ISO 4764:2024

International
Standard
ISO 4764
First edition
Plastics — Polyols for use in the
2024-09
production of polyurethanes
— Determination of degree of
unsaturation by using iodine method
Plastiques — Polyols pour la production des polyuréthanes —
Détermination du degré de non-saturation par la méthode à l'iode
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Solvents and reagents . . 2
5.1 Solvents .2
5.2 Reagents .2
5.2.1 Wijs reagent .2
5.2.2 0,1 N sodium thiosulfate solution .2
5.2.3 KI solution .3
5.2.4 Starch indicator .3
6 Apparatus . 3
7 Procedure . 3
8 Correction . 4
9 Degree of unsaturation after correction. 4
10 Precision and bias . 5
11 Test report . 5
Annex A (informative) Correction of effect by additives . 6
Annex B (informative) Experimental results using conventional polyols . 7
Annex C (informative) Effect of differences of solvent . 8
Bibliography . 9

iii
Foreword
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iv
Introduction
Conventionally, a titration method using mercuric acetate (see ISO 17710) has been used as a method for
measuring a polyether polyol for polyurethanes. However, in recent years, the treatment of mercury waste
liquid associated with analysis has become a global problem.
This document formulates a measurement method to replace the mercuric acetate method.

v
International Standard ISO 4764:2024(en)
Plastics — Polyols for use in the production of
polyurethanes — Determination of degree of unsaturation
by using iodine method
1 Scope
This document specifies a method for quantifying the total unsaturation using an addition reaction of the
interhalogen compound iodine monochloride (ICl), using glacial acetic acid as a solvent as a method for
measuring the total unsaturation of a polyether polyol for polyurethanes. It is not applicable to unsaturated
compounds that are conjugated with a carbonyl group, a carboxyl group, or a nitrile group.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 385, Laboratory glassware — Burettes
ISO 472, Plastics — Vocabulary
ISO 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 4797, Laboratory glassware — Boiling flasks with conical ground joints
ISO 6353-2, Reagents for chemical analysis — Part 2: Specifications — First series
ISO 6353-3, Reagents for chemical analysis — Part 3: Specifications — Second series
ISO 8655-2, Piston-operated volumetric apparatus — Part 2: Pipettes
ISO 8655-3, Piston-operated volumetric apparatus — Part 3: Burettes
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
After dissolving the sample in a solvent, the carbon-carbon unsaturated compound in the sample is added
with glacial acetic acid solution of iodine monochloride (Wijs reagent) and left in a dark place to add iodine.
After completion of the addition reaction, add aqueous solution of potassium iodide, liberate iodine and
titrate with a sodium thiosulfate solution. When the colour of the solution turns pale yellow, add a starch
solution and titrate until the blue disappears. The degree of unsaturation is calculated from the difference
from the blank measured at the same time.

5 Solvents and reagents
5.1 Solvents
Use analytical-grade solvents, such as
5.1.1 methanol, as specified in ISO 6353-2,
5.1.2 ethanol, as specified in ISO 6353-2,
5.1.3 normal propanol,
5.1.4 2-propanol, as specified in ISO 6353-3,
5.1.5 1-butanol, as specified in ISO 6353-3,
5.1.6 cyclohexane, as specified in ISO 6353-2, and
5.1.7 chloroform, as specified in ISO 6353.
NOTE The above solvents are only examples and are not limited thereto (shown in Annex C).
5.2 Reagents
5.2.1 Wijs reagent
Iodine monochloride solution (Wijs reagent) shall be prepared as follows.
Dissolve 9,0 g of Iodine, to the nearest 1 mg, in 900 ml of warm glacial acetic acid.
Dissolve 8,0 g of iodine trichloride (ICl ), to the nearest 1 mg, in 60 ml of warm glacial acetic acid.
Then, get together them, and dilute it with acetic acid to make 1 l.
This Wijs reagent should be sealed and stored in a cool and dark place.
5.2.2 0,1 N sodium thiosulfate solution
Dissolve 26 g of sodium thiosulfate pentahydrate (Na S O ·5H O) (specified in ISO 6353-2), to the nearest
2 2 3 2
1 mg, in water to make 1 l, and add 0,1 g of sodium carbonate (Na CO ) (specified in ISO 6353-2), to the
2 3
nearest 1 mg.
This solution is standardized with potassium iodate (KIO ) as follows.
Put 40 mg of KIO , to the nearest 1 mg, into a 300 ml flask with a stopcock and dissolve it in 30 ml of water.
Add 2 g of potassium iodide (KI), to the nearest 1 mg, and dissolve.
Add 5 ml of 2 mol/l hydrochloric acid solution.
The free iodine is quickly titrated with a Na S O solution using starch as an indicator.
2 2 3
The normality of the Na S O solution is calculated by Formula (1).
2 2 3
F = W / (35,67 × V) (1)
where
F is the normality of Na S O solution;
2 2 3
W is the mass of the KIO , in mg;
V is the volume of the Na S O solution required for the titration of KIO , in ml.
2 2 3 3
5.2.3 KI solution
Dissolve 2 g of KI in 100 ml of water.
5.2.4 Starch indicator
Make 10 g of soluble starch into a paste, dissolve it in 200 ml of hot water, and stir rapidly and cool.
Add about 10 g of thymol as a stabilizer.
6 Apparatus
Usual laboratory apparatus and, in particular, the following.
6.1 Weighing scoops, suitable for the test portion and for insertion into the flasks.
6.2 Conical flasks, with a capacity of 500 ml and 300 ml, with a stopcock in accordance with ISO 4797.
6.3 Analytical balance, with a readability of 0,000 1 g and weighing accuracy of 0,001 g.
6.4 Volumetric flask, with a capacity of 1 000 ml (1 l), in accordance with ISO 1042, class A.
6.5 Pipette, with a capacity of 2 ml and 25 ml ISO 648, class A, fitted with an aspiration bulb, or automatic
one, specified in ISO 8655-2.
CAUTION — Do not use a mouth pipette for the Wijs reagent.
6.6 Burette, with capacity of 25 ml and 50 ml, graduated in 0,1 ml divisions, ISO 385, class A, or automatic
one specified in ISO 8655-3.
7 Procedure
Procedure, using methanol as a solvent for one thing, shall be carried out as follows.
Weigh 10
...