ISO 622:2016

INTERNATIONAL ISO
STANDARD 622
Second edition
2016-11-15
Solid mineral fuels — Determination
of phosphorus content — Reduced
molybdophosphate photometric
method
Combustibles minéraux solides — Dosage du phosphore — Méthode
photométrique au molybdophosphate réduit
Reference number
ISO 622:2016(E)
©
ISO 2016

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ISO 622:2016(E)

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ii © ISO 2016 – All rights reserved

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ISO 622:2016(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Extraction . 1
4.2 Determination . 1
5 Reagents . 2
6 Apparatus . 2
7 Sample preparation . 3
8 Procedure. 3
8.1 Dry oxidation method . 3
8.2 Wet oxidation method . 4
8.3 Determination . 5
9 Expression of results . 5
9.1 Method of calculation and formulae . 5
10 Precision of the method . 6
10.1 Repeatability . 6
10.2 Reproducibility . 6
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ISO 622:2016(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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The committee responsible for this document is ISO/TC 27, Solid minerals fuels, Subcommittee SC 5,
Methods of analysis.
This second edition cancels and replaces the first edition (ISO 622:1981), which has been technically
revised. This document incorporates changes related to references and other minor items following its
systematic review.
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INTERNATIONAL STANDARD ISO 622:2016(E)
Solid mineral fuels — Determination of phosphorus content
— Reduced molybdophosphate photometric method
1 Scope
This document specifies a reduced molybdophosphate photometric method for the determination of the
total phosphorus content of hard coal, lignites and coke. Two methods for taking the phosphorus into
solution are specified, namely extraction from the coal or coke ash with acid or by repeated oxidation of
the coal or coke, by acid, to remove carbonaceous matter.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 383, Laboratory glassware — Interchangeable conical ground joints
ISO 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes
of openings
ISO 1171, Solid mineral fuels — Determination of ash
ISO 18283, Hard coal and coke — Manual sampling
3 Terms and definitions
No terms and definitions are defined in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
4 Principle
4.1 Extraction
Method 1: Removal of carbonaceous material by ashing in a muffle furnace under specified conditions,
and extraction of phosphorus by treatment with hydrofluoric and sulphuric acids.
Method 2: Removal of carbonaceous material by repeated oxidation with nitric acid in the presence of
sulphuric acid.
4.2 Determination
Addition of ammonium molybdate and ascorbic acid solution to the acid solution. Measurement of the
absorbance of the resulting blue solution by a suitable optical instrument.
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ISO 622:2016(E)

5 Reagents
During the analysis, use only reagents of recognized analytical grade and only distilled water or water
of equivalent purity.
5.1 Hydrofluoric acid, approximately 400 g/l solution.
WARNING — Aqueous hydrofluoric acid is a highly corrosive liquid which attacks glass; the
vapour is irritant and toxic. Its action on the skin and eyes is strongly corrosive, producing
severe and painful burns which may not be immediately evident and which respond slowly to
treatment. The solution should be handled only inside a well-ventilated fume cupboard. In the
event of contact or suspected contact, flood with water and seek immediate medical attention.
The manufacturer’s literature should be consulted for further information.
5.2 Sulphuric acid, approximately 490 g/l solution.
5.3 Sulphuric acid, concentrated, ρ 1,84 g/ml, approximately 98 % (m/m) solution.
5.4 Nitric acid, concentrated, ρ 1,42 g/ml, approximately 70 % (m/m) solution.
5.5 Ammonium molybdate, 60 g/l solution.
5.6 Ascorbic acid, 50 g/l solution.
Prepare the solution fresh daily.
5.7 Antimony potassium tartrate (KSbO·C H O ), 1,36 g/l solution.
4 4 6
5.8 Reagent solution.
Mix 25 ml of the sulphuric acid solution (5.2), 10 ml of the
...