prEN ISO 18724

SLOVENSKI STANDARD
01-julij-2024
Kakovost vode - Določanje kroma (IV), raztopljenega v vodi - Fotometrijska
metoda (ISO/DIS 18724:2024)
Water quality - Determination of dissolved chromium(VI) in water - Photometric method
(ISO/DIS 18724:2024)
Wasserbeschaffenheit - Bestimmung des gelösten Chrom(VI) in Wasser -
Photometrisches Verfahren (ISO/DIS 18724:2024)
Qualité de l'eau - Détermination du chrome dissous(VI) dans l'eau - Méthode
photométrique (ISO/DIS 18724:2024)
Ta slovenski standard je istoveten z: prEN ISO 18724
ICS:
13.060.50 Preiskava vode na kemične Examination of water for
snovi chemical substances
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 18724
ISO/TC 147/SC 2
Water quality — Determination of
Secretariat: DIN
dissolved chromium(VI) in water —
Voting begins on:
Photometric method
2024-06-04
Qualité de l'eau — Détermination du chrome dissous(VI) dans
Voting terminates on:
l'eau — Méthode photométrique
2024-08-27
ICS: 13.060.50
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Reference number
ISO/DIS 18724:2024(en)
DRAFT
ISO/DIS 18724:2024(en)
International
Standard
ISO/DIS 18724
ISO/TC 147/SC 2
Water quality — Determination of
Secretariat: DIN
dissolved chromium(VI) in water —
Voting begins on:
Photometric method
Qualité de l'eau — Détermination du chrome dissous(VI) dans
Voting terminates on:
l'eau — Méthode photométrique
ICS: 13.060.50
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2024
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
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Published in Switzerland Reference number
ISO/DIS 18724:2024(en)
ii
ISO/DIS 18724:2024(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Interferences . 2
4.1 General .2
4.2 Sampling, preservation, storage .2
4.3 Interferences in photometry .2
5 Principle . 3
6 Reagents . 3
7 Apparatus . 6
8 Sampling, sample pretreatment and sample storage . 6
8.1 Sampling .6
8.2 Samples with reducing or oxidizing substances .7
8.3 Consideration of the self-absorption of coloured samples .7
8.4 Sample storage .7
9 Procedure . 7
9.1 General .7
9.2 Required concentrations of reagents in the reaction vessel .7
9.3 Required concentrations of reagents in the reaction vessel for measuring the intrinsic
absorption .8
9.4 Measurement .8
9.5 Calibration .8
9.6 Measurement of chromium(VI).8
9.7 Validity check of the calibration function .8
9.8 Calculation considering the ordinate intercept .9
9.9 Calculation offset when the photometer is zeroed .9
10 Expression of results . 10
11 Test report . 10
Annex A (normative) Manual static technique .11
Annex B (normative) Automated static techniques .12
Annex C (normative) Automated dynamic techniques .13
Annex D (normative) Calculations for adjusting reagent concentrations, volumes and flows .20
Annex E (informative) Performance data .23
Bibliography .26

iii
ISO/DIS 18724:2024(en)
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
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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).
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This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2,
Physical, chemical and biochemical methods.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 18724:2024(en)
Introduction
Chromium is an important raw material in the industrial manufacturing process that can contaminate
sources of drinking water (e.g. groundwater, surface water). The most common oxidation states of chromium
are +3 and +6. The hexavalent form (Cr(VI)) is far more toxic and water-polluting than the trivalent form
(Cr(III)).
The chromium content depends on several factors: the availability of chromium in the rock, the weathering
stage and the vicinity. Chromium(VI) occurs mainly in the aerobic environment; under reducing / anaerobic
conditions, chromium(VI) is reduced to chromium(III).
Chromium(VI) occurs naturally in groundwater aquifers, mostly in low concentrations depending on the
occurrence in geological formations, e.g., volcanic rocks.
Other sources of chromium(VI) contamination for the environment are industrial activities, e.g., the
production of textiles, leather tanning or electroplating.
A sensitive and specific photometric method for the determination of hexavalen
...