ISO 17403:2014

Rubber — Determination of magnesium content of field and concentrated natural rubber latices by titration (cyanide-free method)

ISO 17403:2014 specifies a cyanide-free titration method for the determination of the magnesium content in field and concentrated natural rubber latex.

Caoutchouc — Détermination par titrage de la teneur en magnésium du latex de plantation et du latex concentré de caoutchouc naturel (méthode sans cyanure)

General Information

• Status: Published
• Publication Date: 13-Feb-2014
• ICS: 83.040.10 - Latex and raw rubber
• Technical Committee: ISO/TC 45/SC 3 - Raw materials (including latex) for use in the rubber industry
• Drafting Committee: ISO/TC 45/SC 3/WG 2 - Latex
• Current Stage: 9093 - International Standard confirmed
• Start Date: 14-Jun-2024
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO 19918:2017 - Protective clothing — Protection against chemicals — Measurement of cumulative permeation of chemicals with low vapour pressure through materials
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17403
First edition
2014-03-01
Rubber — Determination of
magnesium content of field and
concentrated natural rubber latices by
titration (cyanide-free method)
Caoutchouc — Détermination par titrage de la teneur en magnésium
du latex de plantation et du latex concentré de caoutchouc naturel
(méthode sans cyanure)
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Apparatus . 1
5 Reagents . 2
6 Method A — Determination of magnesium content of field latex .2
6.1 Principle . 2
6.2 Procedure . 3
6.3 Number of determinations . 3
6.4 Calculation of results . 3
6.5 Expression of result . 3
7 Method B — Determination of magnesium content of concentrated latex.4
7.1 Principle . 4
7.2 Procedure . 4
7.3 Number of determinations . 4
7.4 Calculation of results . 5
7.5 Expression of result . 5
8 Test report . 5
Annex A (informative) Precision . 7
Bibliography .10
Foreword
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The committee responsible for this document is ISO/TC 45, Rubber and rubber products, Subcommittee
SC 3, Raw material (including latex) for use in the rubber industry.
iv © ISO 2014 – All rights reserved

INTERNATIONAL STANDARD ISO 17403:2014(E)
Rubber — Determination of magnesium content of field
and concentrated natural rubber latices by titration
(cyanide-free method)
1 Scope
This International Standard specifies a cyanide-free titration method for the determination of the
magnesium content in field and concentrated natural rubber latex.
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 124, Latex, rubber — Determination of total solids content
ISO 648, Laboratory glassware — Single-volume pipettes
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
natural rubber latex concentrate
natural rubber latex from Hevea brasiliensis containing ammonia and/or other preservatives, which has
been subjected to some process of concentration
3.2
field natural rubber latex
natural rubber latex with or without a preservative and prior to concentration or any other processing
Note 1 to entry: The preservative is added to maintain the original state of the latex as it came from the tree.
3.3
magnesium content
content of magnesium equivalent to alkaline-earth metals, mainly magnesium and calcium, present
in all soluble forms that may be titrated with ethylenediaminetetraacetic acid in field or concentrated
natural rubber latex
4 Apparatus
4.1 Burette, 50 cm graduated.
4.2 Analytical balance, accurate to 0,1 mg.
3 3 3
4.3 Volumetric pipettes, of capacities 2 cm , 5 cm and 10 cm complying with the requirements of
ISO 648, class A.
5 Reagents
Use reagents of recognized analytical quality. And, wherever water is specified, use distilled water or
water of equivalent purity.
5.1 Magnesium sulfate solution.
Dissolve 1,232 4 g magnesium sulfate heptahydrate (MgSO ·7H O) in water and make up to 1 dm in a
4 2
3 3 3
flask. 1 cm of this solution contains magnesium which is equivalent to 1 cm of 0,005 mol/dm EDTA.
5.2 EDTA solution, 0,005 mol/dm .
Dissolve approximately 1,86 g of sodium salt of ethylenediaminetetraacetic acid (EDTA) in water and
make up to 1 dm . Standardize against the standard solution of magnesium sulfate specified in 5.1.
5.3 Masking agent solution.
Dissolve sufficient sodium hydrogen sulphide hydrate (NaHS·xH O) to give at least 1,68 g sodium
hydrogen sulfide (NaHS). Transfer into a 100 cm volumetric flask and make up to volume with water.
3 3 3
1 cm of this solution is equivalent to 1 cm of 0,3 mol/dm NaHS.
NOTE If the number of hydrate groups is not indicated (xH O), NaHS content may be calculated from the
percentage of NaHS assay in the specification data. For example, if the percentage of NaHS assay equals 60,0 %,
2,80 g of NaHS·xH O is necessary to give 1,68 g of NaHS.
5.4 Eriochrome black T indicator.
Grind together, in a small pestle and mortar, 0,3 g of Eriochrome black T and 100 g of sodium or potassium
chloride to give a homogeneous mixture.
5.5 Buffer solution of ammonium chloride/ammonium hydroxide.
3 3
Dissolve 67,5 g of ammonium chloride (NH Cl) in 250 cm of deionized water, mix with 570 cm of 25 %
ammonium hydroxide (NH OH) and make up to 1 dm with deionized water. The solution should have
a pH of about 10,5.
5.6 Standardization of EDTA.
3 3
Pipette 10 cm of the standard magnesium sulfate solution into a beaker. Add 200 cm of water and
adjust the pH to 10,3 by adding 6 cm of the buffer solution. Add 0,1 g of Eriochrome black T indicator
and titrate with EDTA solution.
5.7 Calcium hydroxide powder.
6 Method A — Determination of magnesium content of field latex
6.1 Principle
This method determines the soluble concentration of divalent alkaline earth ions present in the latex
after the dilution. The results are expressed as magnesium content on the assumption that other divalent
alkaline earth ions, such as calcium, are only present at the micromolar concentration level.
The latex is diluted with water. The soluble magnesium content in the latex is determined by titration
with the sodium salt of EDTA in the presence of NH Cl/NH OH buffer using sulfide releasing agent as
4 4
masking agent and Eriochrome Black T as indicator.
The magnesium content is expressed as a percentage of the total solids content of latex.
2 © ISO 2014 – All rights reserved

6.2 Procedure
Weigh approximately 2,0 g of the field latex into a conical flask and dilute to 100 cm with water.
Add 2,0 cm of ammonium chloride/ammonium hydroxide buffer solution to keep the pH of latex solution
between 10,0 and 10,5.
3 3
Then add 1,0 cm of 0,3 mol/dm NaHS to the latex solution, mix well and leave the solution for at least
10 s.
Add 0,1 g of Eriochrome black T indicator to the latex solution and mix well.
Then titrate with the standard 0,005 mol/dm EDTA solution until the colour of the solution loses the
last trace of red and becomes pure blue.
At the end of titration, add approximat
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