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International
Standard
ISO 10714
Second edition
Steel and iron — Determination
2024-07
of phosphorus content —
Phosphovanadomolybdate
spectrophotometric method
Aciers et fontes — Détermination des teneurs en phosphore —
Méthode spectrophotométrique au phosphomolybdovanadate
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 3
7 Sampling and sample preparation . 4
8 Procedure . 4
8.1 Test portion .4
8.2 Blank test .4
8.3 Determination .4
8.3.1 Preparation of the test solution .4
8.3.2 Colour development and extraction .5
8.3.3 Spectrophotometric measurements .5
8.4 Establishment of the calibration curve .5
8.4.1 Preparation of calibration solutions .5
8.4.2 Spectrophotometric measurements .6
8.4.3 Plotting the calibration curve .6
9 Expression of results . 6
9.1 Method of calculation .6
9.2 Precision . . .6
10 Test report . 7
Annex A (informative) Additional information on the international interlaboratory test . 8
Annex B (informative) Graphical presentation of precision data . 9
Bibliography .10
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
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This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 1, Methods of
determination of chemical composition, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 459, ECISS - European Committee for Iron and Steel Standardization, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 10714:1992), which has been technically
revised.
The main changes are as follows:
— a complete revaluation of the precision data.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
International Standard ISO 10714:2024(en)
Steel and iron — Determination of phosphorus content —
Phosphovanadomolybdate spectrophotometric method
1 Scope
This document specifies a spectrophotometric method for the determination of phosphorus in steel and
cast iron.
The method is applicable to phosphorus contents between 0,001 0 % (mass fraction) and 1,0 % (mass
fraction).
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 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical composition
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
Dissolution of a test portion in an oxidizing acid mixture.
Fuming with perchloric acid and removal of chromium as volatile chromyl chloride.
Complexing of silicon and the refractory elements with hydrofluoric acid and complexing of the excess of
hydrofluoric acid with orthoboric acid.
Conversion of phosphorus to phosphovanadomolybdate in presence of perchloric and nitric acids.
Extraction of phosphovanadomolybdate by 4-methyl-2-pentanone in presence of citric acid to complex
arsenic.
Spectrophotometric measurements at a wavelength of 355 nm.
Arsenic, hafnium, niobium, tantalum, titanium and tungsten interfere in determining phosphorus, but
the interferences can be partially overcome by formation of complexes and use of small quantities of test
portion. Depending on the content of the interfering elements, the application ranges and test portions given
in Table 1 apply.
The lower end of the application range can only be reached in test samples with low content of the interfering
elements.
Table 1 — Application ranges and test portions
Maximum content of the interfering elements
Application range,
Test portion
% (mass fraction) Δw
p
g
% (mass fraction)
As Hf Nb Ta Ti W
0,05 0,1 1 0,1 2 2 1,0 0,001 to 0,010
0,2 0,5 5 0,5 10 8 0,25 0,005 to 0,040
0,5 1,5 10 1,0 25 25 0,10 0,010 to 0,100
0,2 0,5 5 0,5 10 8 0,25 0,100 to 1,00
5 Reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only
grade 2 water as specified in ISO 3696.
Verify by blank tests (8.2) that the reagents are free from phosphorus or of very low phosphorus content.
Whenever necessary, the results shall be corrected accordingly. Reagents giving high blank values (above
10 µg) are unsuitable and shall be discarded.
5.1 Hydrochloric acid, ρ about 1,19 g/ml.
5.2 Nitric acid, ρ about 1,40 g/ml.
5.3 Nitric acid solution, ρ about 1,40 g/ml, diluted 1 + 4.
5.4 Perchloric acid, ρ about 1,54 g/ml.
WARNING — Perchloric acid vapour can cause explosions in the presence of ammonia, nitrous fumes
or organic material in general.
5.5 Hydrofluoric acid, ρ about 1,14 g/ml.
5.6 Citric acid, 500 g/l.
Dissolve 500 g of citric acid monohydrate (H C O ·H O) in water, dilute to 1 000 ml with water and mix.
8 6 7 2
5.7 4-Methyl-2-pentanone (isobutyl methyl ketone).
The same batch of 4-methyl-2-pentanone shall be used for analysing a series of samples.
5.8 Hexa-ammonium heptamolybdate, 150 g/l.
Dissolve 150 g of hexa-ammonium heptamolybdate tetrahydrate [(NH ) Mo O ·4H O] in water, dilute to
4 6 7 24 2
1 000 ml with water and mix.
This solution shall be freshly prepared each day.
High and unstable blank values might be attributed to this reagent in particular. In such a case, change to
another batch.
5.9 Ammonium metavanadate, 2,5 g/l.
Dissolve 2,5 g of ammonium metavanadate (NH VO ) in water, dilute to 1 000 ml with water and mix.
4 3
5.10 Sodium nitrite, 50 g/l.
Dissolve 50 g of sodium nitrite (NaNO ) in water, dilute to 1 000 ml with water and mix.
5.11 Tetrafluoroboric acid.
Dissolve 75 g of orthoboric acid (H BO ) in 600 ml of water in a plastic beaker. Add 50 ml of hydrofluoric
3 3
acid (5.5), dilute to 1 000 ml with water and mix. The solution can be gently heated if the boric acid tends to
precipitate.
Keep the solution in a plastic bottle.
5.12 Phosphorus, standard solutions.
5.12.1 Phosphorus standard solution, 1 g/l.
Weigh, to the nearest 0,000 1 g, 4,393 6 g of potassium dihydrogen phosphate (KH PO ) previously dried to
2 4
constant mass at 110 °C and cooled in a desiccator.
Transfer into a 1 000 ml one-mark volumetric flask, dissolve in water, dilute to the mark with water and mix.
1 ml of this standard solution contains 1 mg of phosph
...