ISO 3626:1996 pdf download – Photography – Processing chemicals – Specifications for potassium thiocyanate
I Scope
This International Standard establishes criteria for the purity of photographic-grade potassium thiocyanate and specifies the test methods to be used to determine the purity.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 10349-I : 1992, Photography – Photographic-grade chemicals – Test methods – Part I: General.
ISO 10349-5: 1992, Photography – Photographic-grade chemicals – Test methods – Part 5: Determination of heavy metals and iron con tent.
ISO 10349-6: 1992, Photography – Photographic-grade chemicals – Test methods – Part 6: Determination of halide con tent.
3 General
3.1 Physical properties
Potassium thiocyanate (KCNS) exists as colourless, deliquescent crystals. It has a relative molecular mass of 97,18.
3.2 Hazardous properties
Potassium thiocyanate presents no special hazardous problems under normal handling.
3.3 Storage
Store in a cool dry place. Care shall be taken to avoid conditions of high heat and/or humidity which can cause decomposition and emission of toxic fumes.
4 Requirements
A summary of the requirements is shown in table 1.
5 Reagents and materials, including glassware
All reagents, materials and glassware shall conform to the requirements specified in ISO 10349-I unless otherwise noted. The hazard warning symbols used as a reminder in those steps detailing handling operations are defined in IS0 10349-I. These symbols are used to provide information to the user and are not meant to provide conformance with hazardous labelling requirements, as these vary from country to country.
6 Sampling
See ISO 10349-I.
7 Test procedures
7.1 Assay
7.1.1 Specification
Content of KCNS shall be 98,0 % (m/m) min.
7.1.2 Reagents
7.1.2.1 Nitric acid (HNO$, (I + 9) solution 1).
7.1.2.2 Ammonium iron(W) sulfate [(NHa)Fe(SO&], 50 g/l solution.
7.1.2.3 Silver nitrate (AgNO$, standard volumetric solution of 0,100 mol/l (17,O g/l) 2) 3).
7.1.2.4 Ammonium thiocyanate (NHaSCN), standard volumetric solution of 0,100 mol/l (7,61 g/l) 2).
7.1.3 Apparatus
7.1.3.1 Burette, of 50 ml capacity.
7.1.3.2 Pipette, of 50 ml capacity.
7.1.4 Procedure
Weigh, to the nearest 0,001 g, a test portion of about 0,3 g and dissolve it in 50 ml of water. Add 5 ml of the nitric acid (7.1.2.1), followed by 50,OO ml of the silver nitrate (7.1.2.3) using the pipette (7.1.3.2). Shake well, add 2 ml of the ammonium iron(lll) sulfate (7.1.2.2) and titrate the excess of silver nitrate with the ammonium thiocyanate (7.1.2.4) to a permanent red endpoint.