ISO 351:1996

SLOVENSKI STANDARD
SIST ISO 351:1998
01-februar-1998
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Solid mineral fuels -- Determination of total sulfur -- High temperature combustion
method
Combustibles minéraux solides -- Dosage du soufre total -- Méthode par combustion à
haute température
Ta slovenski standard je istoveten z: ISO 351:1996
ICS:
73.040 Premogi Coals
75.160.10 Trda goriva Solid fuels
SIST ISO 351:1998 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 351:1998

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SIST ISO 351:1998
INTERNATIONAL
ISO
STANDARD
351
Third edition
1996-02-15
Solid mineral fuels - Determination of
total Sulfur - High temperature
combustion method
Combustibles mineraux solides - Dosage du soufre total - Methode
par combustion 2 haute temperature
Reference number
ISO 351:1996(E)

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SIST ISO 351:1998
ISO 351:1996(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
(1 EC) 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 351 was prepared by Technical Committee
lSO/TC 27, Solid mineral fuels, Subcommittee SC 5, Methods of
analysis.
This third edition cancels and replaces the second edition
which has been technically revised.
(ISO 351 :1984)
1
0 ISO 1996
All rights reserved. Unless otherwise specified, 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 Permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1 211 Geneve 20 l Switzerland
Printed in Switzerland

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SIST ISO 351:1998
0 ISO
ISO 351:1996(E)
lntroduction
An alternative method to that specified in this International Standard is
given in ISO 334:1992, Solid mineral fuels - Determination o f total Sulfur
- Eschka method.
Ill

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SIST ISO 351:1998
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SIST ISO 351:1998
ISO 351:1996(E)
INTERNATIONAL STANDARD 0 ISO
- Determination of total Sulfur -
Solid mineral fuels
High temperature combustion method
ISO 2309:1980, Coke - Sampling.
1 Scope
ISO 5068: 1983, Brown coals and lignites - Determi-
This International Standard specifies a method of de-
nation of moisture content - Indirect gravimetric
termining the total Sulfur content of hard coal, brown
me thod.
coal and lignite, and coke by high temperature com-
bustion.
ISO 5069-2:1983, Brown coals and lignites - Prin-
ciples of sampling - Part 2: Sample preparation for
determina tion of moisture con ten t and for general
analysis.
2 Normative references
The following Standards contain provisions which,
3 Principle
through reference in this text, constitute provisions
of this International Standard. At the time of publi- A known mass of a Sample of coal or coke is burnt in
cation, the editions indicated were valid. All Standards
a stream of Oxygen, in a tube furnace at a tempera-
are subject to revision, and Parties to agreements
ture of 1 350 “C. The acid gases formed (chlorine and
based on this International Standard are encouraged oxides of Sulfur) are absorbed in hydrogen peroxide
to investigate the possibility of applying the most re- and subsequently determined titrimetrically. A cor-
cent editions of the Standards indicated below. rection is made to take account of any chlorine liber-
Members of IEC and ISO maintain registers of cur- ated and a suitable combustion additive prevents the
rently valid International Standards.
retention of Sulfur in the ash.
ISO 3313983, Coal - Determination of moisture in
4 Reactions
the analysis Sample - Direct gravimetric method.
ISO 587:1981, Solid mineral fuels - Determination
4.1 SO, + H,O, -+ H,SO,
of chlorine using Eschka mixture.
4.2 Cl, + H,O, --) 2HCI + 0,
Determination of mois ture in
ISO 687:1974, Coke -
the analysis Sample.
4.3 Na,B,O, + 2HCI + 5H,O -) 2NaCI + 4H,BO,
ISO 1015: 1992, Brown coals and lignites - Determi-
nation of moisture content - Direct volumetric
4.4 Na,B,O, + H,SO, + 5H,O + Na,SO, +
me thod.
4H,BO,
ISO 1170:1977, Coal and coke - Calculation of
4.5 NaCI + Hg(OH)CN -+ NaOH + HgCICN
analyses to different bases.
ISO 1988:1975, Hard coal - Sampling. 4.6 2NaOH + H,SO, --) Na,SO, + 2H,O
1

