 cm 3.
General purpose laboratory scales according to GOST 24104-88
2nd accuracy class with the largest weighing limit of 200 g.
Photoelectric laboratory colorimeter according to specifications
3-3.1766-82, TU 3-3.1860-85, TU 3-3.2164-89.
The dit in the test tubes is brought to 2 cm 3 with water, 1 cm 3 of sodium hydroxide and 2 cm 3 of acetone are added, mixed, then 5 cm 3 of calcium solution is added and mixed again. At the same time, prepare a control solution with the same amounts of reagents, but without solution II. After 2 minutes, but no later than 10 minutes after adding the calcium solution, measure the optical density of the prepared solutions relative to water using a photocolorimeter in cuvettes with a light-absorbing layer thickness of 20 mm, closed with lids, at a wavelength of 590 nm. From the found optical density of the control solution, the optical densities of the reference solutions are subtracted. To construct each point of the calibration graph, calculate the arithmetic mean of the results from at least three parallel determinations of optical densities.
Based on the data obtained, a calibration graph is constructed, plotting the mass of calcium contained in the reference solutions in milligrams on the abscissa axis, and the corresponding differences in the optical densities of the control solution and reference solutions along the ordinate axis. The calibration curve is checked when changing reagents or instruments.
4.9.3. Carrying out analysis
(0.1000±0.0100) g of product of grades “for optical glass melting” and B or (0.2000±0.0100) g of product of grade A is placed in a platinum cup, 5 cm 3 of ethyl alcohol is added, 0.1 cm 3 hydrochloric acid solution and evaporate to dryness in a fume hood in a water bath under conditions that exclude the possibility of calcium contamination. The operation is repeated three times. Then add 2 cm 3 of water, 1 cm 3 of sodium hydroxide solution, 2 cm 3 of acetone to the cup, mix, add 5 cm 3 of calcium and mix again. The contents of the cup are transferred to a test tube and capped.
At the same time, a control experiment is carried out through all stages of the analysis. After 2 minutes, but no later than 10 minutes, measure the optical densities of the resulting solutions relative to water in the same way as when constructing a calibration graph. The optical density of the analyzed solution is subtracted from the found optical density of the control solution. Based on the obtained optical density value, the mass of calcium in the analyzed sample in milligrams is determined using a calibration graph.
4.9.4. Processing the results
The mass fraction of calcium (J 4) as a percentage is calculated using the formula
1.3. According to physical and chemical indicators, boric acid must meet the requirements and standards specified in table. 1.
Table 1
1. Appearance
white powder
2. Mass fraction of boric acid (H 3 B0 3), %, not less
3. Mass fraction of chlorides (C1), %, no more
4. Mass fraction of sulfates (S0 4), %, no more
5. Mass fraction of iron (Fe), %, no more
6. Mass fraction of heavy metals (Pb), %, no more
7. Mass fraction of residue insoluble in water, %, no more
8. Mass fraction of calcium (Ca), %, no more
9. Mass fraction of arsenic (As), %, no more
10. Mass fraction of phosphates (P0 4), %, no more
11. Mass fraction of residue non-volatile when treated with ethyl alcohol, %, no more
12. Residue on a sieve with mesh according to GOST 6613 - -86,%:
04K no more
0063K no less
|
Fine crystalline free-flowing color |
|||||||||||||||||||||||||||||||||||||||
|
Not standardized Not standardized normalized 15 Not standardized 75 " |
||||||||||||||||||||||||||||||||||||||
Not standardized
x Shl ooo >
where m is the mass of calcium found from the calibration curve, mg;
t is the mass of a sample of boric acid, g.
The result of the analysis is taken as the arithmetic mean of the results of two parallel determinations, the absolute discrepancy between which for measurement ranges from 0.001 to 0.002% and from 0.002 to 0.005% should not exceed 0.0007 and 0.0014%, respectively, with a confidence probability of P = 0.95.
The absolute total error of the analysis result for the indicated ranges is ±0.0003 and ±0.001%, respectively, with a confidence level of P = 0.95.
4 8, 4.9. (Changed edition, Amendment No. 3).
4.10. Determination of the mass fraction of arsenic
Boric acid enters the body when inhaled in the form of vapor or aerosol. Dissolved in water, it penetrates well through damaged areas of the skin (eczema, cracks, burns), causing poisoning of the human body.
The maximum permissible concentration of boric acid in the air of the working area is 10 mg/m 1 .
2.2. Determination of the content of boric acid in the air is carried out according to methods approved by the USSR Ministry of Health. The determination is based on the reaction of boric acid with 1,1-diantrimide in concentrated sulfuric acid to form a blue colored compound.
2.3. The air released into the atmosphere must be purified to the established maximum permissible standards.
Wastewater generated as a result of flushing and wet cleaning must be collected in a receiver and sent for neutralization to a neutralization station or returned to the technological process.
