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Ref. No.: IS0 / R 350 - 1963 (E)
IS0
I NT ERN AT1 ON AL O RG A N IZAT I O N FOR STA ND A R D I2 AT I ON
IS0 R ECOM MEN DATI ON
R 350
DETERMINATION OF CHLORINE IN COAL
BY THE BOMB-COMBUSTION METHOD
1st EDITION
December 1963
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized herefore 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 350, Determination of Chlorine in Coal by the Bomb-
Combustion 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.).
Work on this question by the Technical Committee began in 1953 and led, in 1957,
to the adoption of a Draft IS0 Recommendation.
In May 1958, this Draft IS0 Recommendation (No. 240) was circulated to all the IS0
Member Bodies for enquiry. It was approved subject to a few modifications of an editorial
nature, by the Following Member Bodies:
Austria India Portugal
Belgium Israel Republic
Burma Italy of South Africa
Japan Romania
Chile
Czechoslovakia Mexico Spain
Denmark Netherlands United Kingdom
Germany New Zealand U.S.S.R.
Yugoslavia
Greece Poland
One Member Body opposed the approval of the Draft: France.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in December 1963, to accept it as an IS0 RECOMMENDATION.
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P
IS0 / R 350 - 1963 (E)
IS0 Recommendation R 350 Decem ber 1963
DETERMINATION OF CHLORINE IN COAL
BY THE BOMB-COMBUSTION METHOD
1. PRINCIPLE
During combustion of the cilal in the calorimetric bomb in the determination of calorific value,
all the chlorine present is released and is found as chlorides in the bomb washings. It can, there-
fore, be readily determined titrimetrically (see note below).
If the determination is not associated with a determination of calorific value, precautions are
taken to minimize ejection of ash from the crucible, by mixing the coal with Eschka mixture,
and to promote rapid removal of all the acid gases from the vapour phase, by using ammonium
carbonate solution instead of water in the bomb.
NOTE. - The chlorine may also be determined potentiometrically.
2. APPARATUS
All graduated apparatus should be of the best analytical quality obtainable, and the balance
used should be sensitive to 0.1 mg.
2.1 Calorimetric bomb, which is not attacked by the acid gases produced, e.g. one of chromium-
nickel-molybdenum austenitic steel, with the usual fittings for ignition as in the determination
of calorific value, and of 300 f 50 ml capacity. A slow-release valve is unnecessary.
2.2 Crucible of platinum, nickel-chromium or silica, approximately 25 mm in diameter and
approximately 20 mm high.
2.3 Cylindrical metal vessel, such that the bomb will be fully immersed when approximately
two litres of water are added.
3. REAGENTS
All reagents should be of analytical reagent quality and distilled water should be used throughout.
3.1 Eschka mixture. Mix two parts by mass of light calcined magnesium oxide with one part
by mass of anhydrous sodium (or potassium) carbonate. The mixture should entirely pass
a test sieve of 0.2 mm aperture.
3.2 Nitric acid, chlorine-free, relative density d 1.42.
3.3 Ammonium carbonate solution, 10 per cent (weight/volume). Dissolve 10 g of ammonium
carbonate in 100 ml of water. The solution should be freshly prepared as required.
3.4 Volhard titration
3.4.1 Silver nitrate solution, 0.025 N. Heat crushed crystalline silver nitrate at 125 "C for
2 to 3 hours. Dissolve 4.247 g of the dried silver nitrate in water and dilute to 1000 ml.
Store in a bottle of amber glass.
3.4.2 Potassium thiocyanate solution. Dissolve approximately 3.5 g of potassium thiocyanate
in water and dilute to 1000 ml. Standardize by titration against the silver nitrate solution
(3.4.1) and adjust to exact equivalence.
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IS0 / R 350 - 1963 (E)
3.4.3 Nitrobenzene, light in colour.
3.4.4 Ferric alum (ammonium ferric sulphate) indicator solution. Add just sufficient of the
nitric acid (3.2) to a cold saturated solution of ferric alum to remove the brown colour.
3.5 Mohr titration
3.5.1 Silver nitrate solution, 0.050 N. Dissolve 8.494 g of dried silver nitrate, prepared as in
clause 3.4.1 in water, and dilute to 1000 ml.
3.5.2 Potassium chromate indicator solution. Dissolve 5 g of potassium chromate in 100 ml of
water.
4. PROCEDURE
4.1 After a determination of calorific value
At the end of the determination of calorific value, remove the bomb from the cylindrical
vessel, release the pressure, open the bomb and wash all the internal parts, including the
crucible, with 50 ml of hot distilled water, collecting the washings in a filtration beaker.
Add about 3 ml of the nitric acid (3.2), mix and filter, using a filter paper pad or a hardened
rapid-filtering paper, into a conical filtration beaker. Using a 10 ml portion of hot water
each time, wash the beaker and the filter four times.
Add 20.0 ml of the silver nitrate solution (3.4.1), mix and leave to stand
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