ISO 20258:2018

INTERNATIONAL ISO
STANDARD 20258
First edition
2018-08
Magnesium lithium alloys —
Determination of lithium —
Inductively coupled plasma optical
emission spectrometric method
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 2
7 Sampling and sample preparation . 3
8 Procedure. 3
8.1 General . 3
8.2 Test portion . 4
8.3 Determination . 4
8.3.1 Preparation of the test solution . 4
8.3.2 Preparation of the calibration solutions . 4
8.4 Adjustment of the apparatus . 4
8.5 Measurement of the calibration solutions . 4
8.6 Calibration curve . 5
8.7 Measurements of the test solution . 5
9 Expression of results . 5
9.1 Method of calculation . 5
9.2 Precision . 5
10 Test report . 6
Annex A (normative) Inductively coupled plasma optical emission spectrometer —
Performance criteria to be checked . 7
Annex B (informative) Information on the precision test . 9
Annex C (informative) Graphical representation of precision data .10
Bibliography .11
Foreword
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This document was prepared by Technical Committee ISO/TC 79, Light metals and their alloys,
Subcommittee SC 5, Magnesium and alloys of cast or wrought magnesium.
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iv © ISO 2018 – All rights reserved

Introduction
Magnesium lithium alloys are the lightest metallic materials in the world and show several
advantageous properties such as: excellent rigidity, high electric and thermal conductivity, good
damping, electromagnetic, shielding, welding, matching and cold forming performances. Lithium is the
most important element in magnesium lithium alloys, and can improve the deformation capability of
alloys with further a decrease in weight. With the increasing demands of the world today for lightweight
materials, energy saving, environmental protection and sustainable development, magnesium lithium
alloys show broad application prospects in the fields of materials, transportation, electronics, medical
products and so on.
Chemical compositions of magnesium and its alloys are widely standardized from major to trace
contents in international and other national standards. However, there is no standard dealing with the
determination of lithium content in magnesium lithium alloys.
INTERNATIONAL STANDARD ISO 20258:2018(E)
Magnesium lithium alloys — Determination of lithium
— Inductively coupled plasma optical emission
spectrometric method
1 Scope
This document specifies a method for the determination of lithium contents in magnesium lithium
alloys by inductively coupled plasma (ICP) optical emission spectrometry.
The method is applicable to the determination of lithium content between 3,0 % and 16,0 % (mass
fraction) in magnesium lithium alloys.
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
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
Dissolution of a test portion in hydrochloric acid. Nebulization of the solution into an ICP optical
emission spectrometer and measurement of the intensity of the emitted light from lithium.
Calibration based on a very close matrix matching of the calibration solutions to the sample shall be
carried out. The advantage with this procedure is that all possible interferences from the matrix will be
compensated, which will result in high accuracy. This is important to spectral interferences, which can
be severe in highly alloyed matrixes.
All spectral interferences shall be kept at a minimum level. Therefore, it is essential to select the
appropriate wavelengths. The wavelengths generally used for lithium are shown in Table 1 together
with the possible interferences. Depending on the performance of each spectrometer, other wavelengths
may be used, provided that interferences, sensitivity, resolution and linearity criteria have been
carefully investigated.
5 Reagents
During the analysis, use only reagents of recognized analytical grade and only grade 2 water as
specified in ISO 3696, or water of equivalent purity.
5.1 Pure magnesium, purity ≥ 99,99 % (mass fraction), free from lithium.
5.2 Lithium carbonate, purity ≥ 99,99 % (mass fraction).
5.3 Hydrochloric acid, ρ about 1,19 g/ml.
5.4 Hydrochloric acid solution 1 + 1, add 500 ml of hydrochloric acid (5.3) to 500 ml of water.
5.5 Hydrogen peroxide, ρ about 1,13 g/ml.
5.6 Magnesium base solution, corresponding to 2,5 g of magnesium per litre.
Weigh, to the nearest of 1 mg, 0,5 g of pure magnesium (5.1) and transfer into a 300 ml glass beaker.
Add about 50 ml of water and, in small portions, 25 ml of hydrochloric acid (5.4). Cover with a watch-
glass and, if necessary, heat gently to complete the dissolution. Add a few drops of hydrogen peroxide
(5.5) and boil for 5 min. Cool and transfer quantitatively into a 200 ml one-mark volumetric flask. Dilute
to the mark with water and mix.
1 ml of this solution contains 2,5 mg of magnesium.
5.7 Magnesium base solution, corresponding to 0,25 g of magnesium per litre.
Transfer 10 ml of the solution (5.6) to a 100 ml one-mark volumetric flask. Add 10 ml of hydrochloric
acid (5.4). Dilute to the mark with water and mix.
1 ml of this solution contains 0,25 mg of magnesium.
5.8 Lithium standard solution, corresponding to 1,0 g of lithium per litre.
Dry several grams of lithium carbonate (5.2) in an oven at 100 °C ± 5 °C for at least 1 h and cool to room
temperature in a desiccator. Weigh, to the nearest 0,1 mg, 5,322 8 g of the dried lithium carbonate,
transfer into a 500 ml glass beaker, add 60 ml of hydrochloric acid (5.4), cover with a watch-glass and, if
necessary, heat gently to complete the dissolution. Cool and transfer quantitatively into a 1 000 ml one-
mark volumetric flask. Dilute to the mark with water and mix.
1 ml of this solution contains 1,0 mg of lithium.
5.9 Lithium standard solution, corresponding to 0,1 g of lithium per litre.
Transfer 10,00 ml of the lithium standard solution (5.8) to a one-mark 100 ml volumetric flask. Add
10 ml of hydrochloric acid (5.4). Dilute to the mark with water and mix.
1 ml of this solution contains 0,1 mg of lithium.
6 Apparatus
All volumetric glassware shall be class A and calibrated in accordance with ISO 648
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