2.4. Production and laboratory premises in which work with boric acid is carried out must be equipped with supply and exhaust ventilation in accordance with GOST 12.4.021-75, ensuring the air condition of the working area in accordance with the requirements of GOST 12.1.005-88.
2.5. Those working with boric acid must use personal protective equipment in accordance with GOST 12, 4.034-85 to protect their respiratory organs, safety glasses for their faces and eyes in accordance with GOST 12.4.013-85, as well as special clothing and shoes and hand protection - in accordance with GOST 12.4. 103-83.
2.6. Analyzes of boric acid must be carried out in compliance with the basic rules of safe work in chemical laboratories approved in the prescribed manner.
Sec. 2. (Changed edition, Amendment No. 1). 1
less than 5% of product units, for small batches (less than 60 units) - at least three units.
3.4. The manufacturer is allowed to measure the following indicators periodically, at least once a month:
in a product of grade A - mass fractions of heavy metals (Pb), water-insoluble residue, calcium (Ca), arsenic (As), phosphates (PO4);
in a product of brand B - mass fractions of chlorides (C1), heavy metals (Pb), water-insoluble residue, calcium (Ca), arsenic (As), phosphates (P0 4);
in a product of grade B - mass fractions of sulfates (S0 4), iron (Fe), and water-insoluble residue.
3.5. If unsatisfactory analysis results are obtained for at least one indicator, a repeat analysis is carried out on it on a double sample from the same batch.
The results of the retest apply to the entire lot.
Sec. 3. (Modified edition, Rev. JNIar 3).
4. METHODS OF ANALYSIS
4.1. Sample selection
4.1a. General requirements
The results of the analysis of each indicator are rounded to the smallest digit of the total error.
It is allowed to use other methods of analysis that have passed metrological certification and have accuracy characteristics not lower than the methods provided for by this standard.
In case of disagreement in assessing the quality indicator, the analysis is carried out using the methods specified in this standard.
It is allowed to use other measuring instruments with metrological characteristics and equipment with technical characteristics not worse, as well as reagents of quality not lower than those specified in this standard.
(Introduced additionally, Amendment No. 3).
4.1.1. To check the quality of boric acid to be packaged, spot samples are taken at regular intervals manually or with a mechanical sampler of any design, providing a spot sample weighing at least 100 g from 3-5 tons of product.
Spot samples of the packaged product are taken with a sampler of any design, immersing it at least 1/2 deep.
bins of a bag or container. The mass of a spot sample must be at least 100 g.
The manufacturer is allowed to take spot samples from bags and containers before sewing or tying them. (Changed edition, Amendment No. 2).
4.1.2. Sampling is carried out according to the following scheme:
Spot samples are taken from packaging units of products selected for control or from the mass of the product before packaging;
selected point samples are combined together, mixed and form a combined sample;
From the combined sample, using the quartering method, an average sample weighing at least 500 g is taken for analysis.
4.1.3. An average sample of boric acid is placed in a dry glass or plastic jar or plastic bag. The jar is tightly closed and the bag is tied.
The following data is applied to the jar or bag with the sample: name of the manufacturer; Product name; batch number; date of sampling.
4.1.2. 4.1.3. (Changed edition, Amendment No. 3).
4.2. The appearance of the product is determined visually
4.3. Determination of the mass fraction of boric acid
The technique is based on the alkalimetric titration of complex compounds of boric acid with polyhydric alcohols using the indicator phenolphthalein.
4.3.1, Equipment, reagents and solutions Filter paper.
Burette with a capacity of 50 cm 3 with a division value of 0.1 cm 3.
General purpose laboratory scales in accordance with GOST 24104-88 of the 2nd and 4th accuracy classes with the largest weighing limits of 200 and 5 kg, respectively.
Funnel for filtering under vacuum according to GOST 25336 -
4.3.2. Preparation of twice recrystallized succinic acid
(100.0 ± 1.0) g of succinic acid is dissolved by boiling in 170 cm 3 of water. The hot solution is quickly filtered on a funnel with a cut spout through filter paper and cooled with continuous stirring. The separated crystals are filtered on a Buchner funnel and recrystallized again, dissolving after boiling in 140 cm 3 of water. The resulting succinic acid crystals are dried between sheets of filter paper until they no longer stick to the glass rod.
Before use, succinic acid is dried in an oven at a temperature of (105±5) °C to constant weight.
4.3.3. Setting the correction factor to 0.5 mol/dm 3 sodium hydroxide solution
(1.0000±0.1000) g of succinic acid is placed in a conical flask with a capacity of 250 cm 3 and dissolved, heating to boiling, in 50 cm 3 of distilled water that does not contain carbon dioxide.
The solution is titrated hot with sodium hydroxide in the presence of 3-4 drops of phenolphthalein until a pink color appears that does not disappear within 50-60 s.
