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GB/T 5451-2001 PDF in English


GB/T 5451-2001 (GB/T5451-2001, GBT 5451-2001, GBT5451-2001)
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GB/T 5451-2001: PDF in English (GBT 5451-2001)

GB/T 5451-2001
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.100;71.040.40
G 23
Replacing GB/T 5451-1985
Testing method for the wettability of dispersible powders of
pesticides
ISSUED ON: JULY 13, 2001
IMPLEMENTED ON: FEBRUARY 01, 2002
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Method summary ... 5
3 Instruments and equipment ... 5
4 Reagents and solutions ... 5
6 Determination steps ... 7
Annex A (standard) Determination method for total hardness of hard water ... 8
Testing method for the wettability of dispersible powders of
pesticides
1 Scope
This Standard is applicable to the determination for the wettability of dispersible
powders of pesticides.
2 Method summary
Pour a certain amount of wettable powder from a specified height into a beaker
containing a certain amount of standard hard water. Determine the time it takes for
complete wetting.
3 Instruments and equipment
Volumetric flasks: 100 mL, 1000 mL.
Pipette: 10 mL.
Polyethylene bottle: 1000 mL.
Thermometer: graduation value is 1°C; range is 0℃ ~50℃ or 0℃ ~100℃.
Beakers: 250 mL (inner diameter is 6.5 cm ± 0.5 cm, height is 9.0 cm ± 0.5 cm), 100
mL, 800 mL, 1000 mL.
Stopwatch.
Graduated cylinders: 20 mL, 100 mL±1 mL, 500 mL.
Watch glass (diameter is 9.0 cm ± 0.5 cm).
Constant temperature water bath.
pH meter.
4 Reagents and solutions
Calcium carbonate: bake at 400℃ for 2 h before use.
Magnesium oxide: bake at 105℃ for 2 h before use.
Anhydrous calcium chloride.
Magnesium chloride with crystal water (MgCl2 • 6H2O).
Ammonia: c(NH3 • H2O)=1 mol/L solution.
Hydrochloric acid: c(HCl)=2 mol/L solution, c(HCl)=1.0 mol/L solution and
c(HCl)=0.1 mol/L solution.
Methyl red: ρ(methyl red)=5 g/L solution.
Sodium hydroxide: c(NaOH)=0.1 mol/L solution.
5 Preparation of standard hard water [ρ(Ca2+ + Mg2+)=342
mg/L]
The following three methods are optional.
5.1 Preparation method one
5.1.1 Preparation of stock solution
5.1.1.1 Solution A -- Preparation of c(Ca2+) = 0.04 mol/L solution
Accurately weigh 4.000 g of calcium carbonate and place it in an 800 mL beaker. Add
a little water to moisten. Then slowly add 82 mL of 1.0 mol/L hydrochloric acid. Stir
thoroughly to combine. After all the calcium carbonate is dissolved, add 400 mL of
water. Boil to remove carbon dioxide. After cooling to room temperature, add 2 drops
of methyl red indicator solution. Neutralize with 1 mol/L ammonia until orange.
Transfer this solution to a 1000 mL volumetric flask. Bring to the volume with water.
Shake well. Store in polyethylene bottles until later use.
5.1.1.2 Solution B -- Preparation of c(Mg2+) = 0.04 mol/L solution
Accurately weigh 1.613 g of magnesium oxide and place it in an 800 mL beaker. Add
a little water to moisten. Then slowly add 82 mL of 1.0 mol/L hydrochloric acid. Stir
well to combine and heat gently. After all the magnesium oxide is dissolved, add 400
mL of water. Boil to remove carbon dioxide. After cooling to room temperature, add 2
drops of methyl red indicator solution. Neutralize with 1 mol/L ammonia until orange.
Transfer this solution to a 1000 mL volumetric flask. Bring to the volume with water.
Shake well. Store in polyethylene bottles until later use.
5.1.2 Preparation of standard hard water
Pipette 68.5 mL of solution A and 17.0 mL of solution B into a 1000 mL beaker. Add
Annex A
(standard)
Determination method for total hardness of hard water
A1 Reagents and solutions
Ammonium chloride.
Concentrated ammonia.
Buffer solution (pH=10): Weigh 67.5 g of ammonium chloride and 570 mL of
concentrated ammonia water. Dilute to 1 L with distilled water. Mix well.
Acid chrome blue R.
Naphthol green.
Potassium sulfate.
Calcium magnesium mixed indicator: Weigh 1.0 g of acid chromium blue R, 2.0 g of
naphthol green and 100.0 g of potassium sulfate. Place them in an agate mortar. Grind
finely and mix well. Store in brown bottles to prevent water absorption and light.
EDTA disodium.
Pure zinc (or zinc oxide).
Concentrated hydrochloric acid.
Methyl orange.
Preparation of EDTA disodium standard titration solution: Weigh 7.44 g of disodium
EDTA. Dissolve in distilled water and dilute to 1000 mL.
Calibration of EDTA disodium standard titration solution: Weigh approximately 0.016
g of pure zinc (or 0.024 g of zinc oxide), accurate to 0.00002 g. Add concentrated
hydrochloric acid to dissolve. Use methyl orange as indicator. Neutralize with
concentrated ammonia to neutrality. Add 1 mL of buffer solution. Add about 0.1 g of
calcium and magnesium mixed indicator. Titrate with EDTA disodium solution to a
greenish color. Do a blank test under the same conditions.
The concentration c (EDTA disodium) of the EDTA disodium standard titration solution
is calculated according to formula (A1) or formula (A2):
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.