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HJ 631-2011: Soil. Determination of exchangeable acidity by barium chloride extraction-titration method
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Soil. Determination of exchangeable acidity by barium chloride extraction-titration method
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HJ 631-2011
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Basic data | Standard ID | HJ 631-2011 (HJ631-2011) | | Description (Translated English) | Soil. Determination of exchangeable acidity by barium chloride extraction-titration method | | Sector / Industry | Environmental Protection Industry Standard | | Classification of Chinese Standard | Z18 | | Classification of International Standard | 13.080 | | Word Count Estimation | 9,996 | | Date of Issue | 2011-12-06 | | Date of Implementation | 2012-03-01 | | Quoted Standard | HJ 613; HJ/T 166 | | Regulation (derived from) | Department of Environmental Protection announcement No. 85 of 2011 | | Issuing agency(ies) | Ministry of Ecology and Environment | | Summary | This standard specifies the determination of exchangeable acidity in soil barium oxide extraction titration method. This standard applies to acid soil exchangeable acidity. When the sample volume is 2. 50g, extraction volume to 100ml, the standard method detection limit is 0. 50mmol/kg, detection limit is 2. 00mmol/kg. | HJ 631-2011: Soil. Determination of exchangeable acidity by barium chloride extraction-titration method
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Soil.Determination of exchangeable acidity by barium chloride extraction-titration method
National Environmental Protection Standard of the People's Republic
Determination of exchangeable acidity of soil
Barium chloride extraction-titration
Soil -Determination of exchangeable acidity
By barium chloride extraction - titration method
The text shall prevail.
Published on.2011-12-06
2012-03-01 implementation
Ministry of Environmental Protection released
Content
Foreword. II
1 Scope..1
2 Normative references..1
3 Terms and Definitions.1
4 method principle..1
5 Reagents and materials.1
6 instruments and equipment.2
7 samples. 2
8 Analysis steps..3
9 Calculation and representation of results..3
10 precision 4
11 Quality Assurance and Quality Control 4
12 Notes. 4
13 Waste treatment..4
Foreword
In order to implement the Environmental Protection Law of the People's Republic of China, protect the environment, protect human health, and regulate exchangeable soil.
This standard is established for the determination of acidity.
This standard specifies the cesium chloride extraction-titration method for determining the exchangeable acidity in soil.
This standard is the first release.
This standard was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection.
This standard is mainly drafted by. Yangzhou Environmental Monitoring Center Station.
This standard is verified by. Nantong Environmental Monitoring Center Station, Zhenjiang Environmental Monitoring Center Station, Lianyungang Environmental Monitoring
Central Station, Yancheng Environmental Monitoring Center Station and Yizheng City Environmental Monitoring Station.
This standard was approved by the Ministry of Environmental Protection on December 6,.2011.
This standard has been implemented since March 1,.2012.
This standard is explained by the Ministry of Environmental Protection.
Determination of exchangeable acidity of soils - Hydrazine chloride extraction - titration
1 Scope of application
This standard specifies the cesium chloride extraction-titration method for determining the exchangeable acidity in soil.
This standard applies to the determination of exchangeable acidity in acidic soils.
When the sample amount is 2.50g and the constant volume is extracted to 100ml, the detection limit of this method is 0.50mmol/kg.
The lower limit is 2.00 mmol/kg.
2 Normative references
The contents of this standard refer to the terms in the following documents. For undated references, the valid version applies.
In this standard.
HJ 613 Determination of dry matter and moisture in soils - Gravimetric method
HJ/T 166 Technical Specifications for Soil Environmental Monitoring
3 Terms and definitions
Exchangeable acidity exchangeable acidity
The soil is extracted with a neutral salt solution, and the hydrogen ions and aluminum ions adsorbed on the soil colloid are exchanged to make it dissolve.
The solution is then titrated with a sodium hydroxide standard solution and the result is referred to as exchangeable acidity.
4 Principle of the method
Soil samples were extracted with an appropriate amount of barium chloride solution to exchange exchangeable aluminum and exchangeable hydrogen in the soil colloid.
Change, forming trivalent aluminum ions and hydrogen ions into the solution. Take a part of the sample and titrate directly with sodium hydroxide standard solution.
The result obtained is exchangeable acidity. Another part of the sample is taken, and an appropriate amount of sodium fluoride solution is added to form fluoride ions and aluminum ions.
The complex, Al3, is fully complexed and titrated with a sodium hydroxide standard solution, and the result is exchangeable hydrogen.
5 reagents and materials
Analytically pure reagents in accordance with national standards were used for analysis, unless otherwise stated.
Carbon oxide water.