The correction factor (K) of 0.5 mol/dm 3 sodium hydroxide solution is calculated using the formula
K= V- 0.02952 '
where m is the mass of a sample of succinic acid, g;
V is the volume of sodium hydroxide solution with a concentration of 0.5 mol/dm 3 used for titration, cm 3 ; 0.02952 - weight of succinic acid, corresponding to 1 cm 3 of hydroxide solution. sodium concentration is exactly 0.5 mol/dm 3, g.
The result of the analysis is taken as the arithmetic mean of the results of three parallel determinations, the permissible differences between which should not exceed 0.001 with a confidence probability of P -0.95.
4.3.4. Preparation of invert sugar solution
(5.00 ± 0.05) kg of refined sugar is dissolved in 3.2 dm 3 of distilled water that does not contain carbon dioxide, heated to a temperature of (80 ± 5) ° C and 408 cm 3 of 0.1 mol is added dm 3 of hydrochloric acid solution, stirred and kept at this temperature for 1 hour. Then the sugar solution is filtered, 460 cm 3 of 0.1 msl/dm 3 of sodium hydroxide solution is added to neutralize, cooled and adjusted with distilled water that does not contain carbon dioxide, to 10 dm 3, mix thoroughly.The resulting solution is neutralized for phenolphthalein with solutions of sodium hydroxide with a concentration of 0.1 mol/dm 3 and hydrochloric acid until the color of phenolphthalein discolors from one drop of hydrochloric acid solution.
4.3.5. Carrying out analysis
(1.0000 ± 0.1000) g of boric acid is placed in a conical flask with a capacity of 250 cm 3, dissolved in 100 cm 3 of water heated to (65 ± 5) ° C, free of carbon dioxide, cooled, 10 g of mannitol or sorbitol are added , or 60 cm 3 of sugar solution, or 10 cm 3 of glycerin solution, 5 drops of phenolphthalein and titrated with a solution of sodium hydroxide with a concentration of 0.5 mol/dm 3 until a pink color appears. After this, add another 2 g of mannitol or sorbitol, or 20 cm 3 of a sugar solution, or 5 cm 3 of a glycerin solution and, if the solution becomes discolored, titrate again until a pink color appears. This operation is carried out until the color of the solution ceases to disappear when mannitol or sorbitol, or a sugar solution, or a glycerin solution is added.
4.3.6. Processing the results
The mass fraction of boric acid (X) as a percentage is calculated
according to the formula
tp 1
where V is the volume of sodium hydroxide solution with a concentration of 0.5 mol/dm 3 used for titration, cm 3 ; 0.03092 - mass of boric acid corresponding to 1 cm 3 of sodium hydroxide solution with a concentration of exactly 0.5 mol/dm 3, g;
K is the correction factor of the titrated sodium hydroxide solution;
m is the mass of the sample, g.
The result of the analysis is taken as the arithmetic mean of the results of two parallel determinations, the absolute discrepancy between which should not exceed 0.3% with a confidence probability of P = 0.95.
The absolute total error of the analysis result is ±0.6% with a confidence level of P = 0.95.
4.4. Determination of the mass fraction of chlorides
The determination is carried out according to GOST 10671.7-74. In this case, (30.00 ± 1.00) g of boric acid is placed in a conical flask with a capacity of 150 cm 3, 120 cm 3 of water is added and a mark is applied at the liquid level. The flask is covered with a funnel and the sample is dissolved by heating in a boiling water bath (if necessary, the volume of the solution is adjusted to the mark with water). The solution is cooled to room temperature and filtered through a dense ashless “blue ribbon” filter, previously washed with a solution of nitric acid according to GOST 4461-77 with a mass fraction of 1%.
40 cm 3 of filtrate (corresponding to 10 g of product) for brand A or 20 ml of filtrate (corresponding to 5 g of product) for brand B is placed in a conical flask with a capacity of 100 cm 3 (with a mark at 50 cm 3), add 20 cm 3 of water for brand B and further determination is carried out by visual nephelometric and phototurbidimetric (method 2) methods. The initial sample for the phototurbidimetric method is (45.00±1.00) g.
The product is considered to comply with the requirements of this standard if the mass of chlorides does not exceed for brands:
A - 0.010 mg;
B - 0.050 mg.
The error in determining the mass fraction of chlorides should not exceed 10% of the norm established for this indicator, with a confidence probability of P = 0.95.
3.1. Boric acid is taken in batches. A batch is considered to be a quantity of a product that is homogeneous in terms of quality, in a volume of no more than 1000 tons and documented in one quality document.
The quality document must contain:
name of the manufacturer and its trademark;
name, brand and grade of product;
batch number;
date of manufacture;
net weight;
results of analyzes performed or confirmation of product quality compliance with the requirements of this standard;
designation of this standard.
The manufacturer is allowed to distribute the result of the analysis of shift production to all batches formed from it.
3.2. To verify the quality of boric acid meets the requirements of this standard, acceptance tests are carried out.
3.3. To control the quality of the product, a random sample is selected from a batch of boric acid, the volume of which is not