ISO 3627:1994

INTERNATIONAL
ISO
STANDARD
3627
Second edition
1994-11-01
Photography - Processing chemicals -
Specifications for anhydrous sodium
metabisulfite
Pho tographie - Produits chimiques de traitement - Spkifications pour Ie
m&adisulfite de sodium anhydre
Reference nurher
ISO 3627:1994(E)

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ISO 3627: 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 lnternationai 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 3627 was prepared by Technical Committee
lSO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 3627:I 976),
which has been technically revised.
0 ISO 1994
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microfilm, without Permission in writing from the publisher.
International ization for Standardization
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Printed in Switzerland

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0 ISO ISO 3627:1994(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, 5 and 9 of ISO 10349.
This International Standard is intended for use by individuals with a
working knowledge of analytical techniques which is possibly not always
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
should 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 require-
ments 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.

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ISO 3627: 1994(E) 0 ISO
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.
Instrumental 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
instrumentation 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 Yo pass test ”, however, alternative
methods shall not be used.

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INTERNATIONAL STANDARD o ISO
ISO 3627: 1994(E)
Photography - Processing chemicals
- Specifications for
anhydrous sodium metabisulfite
1 Scope
ISO 10349-9: 1992, Photography - Photographic-
grade chemicals - Test methods - Part 9: Reaction
This International Standard establishes criteria for the to ammoniacal Siber nitrate.
purity of photographit-grade anhydrous sodium
metabisulfite and describes the tests to be used to
3 General
determine the purity.
3.1 Physical properties
2 Normative references
Anhydrous sodium metabisulfite, Na2S205, exists as a
white or pale cream granular powder. lt has a relative
The following International Standards contain pro-
molecular mass of 190,lO.
visions which,
through reference in this text,
constitute provisions of this International Standard. At
3.2 Hazardous properties
the time of publication, the editions indicated were
valid. All Standards are subject to revision, and Parties
Anhydrous sodium metabisulfite is not hazardous
PO agreements based on this International Standard
when handled with normal precautions. Avoid contact
are encouraged to investigate the possibility of
with acids.
applying the most recent editions of the Standards
indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
3.3 Storage
ISO 10349-1: 1992, Photography - Photographic- Anhydrous sodium metabisulfite shall be stored in a
grade chemicals - Test methods - Part 7: General.
closed Container at room temperature.
ISO 10349-5: 1992, Photography - Photographic-
4 Requirements
grade chemicals - Test methods - Part 5: Determi-
na tion of heavy metals and iron tonten t. A summary of the requirements is shown in table 1.
Table 1 - Summary of requirements
International Standard in
Test Limit Subclause
which test method is given
Assay 95,0 % (WZ/WZ) min. 7.1 ISO 3627
Heavy metals content (as Pb) 0,005 % (m/m) max. 7.2
ISO 10349-5
Iran content (Fe) 0,005 % (m/m) max. 7.3
ISO 10349-5
Reaction to ammoniacal silver nitrate To pass test 7.4 ISO 10349-9
pH value 3,7 to 4,6 7.5
ISO 3627
2-
Thiosulfate content (as SZ03 ) 0,03 % (m/m) max. 7.6
ISO 3627
Appearance of solution Clear and free from 7.7
ISO 3627
insoluble matter except
for a slight flocculence
NOTE - m/m = mass/mass.
1

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ISO 3627: 1994(E)
0 ISO
5 Reagents and glassware 7.1.2.5 Salicylic acid, HOCGH4COOH, 1 % (IO g/l).
All reagents, materials and glassware shall conform to
7.1.2.6 Starch indicator .
5 g/l
the requirements specified in ISO 10349-1 unless
otherwise noted. The hazard warning Symbols used
Stir 5 g of soluble starch into 100 ml of the salicylic
as a reminder in those Steps detailing handling oper-
acid (7.1 J.5). Add 300 m to 400 ml of boiling water
ations are defined in ISO 10349-1. These Symbols are
and boil until the starch
dissolves. Finally dilute to
used to provide information to the user and are not
1 litre with water.
meant to provide conformance with hazardous
labelling requirements as these vary from country to
7.1.2.7 Sodium thiosulfate, Na2S203, Standard
country.
volumetric Solution of 0,100 mol/1 (15,8 g/l)2).
6 Sampling
7.1.2.8 Sulfuric acid, H2S04, Standard volumetric
Solution of 0,05 mol/1 (4,9 g/l)2)4).
See ISO 10349-1.
7.1.2.9 Phenolphthalein indicator, 5 g/l.
7 Test methods
Dissolve 1 g of phenolphthalein in 100 ml of ethanol
(7.1.2.11) and add 100 ml of water with constant
7.1 Assay
stirring. Filter if necessary.
7.1 .l Specification
7.1.2.10 Hydrochlorit acid, HCI, p= 1,18 g/ml
(DANGER: ).
Content of sodium metabisulfite shall be 95,0 % (~/vz)
min.
7.1.2.11 Ethanol, C2H50H, 95 % (denatured).
7.1.2 Reagents
7.1.3 Apparatus
7.1.2.1 Acetic acid, glacial, CH,COOH
(DANGER:) ‘).
7.1.3.1 Burette, of 50 ml capacity.
7.1.2.2 Acetic acid, 2 mol/1 approximately).
7.1.3.2 Pipette, of 50 ml capacity.
Dilute 120 g of glacial acetic acid (7.1.2.1) ()
to 1 litre.
7.1.3.3 Magnetit stirrer and bar (for direct-titration
method).
7.1.2.3 Formaldehyde, HCHO, neutral, 37 %,
360 g/l (approximately) (DANGER: ).
7.1.4 Procedure
Adjust the pH of the formaldehyde Solution so that it
Use either the back-titration method (7.1.4.1) or the
is neutral to phenolphthalein indicator (7.1.2.9).
direct-titration method (7.1.4.2).
7.1.2.4 lodine, 12, Standard volume
...