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INTERNATIONAL
STANDARD 334
Second edition
1992-12-15
- Determination of
Solid mineral fuels
total Sulfur - Eschka method
Combustibles min&aux solides - Dosage du soufre total - M&hode
Eschka
Reference number
ISO 334: 1992(E)
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ISO 334:1992(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national Standards bodies (ISO member bodies). The work
of preparing International Standards is normally carried out through ISO
technical committees. Esch member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 334 was prepared by Technical Committee
ISOFC 27, Solid mineral fuels, Sub-Committee SC 5, Methods of
analysis.
This second edition cancels and replaces the first edition (ISO 334:1975),
of which it constitutes a technical revision.
Annex A of this International Standard is for information only.
0 ISO 1992
All rights reserved. No part of this publication may be reproduced or utilized in any form or
by any means, electronie or mechanical, including photocopying and microfilm, without per-
mission in writing from the publisher.
International Organization for Standardiza tion
Case Postale 56 l CH-l 21 1 Geneve 20 l Switzerland
Printed in Switzerland
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ISO 334:1992(E)
Introduction
An alternative reference method to that specified in this International
Standard is given in ISO 351:1984, Solid mineral fuels - Determination
of total Sulfur - High tempera ture combus tion me thod.
Instrumental methods for a more rapid determination of total Sulfur are
now available. If such a method is to be used, it is important to demon-
strate that the method is free from bias, when compared to this reference
method, and will give levels of repeatability and reproducibility which are
the same as, or better than, those quoted for the reference method (see
clause 9).
. . .
Ill
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ISO 334:1992(E)
INTERNATIONAL STANDARD
Solid mineral fuels - Determination of total Sulfur -
Eschka method
determina tion of moisture con ten t and for general
1 Scope
analysis.
This International Standard specifies a reference
method for determining the total Sulfur content of
3 Principle
hard coal, brown coals and lignites, and coke by the
Eschka method.
A test Portion is ignited in intimate contact with
Eschka mixture in an oxidizing atmosphere, to remove
combustible matter and to convert the Sulfur to sul-
fate. This is then extracted with hydrochloric acid sol-
2 Normative references
ution and determined gravimetrically by precipitation
with barium chloride.
The following Standards contain provisions which,
through reference in this text, constitute provisions
4 Reagents
of this International Standard. At the time of publica-
tion, the editions indicated were valid. All Standards
WARNING - Care should be exercised when
are subject to revision, and Parties to agreements
handling the reagents, many of which are toxic
based on this International Standard are encouraged
and corrosive.
to investigate the possibility of applying the most re-
cent editions of the Standards indicated below.
During the analysis, unless otherwise stated, use only
Members of IEC and ISO maintain registers of cur-
reagents of recognized analytical grade and only dis-
rently valid International Standards.
tilled water or water of equivalent purity.
ISO 331:1983, Coal - Determination of mois ture in
4.1 Eschka mixture.
the analysis Sample - Direct gravimetric method.
Mix two Parts by mass of light, calcined magnesium
ISO 687:1974, Coke - Determination of mois ture in
Oxide with one part by mass of anhydrous sodium (or
the analysis Sample.
potassium) carbonate. The mixture shall entirely pass
a test sieve of 212 Fm nominal size of openings.
ISO 1015:1992, Brown coals and lignites - Determi-
nation of moisture content - Direct volumetric
4.2 Hydrochlorit acid, concentrated, p approxi-
method.
mately 1 ,18 g/ml, approximately 36 % (m/m).
ISO 1170: 1977, Coal and coke -- Calculation of ana-
lyses to different bases.
4.3 Potassium sulfate, Solution.
Weigh, to the nearest 0,l mg, about 2 g of potassium
ISO 1988: 1975, Hard coal - Sampling.
sulfate, previously dried at a temperature of 105 “C to
110 “C. Dissolve in water and dilute to 1 litre.
ISO 2309:1980, Coke - Sampling.