5.1 Carbon dioxide free water
The distilled water was boiled and evaporated in a beaker (evaporation amount of about 10%), and after cooling, it was used, and the electrical conductivity was ≤0.20 mS/m (25 ° C).
Available when used.
5.2 Hydrochloric acid solution (HCl). 15.
5.3 Barium chloride solution. c (BaCl2 · 2H2O) = 0.10 mol/L
Weigh 24.43g of barium chloride (BaCl2·2H2O) dissolved in 1000 ml of water, mix and transfer to a polyethylene bottle for storage.
5.4 sodium hydroxide standard solution. c (NaOH) = 0.1 mol/L
Weigh 110g of sodium hydroxide in 100ml of water, shake it, pour it into a polyethylene container, and seal it to the solution.
bright. 5.4 ml of the supernatant was placed in a 1000 ml volumetric flask, diluted with water to the mark, shaken, and transferred to a polyethylene bottle.
save.
Calibration. Weigh the standard reagent potassium hydrogen phthalate dried to constant weight in a constant temperature drying oven at 105 ° C ~ 110 ° C
0.75g (accurate to 0.0001g), add 50ml of water to dissolve it, add 2 drops of phenolphthalein indicator (5.7), to be calibrated
The sodium hydroxide standard solution was titrated to pink and kept for 30 s without fading. At the same time, use water as a blank test. Sodium hydroxide standard
The concentration of the quasi-solution (mol/L) is calculated according to formula (1).
22.204) (
1000) NaOH (
21 ×−
×=
VV
Mc (1)
In the formula.
c(NaOH)-- concentration of sodium hydroxide standard solution, mol/L;
M-- the mass of potassium hydrogen phthalate, g;
V1-- The volume of sodium hydroxide standard solution consumed when calibrating the potassium hydrogen phthalate standard solution, ml;
V2-- The volume of the sodium hydroxide standard solution consumed when the blank solution is calibrated, ml;
204.22-- molar mass of potassium hydrogen phthalate, g/mol.
Note. The sodium hydroxide standard solution should be calibrated before each batch of samples.
5.5 sodium hydroxide standard solution. c (NaOH) = 0.0020 mol/L
Accurately measure 10.00 ml of sodium hydroxide standard solution (5.4) into a 500 ml volumetric flask and dilute to the mark with water. Storage
Store in a polyethylene bottle.
5.6 sodium fluoride solution. c (NaF) = 1.0 mol/L
Weigh 42.0 g of sodium fluoride dissolved in water, dilute to about 900 ml, and adjust the pH to 7.0 with hydrochloric acid solution (5.2).
Make up to 1000ml with water.
5.7 Phenolphthalein indicator
Weigh 1 g of phenolphthalein in a small amount of ethanol (95%) and dilute to 100 ml with ethanol (95%).
6 Instruments and equipment
6.1 pH meter.
6.2 Constant temperature drying oven. Constant temperature control, can maintain 105 ° C ~ 110 ° C.
6.3 Oscillator. The amplitude is 20mm and the speed can be adjusted.
6.4 Centrifuge. Speed up to 4000 r/min with 50 ml polyethylene centrifuge tube.
6.5 Magnetic stirrer.
6.6 Balance. Accuracy is 0.0001 g.
6.7 Soil sieve. The pore size is 2.0 mm.
6.8 Basic burette. 50 ml.
6.9 Common instruments and equipment used in general laboratories.
7 samples
7.1 Sample collection and preservation
Soil samples were collected and stored in accordance with the relevant regulations of HJ/T 166.
7.2 Preparation of samples
Air dried samples were prepared in accordance with the relevant regulations of HJ/T 166. Air dry the sample through a 2 mm pore size sieve and stir well
Mix well, take two parts by quadruple method, one spare, and another one to stock the stock.
7.3 Determination of moisture
Accurately weigh the appropriate amount of air-dried sample and determine its moisture content according to the provisions of HJ 613.
8 Analysis steps
8.1 Preparation of samples
Add 2.50 g sample (7.2) and 30.00 ml cesium chloride solution (5.3) to a 50 ml polyethylene centrifuge tube and place
The shaker was shaken for 1 h, then centrifuged at 3000 r/min for 10 min on a centrifuge, and the tube was removed. Supernatant
Move into a 100ml volumetric flask. The extraction was repeated twice more, and all the supernatants were combined into the above 100 ml volumetric flask, most
Afterwards, the volume was adjusted to 100 ml with a cesium chloride solution (5.3), to be tested.
Note. When there are a small amount of animal and plant residues in the sample, it can be filtered and measured.
8.2 Preparation of Blank Samples
Without adding a sample, a blank sample was prepared in accordance with the same procedure as in 8.1.
