IS 2211 : 2024/ISO 10636 : 1994 Sodium Thiosulphate, Anhydrous and Pentahydrate, Photographic Grade - Specification

ICS 37.040.30

CHD 05

(Superseding IS 246 : 1986)

NATIONAL FOREWORD

This Indian Standard (Third Revision), which is identical to ISO 10636 : 1994 'Photography - Processing chemicals - Specifications for anhydrous sodium thiosulfate and sodium thiosulfate pentahydrate' issued by the International Organization for Standardization (ISO), was adopted by the Bureau of Indian Standards, on the recommendation of Electroplating Chemicals and Photographic Materials Sectional Committee and approval of the Chemical Division Council.

BIS has published 2 Indian Standards on Sodium thiosulphate, photographic grade IS 246 : 1986 and IS 2211 : 1993.

IS 246 was first published in 1950 and subsequently revised in 1957, 1964, 1972 and 1986 under the title eSpecification for Sodium Thiosulphate, crystalline, photographic gradef. Sodium thiosulphate, crystalline with the formula Na.S.O..5H2O is commonly known as hypo and is used in the photographic industry as a fixing agent to dissolve unchanged silver salts from exposed negatives. In the fourth revision of this standard, the limits for heavy metals and iron were modified.

IS 2211 was first published in 1962 and subsequently revised in 1972 and 1993 under the title eAnhydrous Sodium Thiosulphate, photographic grade - Specificationf. Sodium thiosulfate, anhydrous is an inorganic compound with the chemical formula Na.S.O. and relative molar mass 158.1. In the second revision, the requirements of pH and heavy metals were modified. Changes were also made in the methods for determination of sodium thiosulphate, pH and sulphide.

The Committee responsible for formulation of these standards decided to revise IS 2211 by adopting ISO 10636 : 1994 ePhotography . Processing chemicals . Specifications for anhydrous sodium thiosulfate and sodium thiosulfate pentahydratef on dual number basis. This revision is being undertaken by amalgamating IS 246 and IS 2211 and will be published as third revision of IS 2211 and subsequent to this publication IS 246 will be superseded.

ISO 10636 specifies the requirements of both grades of sodium thiosulphate i.e. anhydrous and pentahydrate. Accordingly the title of this standard is being modified to 'Sodium Thiosulphate, Anhydrous and Pentahydrate, Photographic Grade - Specification'.

The text of the ISO standard has been approved as suitable for publication as an Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:

a) Wherever the words 'International Standard' appear referring to this standard, they should be read as 'Indian Standard'; and

b) Comma (,) has been used as a decimal marker, while in Indian Standards the current practice is to use a point (.) as the decimal marker.