ISO 17319:2015
(Main)Fertilizers and soil conditioners — Determination of water-soluble potassium content — Potassium tetraphenylborate gravimetric method
Fertilizers and soil conditioners — Determination of water-soluble potassium content — Potassium tetraphenylborate gravimetric method
ISO 17319:2015 specifies a gravimetric method for the determination of the water-soluble potassium content of test solutions of fertilizers. It is suitable for use in arbitration and for reference purposes. ISO 17319:2015 is applicable to those fertilizers containing more than 1,0 % K2O or equivalent amount of K content.
Matières fertilisantes — Dosage de la teneur en potassium — Méthode gravimétrique au tétraphénylborate de potassium
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 17319
First edition
2015-05-15
Fertilizers and soil conditioners —
Determination of water-soluble
potassium content — Potassium
tetraphenylborate gravimetric method
Matières fertilisantes — Dosage de la teneur en potassium —
Méthode gravimétrique au tétraphénylborate de potassium
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 1
5 Apparatus and materials. 2
6 Test solution . 2
7 Procedure. 2
7.1 Aliquot portion of test solution . 2
7.1.1 Procedure in the presence of cyanamide and/or organic materials . 2
7.1.2 Procedure in the absence of cyanamide and/or organic materials . 3
7.2 Determination . 3
7.3 Blank test . 3
7.4 Periodic quality control . 3
8 Expression of results . 3
8.1 Calculation . 3
8.2 Precision . 4
8.2.1 Ring test . 4
8.2.2 Repeatability, r .4
8.2.3 Reproducibility, R .4
9 Test report . 4
Annex A (informative) Report of Method Accuracy . 5
Annex B (informative) Interlaboratory testing .13
Bibliography .19
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 134, Fertilizers and soil conditioners.
iv © ISO 2015 – All rights reserved
INTERNATIONAL STANDARD ISO 17319:2015(E)
Fertilizers and soil conditioners — Determination
of water-soluble potassium content — Potassium
tetraphenylborate gravimetric method
1 Scope
This International Standard specifies a gravimetric method for the determination of the water-soluble
potassium content of test solutions of fertilizers. It is suitable for use in arbitration and for reference
purposes.
This International Standard is applicable to those fertilizers containing more than 1,0 % K O or
equivalent amount of K content.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 5317, Fertilizers — Determination of water-soluble potassium content — Preparation of the test solution
3 Principle
Precipitation of potassium ions present in an aliquot portion of the test solution (previously treated
with bromine water and activated charcoal if cyanamide and/or organic materials are present) by
sodium tetraphenylborate in a weakly alkaline medium in the presence of disodium ethylenediamine-
tetraacetatedihydrate (EDTA disodium salt) to eliminate interference by ammonium ions and other
metal cations.
Filtration of the precipitate, drying and weighing.
4 Reagents
WARNING — Sodium hydroxide is corrosive, bromine is corrosive, oxidative and toxic. The related
operations shall be performed in fume hood. This standard does not point out all possible safety
problems, and the user shall bear the responsibility to take proper safety and health measures,
and ensure the operations compliant with the conditions stipulated by the related laws and
regulations of the state.
During the analysis, use only reagents of recognized analytical grade, and water conforming to grade 3
of ISO 3696:1987
4.1 Sodium tetraphenylborate, approximately 15 g/L solution.
Dissolve 7,5 g of sodium tetraphenylborate [NaB(C H ) ] in 480 ml of water. Add 2 ml of the sodium
6 5 4
hydroxide solution (4.4) and 20 ml of a 100 gram/litre (g/L) solution of magnesium chloride hexahydrate
(MgCl ·6H O). Stir for 15 min and filter through the filter paper (5.2).
2 2
This solution may be stored in a plastics bottle for not longer than 1 month. Filter immediately before
use.
4.2 Sodium tetraphenylborate, wash solution.
Dilute 1 volume of the Sodium tetraphenylborate solution (4.1) with 10 volumes of water.
4.3 EDTA, disodium salt, 40 g/l solution.
Dissolve 4,0 g EDTA disodium salt in water in 100 ml graduated flask. Make up to the volume and mix.
