GB/T 17767.3-2010 English PDF (GBT17767.3-2010)

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GB/T 17767.3-2010: Determination of organic-inorganic compound fertilizers -- Part 3: Total potassium content
GB/T 17767.3-2010
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.080
G 20
Replacing GB/T 17767.3-1999
Determination of organic-inorganic compound fertilizers -
Part 3: Total potassium content
ISSUED ON: JUNE 30, 2010
IMPLEMENTED ON: JANUARY 01, 2011
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
National Standardization Administration.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Reagents and materials ... 4
4 Instruments and equipment ... 5
5 Preparation of specimen solution ... 5
6 Analytical procedures ... 6
Determination of organic-inorganic compound fertilizers -
Part 3: Total potassium content
1 Scope
This Part of GB/T 17767 specifies the determination method of total potassium content
in organic-inorganic compound fertilizers.
This Part is applicable to organic-inorganic compound fertilizers composed of organic
fertilizers and chemical fertilizers; it is also applicable to the determination of total
potassium content of various solid organic fertilizers.
2 Normative references
The provisions in following documents become the provisions of this Part through
reference in this Part of GB/T 17767. For the dated references, the subsequent
amendments (excluding corrections) or revisions do not apply to this Part; however,
parties who reach an agreement based on this Part are encouraged to study if the latest
versions of these documents are applicable. For undated references, the latest edition of
the referenced document applies.
GB/T 8571 Preparation of laboratory samples for compound fertilizers
HG/T 2843 Chemical fertilizer products - Standard volumetric, standard, reagent
and indicator solutions for chemical analysis
3 Reagents and materials
Warning - Hydrogen peroxide, nitric acid, perchloric acid in the reagents are
corrosive and oxidizing; sulfuric acid and sodium hydroxide solutions are
corrosive. Related operations shall be carried out in a fume hood. This standard
does not point out all possible safety issues. Users are responsible for taking
appropriate safety and health measures and ensuring that the conditions specified
in relevant national laws and regulations are met.
The reagents, solutions and water used in this part shall comply with the provisions of
HG/T 2843, when the specifications and preparation methods are not specified.
3.1 Sulfuric acid;
3.2 Hydrogen peroxide;
3.3 Nitric acid;
3.4 Perchloric acid;
3.5 Sodium tetraphenylborate solution precipitant: 15 g/L;
3.6 Sodium tetraphenylborate washing solution: 1.5 g/L;
3.7 Disodium ethylenediaminetetraacetic acid (EDTA) solution: 40 g/L;
3.8 Sodium hydroxide solution: 400 g/L;
3.9 Phenolphthalein: 5 g/L ethanol solution; dissolve 0.5 g of phenolphthalein in 100
mL of 95% (volume fraction) ethanol;
3.10 Potassium oxide standard stock solution: 1.00 mg/mL.
Weigh 1.5828 g of potassium chloride which was dried at 110 °C for 2 h. Dissolve it in
water; adjust the volume to 1 L volumetric flask. Mix well. 1 mL of this solution
contains 1.00 mg of potassium oxide (K2O). Store it in a plastic bottle;
3.11 Potassium oxide standard solution: 100 μg/mL
Pipette 25.0 mL of potassium oxide standard stock solution (3.10) into a 250 mL
volumetric flask. Use water to dilute it to the mark. Mix well. 1 mL of this solution
contains 100 μg of potassium oxide (K2O).
4 Instruments and equipment
4.1 Common laboratory instruments;
4.2 Glass crucible filter: No.4, volume 30 mL;
4.3 Electric constant temperature drying oven: temperature can be controlled at (120 ±
5) °C;
4.4 Flame photometer.
5 Preparation of specimen solution
Make parallel determinations of two samples.
Prepare laboratory samples according to GB/T 8571. When preparing the specimen,
grind the sample until it passes through a 1 mm test sieve. If the sample is difficult to
crush, grind it until it passes through a 2 mm test sieve.
For specimens with potassium content (K2O) < 2%, flame photometry is used for
determination; weigh 2 g of specimen. For specimens with potassium content (K2O) ≥
2%, potassium tetraphenylborate gravimetric method is used for determination. When
2% ≤ potassium content (K2O) < 5%, weigh 4 g of specimen. When potassium content
(K2O) ≥ 5%, weigh 2 g of specimen, accurate to 0.0002 g. Prepare the specimen solution
by one of the following methods.
5.1 Nitric acid-perchloric acid digestion method
Place the specimen in a 250 mL tall beaker. Add 20 mL of nitric acid. Shake carefully.
Heat on an electric hot plate in a fume hood, until it is almost dry. Add 10 mL of
perchloric acid after cooling slightly. Cover with a watch glass. Slowly heat until white
smoke of perchloric acid is emitted. Continue heating until the solution is colorless or
light-colored clear liquid (note that it cannot be evaporated dry!). Cool to room
temperature. Transfer the digestion solution into a 250 mL volumetric flask. Use water
to dilute it to the mark. Mix well. Dry filter it. Discard the first 50 mL filtrate.
5.2 Sulfuric acid-hydrogen peroxide digestion method
Place the sample in a 500 mL conical flask. Add 20 mL of concentrated sulfuric acid
and 3 mL ~ 5 mL of hydrogen peroxide. Shake carefully. Let it stand for 12 h ~ 15 h.
Add 3 mL ~ 5 mL of hydrogen peroxide. Insert a pear-shaped funnel. Slowly heat to
boiling in a fume hood with a 1500 W electric stove. Continue heating for 30 min.
Remove it. If the solution is not clear, add 3 mL of hydrogen peroxide in batches after
cooling slightly. Digest in batches, until the solution is colorless or light-colored clear
liquid. Continue heating for 10 min. Cool to room temperature. Transfer the digestion
solution into a 250 mL volumetric flask. Use water to dilute it to the mark. Mix well.
Dry filter it. Discard the first 50 mL filtrate.
6 Analytical procedures
Make parallel determinations of two samples.
6.1 Potassium tetraphenylborate gravimetric method
This method is used when the potassium oxide content in the specimen is greater than
or equal to 2% (mass fraction).
6.1.1 Principle of the method
In a weakly alkaline medium, potassium ions in the specimen solution are precipitated
with sodium tetraphenylborate. In order to prevent cation interference, an appropriate
amount of disodium ethylenediaminetetraacetic acid (EDTA) can be added in advance,
to make the cations complex with disodium ethylenediaminetetraacetic acid. Filter, dry,
weigh the precipitate.