ISO 5068: 1983, Brown coals and lignites - Determi-
4.4 Barium chloride, approximately 85 g/l Solution.
na tion of moisture con tent - Indirect gravimetric
Dissolve 100 g of barium chloride dihydrate in water
method.
and dilute to 1 litre. Filter before use through a close-
textured, doubly acid-washed filter-paper or filter-
ISO 5069-2: 1983, Brown coals and lignites - Prin-
Paper pad.
ciples of sampling - Part 2: Sample preparation for
1
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ISO 334:1992(E)
4.5 Methyl red, indicator solution.
7 Procedure
Dissolve 1 g of 2-(4-dimethylaminophenylazo)benzoic
acid, sodium salt (methyl red) in 1 litre of water.
7.1 Test psrtisn
4.6 Ammonia, concentrated Solution, not less than
7.4.1 For coal
25 % (dm).
Take a test Portion of the mass given in table 1 (for
4.7 Silver nitrate, 17 g/l solution.
the expected total Sulfur content), weighing to the
nearest 0,l mg.
Dissolve 17 g of silver nitrate in water and dilute to 1
Iitre. Store in a dark glass bottle.
Table ll - Test Portion for coal
5 Apparatus
Expected total Sulfur
Mass of test Portion
5.1 Analytical balance, capable of weighing to the
nearest 0,l mg.
5.2 Graduated glassware, conforming to the re-
quirements for class A in the International Standards
prepared by lSO/TC 48.
5.3 Electrically heated muffle furnace, capable of
being maintained at a temperature of
7.1.2 For coke
800 “C + 25 OC. The Ventilation through the muffle
furnaceihall be such as to give about five air changes
Take a test Portion of 1 g, weighing to the nearest
per minute.
0,l mg.
5.4 Crucible, of platinum, silica or glazed porcelain,
of capacity approximately 25 ml. 7.2 Charging the crucible
Cover the bottom of the crucible (5.4) uniformly with
Flat plate, 6 mm thick, of silica ior other suitable
5.5
0,5 g of the Eschka mixture (4.1), weighed to the
refractory material), which fits easily into the muffle
nearest 0,l mg. Mix the test portion intimately with
furnace (5.3).
2,5 g of the Eschka mixture, weighed to the nearest
0,l mg, in a suitable vessel. Transfer the mixture to
5.6 Gooch crucible, of glazed porcelain or sintered
the 25 ml crucible. Level the contents by tapping the
glass.
crucible gently on the bench and cover the contents
uniformly with 1,0 g of the Eschka mixture, weighed
Air oven, capable of being maintained at a tem-
5.7
to the nearest 0,l mg.
perature of 130 “C + 10 “C.
-
NOTE 1 The entire 4 g of the Eschka mixture should be
weighed out and the 0,5 g and 1 g portions, required for the
6 Preparation of test Sample
bottom and top layers, should be extracted from this. For
this purpose, it is convenient to calibrate a small glass tube
The test Sample is the general analysis test Sample
for each bath of Eschka mixture, to deliver 0,5 g and 1 g
prepared in accordance with ISO 1988, ISO 2309 or
without weighing. The bottom layer of Eschka mixture be-
ISO 5069-2, as appropriate. Expose the Sample, in a
low the test Portion mixture reduces attack on the porcelain
thin layer, for the minimum time required for the
surface, so that the extraction of sulfate with hot water is
moisture content to resch approximate equilibrium
complete even when the surface deteriorates.
with the laboratory atmosphere (this is particularly
important for brown coals and lignites).
7.3 Ignition
Before commencing the determination, thoroughly
mix the test Sample for at least 1 min, preferably by
7.3.1 For coal
mechanical means.
If the results are to be calculated other than on an Place the charged crucible (and any others up to the
limit of the muffle furnace capacity) in the cold muffle
“air-dried” basis (see clause 8), then, after weighing
furnace (5.3) and raise the temperature to
the test Portion (see 7.1), determine the moi
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