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IS0
I NT ERN AT1 ON AL ORGAN IZATl O N FOR STAN DA Rb 1 ZATl ON
IS0 RECOMMENDATION
R 159
DETERMINATI(2hI OF TOTAL SULPHUR IN COAL
B~THE STRAMBI METHOD
1st EDITION
June 1960
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The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 159, Determination of Total Sulphur in Coal by the Strambi
Method, was drawn up by Technical Committee ISO/TC 27, Solid Mineral Fuels, the Secretariat
of which is held by the British Standards Institution (B.S.I.).
At its first meeting, held in London, in March 1950, Technical Committee ISOiTC 27
considered the Strambi (bomb calorimeter) method for the determination of total sulphur.
The general applicability of the method not then being established, the Committee, after deciding
upon various technical points, deferred further consideration of it.
By the time of the second meeting, held in London, in December 1951, evidence had
accumulated in support of the Strambi method, and it was agreed that Italy and the United
Kingdom should exchange samples and conduct further comparative tests on the Eschka and
the Strambi methods.
The first draft proposal was considered at the third meeting of the Technical Committee,
held in London, in November 1953. No general agreement could be reached, especially with
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regard to the extraction procedure and the behavior of coals containing barium. The Committee
called for further investigation of the method, and set up Working Group No. 3, Sulphur, to
conduct the necessary practical tests. The Committee also decided that a Draft IS0 Recom-
mendation should be developped, subject to the Working Group’s agreement on technical
points.
The Working Group met in May and in October 1954, and reached agreement on all the
major points at issue. A revised draft was circulated to the Working Group in June 1955,
and as a result of that consultation further changes were made.
A draft proposal for an IS0 Recommendation was circulated to the members of Technical
Committee ISO/TC 27, in September 1956 and was unanimously approved as a Draft IS0
Recommendation.
On 17 July 1957, the Draft IS0 Recommendation (No. 176) was distributed to all the IS0
Member Bodies and was approved, by the following 26 (out of a total of 39) Member Bodies:
Austria India Romania
Belgium * Ireland * Spain
v-
Burma Italy
Sweden
* Canada Mexico * Switzerland
Czechoslovakia Net herlands * Union of
Denmark * New Zealand South Africa
* Germany Pakistan
United Kingdom
* Greece Poland * U.S.A.
Hungary * Portugal * Yugoslavia
Two Member Bodies opposed the approval of the Draft: France, U.S.S.R.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in June 1960, to accept it as an IS0 RECOMMENDATION.
* These Member Bodies stated that they had no objection to the Draft being approved.
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ISO/R 159-1960 1 (E)
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IS0 Recommendation R 159 June 1960
DETERMINATION OF TOTAL SULPHUR IN COAL
BY THE STRAMBI METHOD
1. PRINCIPLE
The sample, intimately mixed with Eschka mixture, is burned in a calorimeter bomb made of
austenitic steel, filled with oxygen at a pressure of 25 atmospheres and containing ammonium
carbonate solution. Complete conversion to sulphate of the sulphur in the combustion pro-
ducts is ensured by the addition of hydrogen peroxide, and the sulphate is extracted with hot
water. The sulphate is determined either
gravimetrically as barium sulphate or
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titrimetrically using barium chromate.
2. RANGE
2.1 Gravimetric method. Up to 20 per cent of sulphur.
2.2 Titrimetric method. From 1.2 to 5 per cent of sulphur.
3. APPARATUS
All graduated apparatus should be of the best analytical quality obtainable and the balance
used should be sensitive to 0.1 mg.
3.1 For both methods
3.1.1 Calorimeter bomb, as used in the determination of the calorific value of coal. Sealing
washers of lead are not to be used.
3.1.2 Platinum crucible. The internal diameter of the base of the crucible should be not less
than 20 mm; the diameter of the top of the crucible should be not less than that of the
base.
3.1.3 Ignition wire, of platinum or nickel chromium alloy.
3.1.4 Cotton thread.
3.1.5 Glass rods, with flattened ends about 10 mm in diameter.
3.2 For gravimetric method
3.2.1 Electrically heated mufle furnace, with a substantially uniform hot zone at 800 f 25 OC,
and a flat plate, of silica (or other suitable insulating material), 6 mm thick, which fits
easily in the muffle, or
3.2.2 Air-oven, capable of being maintained at 130 f 10 OC, for drying Gooch filters.
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ISO/R 159- 1960 (E)
4. REAGENTS
All reagents are to be of analytical reagent quality and distilled water is to be used throughout.
