ISO 19950:2015

INTERNATIONAL ISO
STANDARD 19950
First edition
2015-12-01
Aluminium oxide primarily used
for the production of aluminium —
Determination of alpha alumina
content — Method using X-ray
diffraction net peak areas
Oxyde d’aluminium principalement utilisé pour la production
d’aluminium — Dosage de la teneur en alumine alpha — Méthode
utilisant la diffraction à rayons X des surfaces de pic net
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 1
5 Apparatus . 2
6 Procedure. 2
7 Calculation and expression of results . 4
8 Precision . 5
9 Test report . 6
Annex A (informative) Results of interlaboratory test program . 7
Bibliography . 8
Foreword
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aluminium.
iv © ISO 2015 – All rights reserved

Introduction
This International Standard is based on an Australian Standard AS 2879.3-2010, Alumina —
Determination of alpha alumina content by X-ray diffraction.
INTERNATIONAL STANDARD ISO 19950:2015(E)
Aluminium oxide primarily used for the production of
aluminium — Determination of alpha alumina content —
Method using X-ray diffraction net peak areas
1 Scope
This International Standard sets out an X-ray diffraction method for the determination of the alpha
alumina content of smelter grade alumina. The method is applicable to smelter grade alumina
containing alpha phase at levels up to 50 %. The percentage by mass of alpha alumina is determined on
an “as received” basis.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
AS 4538.2, Guide to the sampling of alumina — Preparation of samples
3 Principle
The integrated peak areas of the (012) and (116) lattice plane reflections (nominal d spacings 0,348 nm
and 0,160 nm) are measured for the test sample and a 100 % alpha alumina calibration standard. The
ratio between the net peak area intensities for the test sample and for the standard is determined and
the alpha alumina content calculated from this ratio.
4 Reagents
4.1 General
During the analysis, only reagents of recognized analytical reagent grade and only distilled water, or
water of equivalent purity, shall be used.
4.2 100 % alpha alumina calibration standard, prepared in accordance with either 4.2.1 or 4.2.2.
4.2.1 A commercially available, certified 100 % alpha alumina calibration standard suitable for
diffraction analysis.
4.2.2 An in-house produced 100 % alumina calibration standard prepared in accordance with 6.1 and
using the following reagents.
4.2.2.1 Hydrochloric acid (100 g/l).
4.2.2.2 Smelter grade alumina.
NOTE The type of alumina used as the base for the 100 % alpha alumina calibration standard can affect the
peak areas measured. Grades of the base alumina other than smelter grade can yield different peak area intensities.
5 Apparatus
5.1 X-ray diffractometer.
5.2 Hydraulic press, suitable for preparing mounts.
5.3 Rotary divider or riffle.
5.4 Grinding mill, capable of grinding alumina to a particle size 0f 90 % less than 45 µm.
5.5 In-house alpha aluminium apparatus, prepared as follows (see 5.5.1 to 5.5.5). Necessary only if
alpha aluminium standard (4.2.2) is to be prepared in accordance with 6.1.
5.5.1 Platinum dish and lid.
5.5.2 Coarse filter paper.
5.5.3 Drying oven, capable of being controlled at (105 ± 5) °C.
5.5.4 Magnetic stirrer.
5.5.5 Electric furnace, capable of being controlled at (1 300 ± 50) °C. Necessary only if the 100 %
alpha alumina calibration standard (4.2.2) is to be prepared in-house in accordance with 6.1.
6 Procedure
6.1 Preparation of 100 % alpha alumina calibration standard
The calibration standard shall be prepared as follows.
a) Weigh out approximately 100 g of smelter grade alumina (4.2.2.2).
b) Transfer to a 600 ml beaker and add 250 ml of hydrochloric acid (4.2.2.1). Stir the solution at
ambient temperature for 3 h using the magnetic stirrer (5.5.4).
c) Filter the alumina slurry through a coarse filter paper (5.5.2). Wash the paper and the residue
thoroughly three or four times with water to remove entrained hydrochloric acid.
NOTE 1 This washing procedure reduces the soda and other impurities in the alumina. Soda will react to
form a beta alumina phase on calcining which will reduce the alpha phase content.
d) Dry the alumina residue in the drying oven (5.5.3) at (105 ± 5) °C for 2 h. Transfer the dried alumina
residue to a platinum dish (5.5.1). Cover the dish with the platinum lid.
e) Transfer the dish into the electric furnace (5.5.5) at 300 °C. Raise the furnace temperature over a
period of
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