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IS0
I NTE RN AT I O N A L ORGAN I Z AT I ON FOR STA N DARD I Z AT I O N
IS0 RECOMMENDATION
R 332
DETERMINATION OF NITROGEN IN COAL
BY THE KJELDAHL METHOD
1st E D I TI ON
Au g u st 1 963
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For each individual country the oniy 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 332, Determination of Nitrogen in Coal by the Kjeldahl
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 1950 and led, in 1957, to the
adoption of a Draft IS0 Recommendation.
In April 1958, this Draft IS0 Recommendation (No. 222) was circulated to all the IS0
Member Bodies for enquiry. It was approved by the following Member Bodies:
Austria Greece Republic of South Africa
Belgium India Romania
Brazil Israel Spain
Burma Italy Turkey
Japan United Kingdom
Canada
Chile Mexico U.S.A.
Czechoslovakia Netherlands U.S.S.R.
Denmark New Zealand Yugoslavia
France Poland
Germany Portugal
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in August 1963, to accept it as an IS0 RECOMMENDATION.
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ISO/R 332 - 1963 (E)
I SO Reco m mend at i o n August 1963
R 332
DETERMINATION OF NITROGEN IN COAL
BY THE KJELDAHL METHOD
1. PRINCIPLE
Coal is heated with concentrated sulphuric acid in the presence of a mixed catalyst to convert the
nitrogen into ammonium sulphate, from which the ammonia, released by distillation from
alkaline solution, is absorbed in sulphuric acid, and the excess acid titrated with sodium or potas-
sium hydroxide.
2. APPARATUS
All volumetric apparatus should be of the best analytical quality obtainable, and the balance used
should be sensitive to 0.1 mg.
2.1 Digestion flask. A Kjeldahl flask of borosilicate glass having a pear-shaped bulb of 200 to
500 ml effective capacity and a neck about 20 cm long and 2.3 cm in internal diameter. A
suitable device for closing the mouth of the flask is provided, e.g. a light blown-glass stopper
which fits loosely in the neck of the flask.
2.2 Heating arrangement, to heat one or more flasks inclined at about 35" from the vertical.
3. REAGENTS
All reagents should be of analytical reagent quality, and distilled water should be used throughout.
3.1 Potassium sulphate, anhydrous.
3.2 Selenium powder, or
3.3 Mercuric sulphate, or
3.4 Mixed catalyst, containing by mass - 32 parts of potassium sulphate (3.1),
1 part of selenium powder (3.2), and
5 parts of mercuric sulphate (3.3).
Grind the above reagents in a mortar and mix them thoroughly.
3.5 Sucrose.
3.6 Sulphuric acid, relative density d 1.84.
3.7 Sodium hydroxide solution, 40 per cent (mass/volume). Dissolve 400 g of sodium hydrox-
ide in water and dilute to 1 litre.
3.8 Alkaline sodium sulphide solution. Dissolve 20 g of sodium sulphide (Na2S.gH20) in water,
dilute to 50 ml, add 600 ml of the sodium hydroxide solution (3.7) and mix well.
3.9 Sulphuric acid, approximately 0.1 N.
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ISO/R 332 - 1963 (E)
3.10 Sodium hydroxide solution, 0.1 N, or
3.11 Potassium hydroxide solution, 0.1 N.
3.12 Methyl red indicator solution. Dissolv
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