ISO 420:1994

INTERNATIONAL ISO
STANDARD
420
Second edition
1994-1 o-1 5
Photography - Processing chemicals -
Specifications for potassium bromide
Photographie - Produits chimiques de traitement - Spkcifications pour Ie
bromure de potassium
Reference number
ISO 420: II 994(E)

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ISO 420: 1994(E)
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. Esch 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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 420 was prepared by Technical Committee
lSO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 420:1976),
which has been technically revised.
0 ISO 1994
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microfilm, without permrssion in writing from the publisher.
lnternational Organization for Standardization
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Printed in Switzerland

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0 ISO ISO 420: 1994(E)
Introduction
0.1 This International Standard is one of a series that establishes criteria
of purity for chemicals used in processing photographic materials. General
test methods and procedures cited in this International Standard are
compiled in Parts 1, 3, 5, 6, 7, 8 and 10 of ISO 10349.
This International Standard is intended for use by individuals with a
working knowledge of analytical techniques, which may not always be the
case. Some of the procedures utilize caustic, toxic or otherwise hazardous
chemicals. Safe laboratory practice for the handling of chemicals requires
the use of safety glasses or goggles, rubber gloves and other protective
apparel such as face masks or aprons where appropriate. Normal
precautions required in the Performance of any Chemical procedure are to
be exercised at all times but care has been taken to provide warnings for
hazardous materials. Hazard warnings designated by a letter enclosed in
angle brackets, < >, are used as a reminder in those Steps detailing
handling operations and are defined in ISO 10349-1. More detailed
information regarding hazards, handling and use of these chemicals may
be available from the manufacturer.
0.2 This International Standard provides Chemical and physical re-
quirements for the suitability of a photographit-grade Chemical. The tests
correlate with undesirable photographic effects. Purity requirements are
set as low as possible consistent with these photographic effects. These
criteria are considered the minimum requirements necessary to assure
sufficient purity for use in photographic processing solutions, except that if
the purity of a commonly available grade of Chemical exceeds photographic
processing requirements and if there is no economic penalty in its use, the
purity requirements have been set to take advantage of the availability of
the higher-quality material. Every effort has been made to keep the
number of requirements to a minimum. Inert impurities are limited to
amounts which will not unduly reduce the assay. All tests are performed
on samples “as received” to reflect the condition of materials furnished for
use. Although the ultimate criterion for suitability of such a Chemical is its
successful Performance in an appropriate use test, the shorter, more
economical test methods described in this International Standard are
generally adequate.
Assay procedures have been included in all cases where a satisfactory
method is available. An effective assay requirement serves not only as a
safeguard of Chemical purity but also as a valuable complement to the
identity test. Identity tests have been included whenever a possibility
exists that another Chemical or mixture of chemicals could pass the other
tests.
All requirements listed in clause 4 are mandatory. The physical appearance
of the material and any footnotes are for general information only and are
not part of the requirements.
. . .
Ill

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0 ISO
ISO 420:1994(E)
0.3 Efforts have been made to employ tests which are capable of being
run in any normally equipped laboratory and, wherever possible, to avoid
tests which require highly specialized equipment or techniques. Instru-
mental methods have been specified only as alternative methods or alone
in those cases where no other satisfactory method is available.
Over the past few years, great improvements have been made in instru-
mentation for various analyses. Where such techniques have equivalent or
greater precision, they may be used in place of the tests described in this
International Standard. Correlation of such alternative procedures with the
given method is the responsibility of the User. In case of disagreement in
results, the method called for in the specification shall prevail. Where a
requirement states “to pass test ”, however, alternative methods shall not
be used.

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ISO 420: 1994(E)
INTERNATIONAL STANDARD o Iso
Photography - Processing chemicals - Specifications for
potassium bromide
3 General
1 Scope
3.1 Physical properties
This International Standard establishes criteria for the
purity of photographit-grade potassium bromide and
Potassium bromide (KBr) exists in the form of white
specifies the test methods to be used to determine
crystals or a crystalline powder. lt has a relative
the purity.
molecular mass of 119,OO.
3.2 Hazardous properties
2 Normative references
Potassium bromide is not hazardous when handled
The following International Standards contain pro-
with normal precautions.
visions which, through reference in this text, consti-
tute provisions of this International Standard. At the
time of publication, the editions indicated were valid.
3.3 Storage
All Standards are subject to revision, and Parties to
agreements based on this International Standard are Potassium bromide shall be stored in a closed
encouraged to investigate the possibility of applying Container at room temperature.
the most recent editions of the Standards indicated
below. Members of IEC and ISO maintain registers of
currently valid International Standards
4 Requirements
A summary of the requirements is shown in table 1.
ISO 10349-1: 1992, Photography - Photographic-
grade chemicals - Test methods - Part 1: General.
5 Reagents and glassware
ISO 10349-3: 1992, Photography - Photographic-
grade chemicals - Test methods - Part 3: Determi-
All reagents, materials and glassware shall conform to
nation of matter insoluble in ammonium hydroxide
the requirements specified in ISO 10349-1 unless
solution.
otherwise noted. The hazard warning Symbols used
as a reminder in those Steps detailing handling
ISO 10349-5: 1992, Photography - Photographic- operations are defined in ISO 10349-1. These Symbols
grade chemicals - Test methods - Part 5: Determi- are used to provide information to the user and are
nation of heavy metals and iron content. not meant to provide conformance with hazardous
labelling requirements, as these vary from country to
country.
ISO 10349-6: 1992, Photography - Photographic-
grade chemicals - Test methods - Part 6: Determi-
nation of halide con tent.
6 Sampling
ISO 10349-7: 1992, Photography - Photographic-
See ISO 10349-1.
grade chemicals - Test methods - Part 7: Determi-
nation of alkalinity or acidity.
7 Test methods
ISO 10349-8: 1992, Photography - Photographic-
7.1 Assay
grade chemicals - Test methods - Part 8: Determi-
nation of volatile matter.
7.1.1. Specification
ISO 10349-10: 1992, Photography - Photographic-
Content of KBr shall be between 99,0 % (m/m) min.
grade chemicals - Test methods - Part IO: Determi-
and 100,3 % (mlm) max.
nation of sulfide tonten t.
1

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ISO 420:1994(E)
0 ISO
Table 1 - Summary of requirements
International
Standard in
Test Limit Subclause
which test
method is given
Assay
99,0 % (HZ/IPZ) min. 7.1 ISO420
100,3 % (m/m) max.
Insoluble matter (as
0,3 % (mlm) max. 7.2 ISO 10349-3
precipitate of Calcium and
magnesium in
ammonium hydroxide)
Heavy metals (as Pb) 0,002 % (~-TZ/ITZ) max. 7.3 ISO 10349-5
Iron (Fe) 0,002 % (ITZ/UZ) max. ISO 10349-5
7,4
Halides (as KCI)
0,50 % (m/m) max. 7.5 ISO 10349-6
Alkaiinity (as KOH) 0,015 % (m/m) max. 7.6 ISO 10349-7
Acidity (as HBr) 0,010 % (m/m) max. 7.7
...