SIST ISO 333:1998

SLOVENSKI STANDARD
SIST ISO 333:1998
01-februar-1998
3UHPRJ'RORþHYDQMHGXãLND3ROPLNUR.MHOGDKORYDPHWRGD
Coal -- Determination of nitrogen -- Semi-micro Kjeldahl method
Charbon -- Dosage de l'azote -- Méthode semi-micrométrique de Kjeldahl
Ta slovenski standard je istoveten z: ISO 333:1996
ICS:
73.040 Premogi Coals
SIST ISO 333:1998 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 333:1998

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SIST ISO 333:1998
INTERNATIONAL
STANDARD
Fourth edition
1996-03-I 5
- Determination of nitrogen -
Coal
Semi-micro Kjeldahl method
Charbon - Dosage de I ’azote - M6 thode semi-microm6 trique de
Kjeldahl
Reference number
IS0 333:1996(E)

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SIST ISO 333:1998
IS0 333:1996(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
technical committees. Each 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. IS0
collaborates closely with the International Electrotechnical Commission
(I 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 IS0 333 was prepared by Technical Committee
lSO/TC 27, Solid mineral fuels, Subcommittee SC 5, Methods of
analysis.
This fourth edition cancels and replaces the third edition (IS0 333:1983),
which has been technically revised.
Annex A of this International Standard is for information only.
0 IS0 1996
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii

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SIST ISO 333:1998
INTERNATIONAL STANDARD 0 IS0 IS0 333:1996(E)
- Determination of nitrogen
Coal - Semi-micro
Kjeldahl method
1 Scope 3 Principle
A known mass of the sample is heated with concen-
This International Standard specifies a method of de-
termining the nitrogen content of hard coal, brown trated sulfuric acid in the presence of a mixed catalyst
coal and lignite by the semi-micro Kjeldahl method. to convert the nitrogen into ammonium sulfate, from
which the ammonia, released by steam distillation
from alkaline solution, is absorbed in boric acid and
determined by titration with sulfuric acid.
2 Normative references
4 Reagents
The following standards contain provisions which,
WARNING - Care should be exercised when
through reference in this text, constitute provisions
handling reagents, many of which are toxic and
of this International Standard. At the time of publi-
corrosive.
cation, the editions indicated were valid. All standards
are subject to revision, and parties to agreements
During the analysis, unless otherwise stated, use only
based on this International Standard are encouraged
reagents of recognized analytical grade and only dis-
to investigate the possibility of applying the most re-
tilled water, or water of equivalent purity.
cent editions of the standards indicated below.
Members of IEC and IS0 maintain registers of cur-
rently valid International Standards.
4.1 Mixed catalyst, containing by mass:
IS0 331:1983, Coal - Determination of moisture in
90 parts of anhydrous potassium sulfate;
the analysis sample - Direct gravimetric method.
2 parts of selenium powder;
IS0 1015:1992, Brown coals and /ignites - Determi-
nation of moisture content - Direct volumetric 5 parts of vanadium pentoxide.
method.
Grind the above reagents in a mortar and mix them
thoroughly.
IS0 1170:1977, Coal and coke - Calculation of
analyses to different bases.
4.2 Sucrose.
IS0 1988:1975, Hard coal - Sampling.
4.3 Sulfuric acid, concentrated, approximately
IS0 5068: 1983, Brown coals and /ignites - Determi-
98 % (m/m).
nation of moisture content - Indirect gravimetric
method.
4.4 Boric acid solution, saturated.
IS0 5069-2: 1983, Brown coals and /ignites - Princi-
Part 2: Sample preparation for Dissolve 60 g of boric acid in 1 litre of hot water, cool
ples of sampling -
and allow to stand for 3 d before decanting the clear
determination of moisture content and for general
solution.
analysis.

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SIST ISO 333:1998
0 IS0
IS0 333:1996(E)
5.5 Receiver, a wide-necked, flat-bottomed conical
4.5 Sodium hydroxide, 400 g/l solution.
flask, of capacity 100 ml.
Dissolve 400 g of sodium hyd roxide in water, dilute
to 1 litre and mix thoroughly.
5.6 Heating apparatus, capable of heating one or
more digestion flasks while supporting it at an angle
NOTE 1 It is advisable to stir the mixture frequently while
of 35” from the vertical. An electric heating unit or a
dissolving in order to dissipate the heat of solution.
gas microburner may be used. An example of a suit-
able electric heating unit, capable of heating several
4.6 Sulfuric acid, standard volumetric solution,
flasks simultaneously, is shown in figure2.
= 0,005 mol/l.
c(H*so4>
6 Preparation of the test sample
4.7 Mixed indicator solution.
Prepare the test sample for general analysis in ac-
4.7.1 Solution A.
cordance with IS0 1988, or IS0 5069-2, as appropri-
Dissolve 0,125 g of 2-(4-dimethylaminophenylazo) ate. Ensure that the moisture content of the sample
benzoic acid, sodium salt (methyl red) in 60 ml of is in equilibrium with the laboratory atmosphere, ex-
ethanol and dilute to 100 ml with water. posing it, if necessary, in a thin layer for the minimum
time required to achieve equilibrium.
4.7.2 Solution B .
Before commencing the determination, thoroughly
Dissolve 0,083 g of 3,7-bis(dimethylamino)pheno- mix the test sample for at least 1 min, preferably by
thiazin-5-ylium chloride (methylene blue) in 100 ml of mechanical means.
water. Store in a dark bottle.
If the results are to be calculated other than on an
“air-dried” basis (see clause 91, after weighing the
4.7.3 Mixed solution.
test portion, determine the moisture content using a
Mix equal volumes of solution A and solution B. Store further portion of the test sample by the method de-
in a dark bottle. Discard the mixed solution after scribed in IS0 331, IS0 1015 or IS0 5068, as appro-
1 week. priate.
5 Apparatus
7 Procedure
5.1 Analytical balance, capable of weighing to the
7.1 Digestion
nearest 0,l mg.
Weigh, to the nearest 0,l mg, about 0,l g of the test
5.2 Graduated glassware, conforming to the re-
sample and transfer it quantitatively to the digestion
quirements for Grade “A” in the International Stan-
flask (5.3). Add 2 g of the mixed catalyst (4.1) and
dards prepared by ISOnC 48, Laboratory glassware
shake to mix. Add 4 ml of the sulfuric acid (4.3) and
and r-elated apparatus.
mix again.
Switch on the electric heating unit (5.6) at approxi-
5.3 Digestion flask, of borosili
...