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SIST ISO 351:1998
0 ISO
ISO 351:1996(E)
5.6.3 Mixed solution
5 Reagents
Mix equal volumes of Solution A and Solution B. Store
WARNING - Care should be exercised when
in a dark bottle. Discard the mixed Solution after
handling reagents, many of which are toxic and
1 week.
corrosive.
5.7 Oxygen, laboratory grade, of purity at least
During the analysis, unless otherwise stated, use only
99,6 % (ndm).
reagents of recognized analytical grade and only dis-
tilled water or water of equivalent purity.
5.8 Sodium hydroxide on an inert base, preferably
of a coarse grading, for example 1,2 mm to 1,7 mm,
5.1 Aluminium Oxide (alumina), finely divided.
and preferably of the self-indicating type.
5.2 Hydrogen Peroxide, approximately 3 % (m/m)
6 Apparatus
neutral Solution.
6.1 Analytical balance, capable of weighing to the
Dilute 100 ml of 30 % (m/m) hydrogen peroxide sol-
nearest 0,l mg.
ution to 1 litre with water and neutralize with the
sodium tetraborate Solution (5.4) using the mixed in-
6.2 Graduated glassware, conforming to the re-
dicator (5.6).
quirements for class A in the International Standards
prepared by ISO/TC 48, Laboratory glassware and re-
5.3 Mercury(ll) oxycyanide, saturated Solution at
Ia ted appara tus.
20 “C, approximately 45 g/l.
6.3 Furnace, capable of heating a tube, of approxi-
Saturate a suitable volume of water with mercury(ll)
mately 28 mm external diameter over a length of
oxycyanide by prolonged agitation; filter and neutralize
125 mm to 150 mm, to a temperature of 1 350 “C.
the filtrate with the sulfuric acid (5.5) using
bromothymol blue as an external indicator. Store in a
The furnace may be heated electrically, using either
dark glass bottle; do not keep for more than 4 d.
Silicon carbide resistance rods (controlled by a variable
transformer) or a resistance wire (controlled by a
5.4 Sodium tetraborate, Standard volumetric sol-
variable resistance).
ution, c(Na,B,O,) = 0,025 mol/l.
6.4 Combustion tube, of approximately 28 mm ex-
Dissolve 9,534 2 g of sodium tetraborate decahydrate
ternal diameter, 3 mm wall thickness and 650 mm
in water and dilute to 1 Iitre. Mix thoroughly.
length, made of aluminous porcelain which is
impervious to gases up to the working temperature
5.5 Sulfuric acid, Standard volumetric Solution,
(see figure 1).
c(H*SO,) = 0,012 5 mol/l.
A straight tube is most convenient and may be used
in conjunction with an adapter of fused silica having
5.6 Mixed indicator solution.
a hell-shaped end, which gives a narrow clearance
from the inner wall of the heated tube, and a heat-
5.6.1 Solution A
resistant stopper (acrylonitrile or chloroprene is suit-
able). Alternatively, the tube may have, a beak end,
Dissolve 0,125 g of 2-(4-dimethylaminophenyl-
at the exit, with a tubulure to enable condensation
azo)benzoic acid, sodium salt (methyl red) in 100 ml
products to be washed out after a test; or a straight
of water.
tube of aluminous porcelain may be used in conjunc-
tion with a borosilicate glass adapter, having a cap-
5.6.2 Solution B
shaped end which fits onto the outer wall of the tube.
Dissolve 0,083 g of 3,7-bis(dimethylamino)pheno- In this case it will be necessary to lag the end of the
thiazine-5-ylium chloride (methylene blue) in 100 ml combustion tube with a suitable heat-resistant mineral
fibre to prevent condensation in the tube.
of water. Store in a dark bottle.

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SIST ISO 351:1998
ISO 351:1996(E)
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Figure 1 - Arrangement of furnace and absorption train
3

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SIST ISO 351:1998
ISO 351:1996(El) 0 ISO
6.5 Oxygen cylinder, fitted with a needle valve to through a pressure regulator adjusted to maintain
control the rate of flow of Oxygen (5.7), and a slight suction at the inlet end of the combustion tube.
flowmeter to measure up to 300 ml/min. The Oxygen
A convenient assembly of the apparatus is illustrated
should, as a precautionary measure, be passed
in figure 1.
through a U-tube packed with sodium hydroxide on
an in
...