8.3 Determination of exchangeable acidity
Measure 50.00 ml of the sample (8.1) in a 100 ml beaker, add a magnetic stirrer, place on a magnetic stirrer, insert
Enter the pH meter electrode and titrate directly to pH=7.8 with sodium hydroxide standard solution (5.5); or use phenolphthalein as indicator.
Titrate until the color turns pink and ends at 30s without discoloration. Record the consumption of sodium hydroxide standard solution
Dosage (ml). At the same time, take 50.00ml blank sample (8.2) instead of the sample to do the blank test, record the consumption of hydrogen and oxygen
The amount of sodium standard solution (ml).
1V
Empty V
8.4 Determination of exchangeable hydrogen
Measure 50.00 ml of the sample (8.1) in a 100 ml beaker, add a magnetic stirrer, place on a magnetic stirrer, insert
Put into the pH meter electrode, add 2.5ml sodium fluoride solution (5.6), titrate with sodium hydroxide standard solution (5.5) to pH = 7.8;
Or use phenolphthalein as an indicator, titrate until the color just turns pink, and the end point is maintained for 30s without discoloration. Record elimination
The amount of sodium hydroxide standard solution used (ml). At the same time, take 50.00ml blank sample (8.2) instead of the sample to short
In the white test, the amount (ml) of the sodium hydroxide standard solution was recorded.
2V
0V
9 Calculation and representation of results
9.1 Calculation of results
The exchangeable acidity (mmol/kg) of the soil sample was calculated according to formula (2).
1001000) ( 1 w
mV
VcVV
NaOH
××
×××−= empty (2)
In the formula.
AE - exchangeable acidity of soil samples, mmol/kg;
1V -- the volume of the sodium hydroxide standard solution consumed by the direct titration sample, ml;
Empty V -- directly titration blank sample consumption volume of sodium hydroxide standard solution, ml;
NaOHc - concentration of sodium hydroxide standard solution, mol/L;
V -- the volumetric volume of the extract, ml;
sV -- direct titration to measure the volume of the sample, ml;
M-- sample size, g;
W-- Moisture content of the sample, %.
The exchangeable hydrogen (mmol/kg) of the soil sample was calculated according to formula (3).
1001000) ( 02 w
mV
VcVVE
NaOH
××
×××−= (3)
In the formula.
HE -- exchangeable hydrogen in soil samples, mmol/kg;
2V -- volume of sodium hydroxide standard solution consumed when titrating the sample after adding sodium fluoride, ml;
0V -- The volume of the sodium hydroxide standard solution consumed by titration of the blank sample after adding sodium fluoride, ml.
The meaning of other parameters is shown in equation (2).
9.2 Results representation
The valid number of the measurement result is up to 3 digits, and the maximum number of digits after the decimal point is 2 digits.
10 precision
Uniform exchange of acidity of 6.90 mmol/kg, 11.5 mmol/kg and 27.5 mmol/kg in 5 laboratories
The samples were measured and the relative standard deviations in the laboratory were. 3.0% to 8.0%, 5.3% to 7.0%, and 3.4% to 4.2.
%; the relative standard deviations between laboratories were. 3.5%, 3.6%, 3.0%; the repeatability limits were. 1.29mmol/kg, respectively.
2.02 mmol/kg, 2.81 mmol/kg; reproducibility limits were 1.36 mmol/kg, 2.17 mmol/kg, 3.43 mmol/kg, respectively.
11 Quality Assurance and Quality Control
11.1 Make at least 2 blank tests for each batch of samples.
11.2 Make at least 10% parallel samples for each batch of samples. When the measured value is ≤10.0mmol/kg, the maximum allowable relative deviation is ±20%;
The measured value is from 10.0 mmol/kg to 100 mmol/kg, and the maximum allowable relative deviation is ±10%; the measured value is ≥100 mmol/kg,
The maximum allowable relative deviation is ±5%.
11.3 The pH meter is calibrated using a pH standard buffer solution prior to use.
12 Precautions
12.1 If the measurement result is less than 2.00 mmol/kg or more than 400 mmol/kg, the amount of the sample may be appropriately increased or decreased.
12.2 Barium chloride is a highly toxic substance, the operator should do personal protection to avoid contact with the skin and mouth of the barium chloride solution.
Cavity.
12.3 If phenolphthalein is selected as the endpoint of the titration of the indicator, it should be indicated in the test report.
13 Waste treatment
The waste liquid generated during the experiment can be added to the sodium sulfate reaction, disposed of by safe landfill, or placed in a closed container.
Save it and entrust the relevant unit to process it.
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