ISO 18917:1999

INTERNATIONAL ISO
STANDARD 18917
First edition
1999-06-01
Photography — Determination of residual
thiosulfate and other related chemicals in
processed photographic materials —
Methods using iodine-amylose, methylene
blue and silver sulfide
Photographie — Détermination du thiosulfate résiduel et d'autres produits
chimiques dans les produits photographiques traités — Méthodes à l'iode-
amylose, au bleu de méthylène et au sulfure d'argent
A
Reference number
Contents
1 Scope .1
2 Normative references .1
3 General requirements.2
4 Iodine-amylose method.3
5 Methylene blue method.7
6 Silver densitometric method .11
Annex A (informative) Appraisal of keeping characteristics .16
Annex B (informative) Guidance in the selection of test method.17
Annex C (informative) Preparation for 0,2 mol/l sodium hydroxide solution.18
Annex D (informative) Preparation of 1,000 mol/l sodium thiosulfate solution .19
Bibliography.21
©  ISO 1999
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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© ISO
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. Each 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 18917 was prepared by Technical Committee ISO/TC 42, Photography.
This first edition cancels and replaces the second edition of ISO 417 (ISO 417:1993) which has been technically
revised. As in the second edition, it includes the iodine-amylose and methylene blue procedures, but the reactant
levels have been modified to provide more reproducible results.
Annexes A, B, C and D of this International Standard are for information only.
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© ISO
Introduction
This International Standard is one of a series of specifications on photographic processing. Individuals without a
working knowledge of analytical chemistry may occasionally use this International Standard. Hazard warnings have
therefore been given using a system of symbols with letter codes designating the nature of the hazard. More
detailed information regarding hazards, handling and use of these chemicals may also be available from the
manufacturer.
Determination of residual thiosulfate and its decomposition products is of use in appraising the adequacy of washing
and therefore the permanence of the silver image on photographic films, plates and papers. Inadequate washing
can cause a loss in image density and the formation of stain in low-density areas. These deleterious effects are
accelerated by improper storage conditions.
Determination of residual thiosulfate and related compounds, by itself, is not sufficient to insure the permanence of
photographic records. Long term or archival storage requires proper attention to enclosure materials, storage
environment, and the like. These considerations are specified in ISO 3897, ISO 5466, ISO 6051 and ISO 10602.
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INTERNATIONAL STANDARD  © ISO ISO 18917:1999(E)
Photography — Determination of residual thiosulfate and other
related chemicals in processed photographic materials — Methods
using iodine-amylose, methylene blue and silver sulfide
1 Scope
1.1  This International Standard specifies test methods for the determination of residual thiosulfate and other
related chemicals in processed photographic materials.
1.2  This International Standard applies to silver halide/gelatin products that have been processed with a final
thiosulfate fixing bath and a water wash. This International Standard does not apply to stabilised black-and-white
products, thermally processed films, or instant-type products. The procedures given in this International Standard
measure residual thiosulfate, and the silver densitometric method measures residual related polythionate materials
as well. Measurements carried out by the procedures in this International Standard may, within the limitations stated
in annexes A and B, correlate with the image stabilities of processed photographs.
1.3  Film or plates with photographic-sensitive layers on both sides, or with a photographic sensitive layer on one
side and a gelatin backing layer on the reverse side, may contain approximately twice as much thiosulfate after
processing as samples having a coating on one side only. This situation will be true for materials for which residual
thiosulfate is determined by the iodine-amylose or methylene blue procedures.
NOTE For the method of reporting such results, see figure 1, example 2.
1.4  The iodine-amylose can be used with fibre-based paper, resin-coated paper, films and plates. It is the method
to be used with films and papers containing incorporated developing agents.
1.5  The methylene blue method can be used with fibre-based paper, resin-coated paper, films and plates but not
with films and paper containing incorporated developing agents.
1.6  The silver sulfide densitometric method measures thiosulfates, polythionates and all other residual chemicals
in a processed product that react with silver ion to form a silver "stain" under the conditions of the test.
1.7  A tabulated summary of methods, scope, etc. is given in annex B.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 5-3:1995, Photography — Density measurements — Part 3: Spectral conditions.
ISO 10349-1:1992, Photography — Photographic-grade chemicals — Test methods — Part 1: General.
© ISO
3 General requirements
3.1 Safety and hazard concerns
3.1.1 Handling
Reagents shall be handled in conformity with health and safety precautions as shown on containers or as given in
other sources of such information. Proper labelling of prepared reagents includes chemical name, date of
preparation, expiration date, restandardization date, name of preparer, and adequate health and safety precautions.
The discharge of reagents shall conform to applicable environmental regulations.
3.1.2 Hazard warnings
Some of the chemicals specified in the test procedures are caustic, toxic or otherwise hazardous. 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. Specific danger notices are given in the text for
particularly dangerous materials, but normal precautions are required during the performance of any chemical
procedure at all times.