4.4 Sodium hydroxide, 400 g/L solution.
4.5 Phenolphthalein, 5 g/L ethanolic solution.
Dissolve 0,5 g of phenolphthalein in 100 ml of 95 % (volume fraction) ethanol.
4.6 Bromine water, saturated solution, approximately 3,2 % (w/v) bromine; shelf life of less than 6
months.
4.7 Charcoal, activated, which does not adsorb or liberate potassium ions.
5 Apparatus and materials
During the analysis, use only glassware of grade A, and the following:
5.1 Gooch crucibles, having a sintered glass or porcelain disc of porosity grade P 10 or P 16 (pore size
index of 4 μm to 16 μm).
5.2 Quantitative filter paper (intermediate speed).
5.3 Drying oven, capable of being controlled at 120°C ± 5°C.
5.4 Usual laboratory equipment, including pipettes, beakers (250 ml), and volumetric flasks, etc.
6 Test solution
Use the clear solution prepared as specified in ISO 5317, also described as follows:
Weigh, to the nearest 0,001 g, 5 g of the prepared test sample to form the test portion. Transfer the
test portion to the flask with 400 ml of water. Bring to a boil and continue to boil for 30 min. Cool the
contents of the flask and transfer to the volumetric flask. Dilute to the mark, mix well and filter into a
dry beaker. Discard the first 50 ml of filtrate.
7 Procedure
7.1 Aliquot portion of test solution
7.1.1 Procedure in the presence of cyanamide and/or organic materials
Preparation of the test solution as specified in ISO 5317.
Transfer, by means of a pipette, an aliquot portion, V1, of the test solution (Clause 6), containing 50 mg to
100 mg of potassium oxide (K O), preferably about 80 mg, to a 250 ml beaker. Add 5 ml of the bromine
water (4.6) and boil the solution until all the bromine has been removed and then, if necessary, to reduce
the volume to less than 100 ml. Allow the solution to cool to ambient temperature and transfer it to a
2 © ISO 2015 – All rights reserved
100 ml volumetric flask. Add about 0,5 g of the activated charcoal (4.7) and shake vigorously. Dilute with
distilled water to the mark and mix well.
Filter the solution and use a pipette to transfer 50 ml of the filtrate into a 250 ml beaker.
7.1.2 Procedure in the absence of cyanamide and/or organic materials
Transfer, by means of a pipette an aliquot portion, V1, of the test solution (Clause 6) containing 25 to
50 mg (preferably 40 mg) of K O to a 250 ml beaker and adjust the volume to approximately 50 ml by
dilution or evaporation.
NOTE If the content of fertilizer sample cannot be specified, use the procedure described in 7.1.1.
7.2 Determination
Further treat the aliquot portion of the test solution (7.1) as follows.
Add 20 ml of the EDTA solution (4.3) and 3 to 5 drops of the phenolphthalein solution (4.5). Add, drop by
drop, the sodium hydroxide solution (4.4) until a pink colour appears and then add 1 ml of the sodium
hydroxide solution in excess.
Slightly boil for 15 min.
The solution should remain pink. If it does not, add 1 to 3 drops of the phenolphthalein solution (4.6)
and, if necessary, restore the pink colour by adding, drop by drop, the sodium hydroxide solution. (4.5).
Remove the beaker from the steam bath and immediately add, drop by drop, while stirring, 30 mL of the
tetraphenylborate solution (4.1).
Continue stirring for 1 min then cool rapidly to ambient temperature in running water and allow to
stand for 15 min.
Weigh the filter crucible (5.1) previously dried in the oven (5.3) controlled at 120 ± 5 °C, and cooled in a
desiccator and then weighed to the nearest 0,000 1 g.
Decant the supernatant liquid through the crucible. Rinse the beaker and precipitate 3 to 5 times with a
total of about 40 ml of the wash solution (4.2), followed by 5 ml of water.
Dry the crucible and precipitate in the oven (5.3) controlled at 120 ± 5 °C for 90 minutes, allow to cool in
a de
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.