4.1 For both methods
4.1.1 Eschka mixture. Mix two parts by weight of light, calcined magnesium oxide with one
part of anhydrous sodium or potassium carbonate. The mixture should entirely pass
a test sieve of 0.2 mm nominal aperture and its bulk density should be not greater than
0.50 g/ml. The bulk density may be conveniently determined as follows:
Place 50 g of the mixture in a 250 ml graduated cylinder; hold the cylinder in a vertical
position and tap it gently 100 times on a bench or table top; measure the volume occupied
by the mixture.
4.1.2 Ammonium carbonate solution, 10 per cent (weight/volume). Dissolve 10 g of ammonium
carbonate in 100 ml of water.
4.1.3 Hydrogen peroxide, 30 per cent (weight/volume) (“100 vol.”).
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Dissolve 80 g of sodium
4.1.4 Sodium hydroxide solution, 8 per cent (weight/volume).
hydroxide in 1 litre of water.
4.1.5 Hydrochloric acid, specific gravity d 1.18.
4.1.6 Standard sulphate solution. Dissolve 0.600 O g of potassium sulphate in water and dilute
to I O00 ml.
0.008 O g BaSO,
10 ml of standard sulphate solution I
1.033 ml of 0.1 N sodium thiosulphate solution.
4.2 For gravimetric method
4.2.1 Ammonia solution, specific gravity d 0.88 or nearest obtainable.
4.2.2 Barium chloride solution, 8.5 per cent (weight/volume). Dissolve 100 g of barium
chloride dihydrate in water and dilute to 1 litre. Filter before use through a fine-textured,
double acid-washed filter paper or filter paper pad.
4.2.3 Methyl red indicator solution. Dissolve 1 g of o-carboxybenzene-azo-dimethyl aniline
(methyl red) in 600 ml of ethanol or industrial methylated spirit and dilute to 1 litre
with water.
4.3 For titrimetric method
4.3.1 Potassium iodide.
4.3.2 Barium chromate solution, 3 per cent (weight/volume). To 30 g of barium chromate
add 100 ml of water and 100 ml of perchloric acid (specific gravity d 1.54) and warm
until solution is complete. Dilute the solution to 1 litre and filter into a storage bottle
through a fine-textured double acid-washed filter paper or filter paper pad. Store
overnight before using.
The solution prepared from commercially available barium chromate should be tested
for suitability. This is done by using it to carry out duplicate determinations, by the
method described under “Procedure” (see section 5) on accurately weighed portions
of between 0.13 and 0.14 g of potassium sulphate. If the mean of the results, expressed
as per cent of the amount of sulphur taken, is less than 99.5 or greater than 100.5, the
barium chromate in question should be rejected.
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ISO/R 159-1960 (E) I
A satisfactory solution may be prepared by the following method: Dissolve 28.92 g
of barium chloride dihydrate in 500 ml of water. Dissolve 23.00 g of potassium chromate
in 500 ml of water. Heat both solutions almost to boiling point and add the barium
chloride solution slowly to the potassium chromate solution, stirring during the addition.
Boil for 5 minutes, filter by suction through a fine-textured double acid-washed filter
paper supported in a Buchner funnel and wash with hot water until the last 20 ml of
the washings give no more than a faint trace of opalescence with silver nitrate solution.
Wash the precipitate by means of a jet of water into a 2 litre beaker, add 200 ml of
water and 100 ml of perchloric acid (specific gravity d 1.54) and warm until solution is
complete. Dilute the solution to 1 litre with water and filter into a storage bottle through
a fine-textured double acid-washed filter paper or filter paper pad.
4.3.3 Sodium acetate solution, 13.6 per cent (weight/volume). Dissolve either 136 g of anhy-
drous sodium acetate or 225 g of the trihydrate in water and dilute to 1 litre.
4.3.4 Ammonia solution. Dilute ammonia solution (specific gravity d 0.88 or nearest obtain-
able) with an equal volume of water. Store this solution over calcium oxide to remove
carbonate.
4.3.5 Sodium acetate solution, 0.9 per cent (weight/volume). Dissolve 9 g of anhydrous
sodium acetate or 15 g of the trihydrate in water and dilute to 1 litre.
4.3.6 Sodium thiosulphate solution, approximately 0.1 N. Dissolve 25 g of sodium thiosul-
phate pentahydrate in freshly boiled water, add 1 ml of chloroform and dilute to 1 O00 ml
with water. Standardize this solution before use with O. 1 N iodine or with O. 1 N potas-
sium iodate solution in the presence of a trace of potassium iodide.
4.3.1 Mixed indicator solution
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SOLUTION A. Dissolve O. 125 g of o-carboxybenzene-azo-dimethyl aniline (methyl red)
in 60 ml of ethanol or industrial methylated spirit and dilute to 100 ml with water.
SOLUTION B. Dissolve 0.083 g of 3 : 7 bis-dimethylamino-phenazothionium chloride
(methylene blue) in 100 ml
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