The first time that a hazardous is noted in the test procedure, the hazard shall be indicated by the word “DANGER”
followed by a symbol consisting of angle brackets "Æ æ" containing a letter which designates the specific hazard. A
double bracket " " shall be used for particularly perilous situations.
In subsequent statements involving handling of these hazardous materials, only the hazard symbol consisting of the
brackets and letter(s) shall be displayed. Furthermore, for a given material, the hazard symbols shall be used only
once in a single paragraph.
Detailed warnings for handling chemicals and their diluted solutions are beyond the scope of this International
Standard.
Employers shall provide training and health and safety information in conformance with legal
requirements.
The hazard symbol system used in this International Standard is intended to provide information to the users and is
not meant for compliance with legal requirements for labelling, as these vary from country to country.
It is strongly recommended that anyone using these chemicals obtain from the manufacturer pertinent
information about the hazards, handling, use and disposal of these chemicals.
3.1.3 Hazard information code system
ÆBæHarmful if inhaled. Avoid breathing dust, vapour, mist or gas. Use only with adequate ventilation.
ÆCæHarmful if contact occurs. Avoid contact with eyes, skin or clothing. Wash thoroughly after handling.
ÆSæHarmful if swallowed. Wash thoroughly after handling. If swallowed, obtain medical attention immediately.
S May be fatal if swallowed. If swallowed, obtain medical attention immediately.
ÆFæWill burn. Keep away from heat, sparks, and open flame. Use with adequate ventilation.
ÆOæOxidizer. Contact with other material may cause fire. Do not store near combustible materials.
The flammable warning symbol, ÆFæ, shall not be used for quantities of common solvents under 1 litre.
ææ ÆÆ
ææ ÆÆ
© ISO
3.2 Reagents
Reagents used in the test procedures shall be certified reagent-grade chemicals and shall meet appropriate
standards or be chemicals of purity acceptable for the analysis.
NOTE Further details are given in ISO 6353-1, ISO 6353-2 and ISO 6353-3 (see bibliography).
Whenever water is specified without other qualifiers in the test procedures, only distilled water or water of at least
equal purity shall be used.
3.3 Glassware
1)
All glassware subject to heating shall be of heat-resistant borosilicate glass.
Pipettes and other volumetric glassware shall meet the volume requirements of Class A or Class B glassware as
specified in ISO 10349-1.
4 Iodine-amylose method
4.1 Use
The iodine-amylose method is applicable to the determination of residual thiosulfate ions in film and resin-coated
photographic paper containing incorporated developing agents. The procedure covers the range from 0,002 mg/cm
to 0,40 mg/cm . The method is also applicable to measuring residual thiosulfate ion in fibre-based paper, film and
plates. This method measures only thiosulfate ions and gives results comparable to those obtained by the
methylene blue method.
The method gives results that correlate well with accelerated keeping tests of several processed microfilms and is
applicable to colour as well as black-and-white products.
4.2 Principle
The eluent (4.4.4) is added to the sample to extract residual thiosulfate, tetrathionate and pentathionate ions.
Formalin is added to form a complex with any sulfite ion present. Iodine is added to an amylose (fractionated linear
potato starch) indicator to form a blue-coloured solution. The thiosulfate in the eluent, when added to the iodine-
amylose solution, will react with the iodine and proportionately reduce the intensity of the blue colour. The loss in
colour corresponds to the thiosulfate concentration.
4.3 Chemical reactions
a) Starch (C H O ) + I (in KI solution)  fi  Blue-coloured solution
6 10 5 n 2
2-
b) Blue-coloured solution +  fi  Decrease in blue colour intensity
SO
4.4 Reagents
4.4.1 Potassium iodate, c(KIO ) = 0,000 017 mol/l (0,003 57 g/l)
Prepare a 0,0167 mol/l solution of potassium iodate by weighing 0,357 g of potassium iodate (DANGER:ÆOæ) and
placing it in a 100 ml one-mark volumetric flask, making up to the mark with water and mixing well. Pipette 1,0 ml of
the 0,016 7 mol/l potassium iodate solution into a 1 litre one-mark volumetric flask, making up to the mark with
water.
1)
PyrexÒ is an example of suitable glassware available commercially. This information is given for the convenience of users of

this International Standard and does not constitute an endorsement by ISO of this brand.
© ISO
4.4.2 Formate buffer, pH 2,0
Add, from a graduated cylinder, 110 ml of formic acid (HCO H)) (88-90 %) (DANGER: ÆCæ ÆBæ ÆSæ ÆFæ) to a 1 litre
one-mark volumetric flask containing 500 ml to 600 ml of water, and make up to the mark with water. Using a pH
meter, adjust the solution to pH 2,0 ± 0,1 at 21 °C with 10 mol/l sodium hydroxide solution (4.4.8) (DANGER: C )
from a dropping pipette.
4.4.3 Formate buffer, pH 2,8
Pipette 10,0 ml of pH 2,0 formate buffer (4.4.2) into a 1 litre one-mark volumetric flask and make up to the mark with
water.
4.4.4 Eluent
Dissolve 1,0 g ± 0,1 g of potassium iodide (KI)
...