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UDC 662.61.7 : 620.1
IS0
FOR S TA N DARD I ZAT I O N
INTERN AT I ON AL O R G A N I2 AT I ON
IS0 RECOMMENDATION
DETERMINATION OF ARSENIC
IN COAL AND COKE
1 st EDITION
July 1967
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 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 601, Determination of Arsenic in Coal and Coke, was drawn
up by Technical Committee ISO/TC 27, Solid Mineral Fuels, the Secretariat of which is held by
the British Standards Institution (BSI).
Work on this question by the Technical Committee began in 1951 and led, in 1963, to the
adoption of a Draft IS0 Recommendation.
In March 1964, this Draft IS0 Recommendation (No.678) 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:
Switzerland
Australia Germany
Austria Turkey
Italy
Belgium Japan U.A.R.
Brazil Korea, Rep. of United Kingdom
Canada Netherlands U.S.A.
Chile New Zealand U.S.S.R.
Colombia Poland
Czechoslovakia Republic
Denmark of South Africa
France Romania
One Member Body opposed the approval of the Draft:
India
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, wich decided, in July 1967, to accept it as an IS0 RECOMMENDATION.
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ISOlR 601 - 1967 (E)
IS0 Recommendation R 601 July 1967
DETERMINATION OF ARSENIC IN COAL AND COKE
1. SCOPE
This IS0 Recommendation describes a photometric method of determining the amount of arsenic
in hard coal, brown coal and lignite, and coke.
The method is applicable to samples containing not more than 0.0016 % of arsenic (or 0.0021 %
of arsenious oxide). For samples containing more arsenic, the procedure requires modification
(see Note 1).
2. PRINCIPLE
The sample is oxidized by means of nitric and sulphuric acids or by the use of Eschka mixture.
The arsenic is reduced to the trivalent state and evolved as arsine by the action of zinc in sulphuric
acid or hydrochloric acid medium. The arsine evolved is absorbed and oxidized to arsenic acid
by a dilute iodine solution. Treatment with ammonium molybdate solution and reduction with
hydrazine sulphate produces a molybdenum-blue coloration. The optical density of the coloured
solution is proportional to the arsenic present in the sample".
3. REAGENTS
All reagents should be of arsenic-free analytical reagent quality, except in the case of arsenious
oxide, which should be of the highest purity obtainable. Distilled water should be used throughout.
3.1 Zinc, granulated, containing less than 0.000002 % of arsenic.
3.2 Sulphuric acid, d 1.84.
3.3 Nitric acid, d 1.42.
3.4 Hydrochloric acid, d 1.18.
3.5 Hydrazine sulphate solution, 0.15 % (m/v). Dissolve 0.15 g of hydrazine sulphate in 100 ml
of water.
3.6 Stannous chloride solution, 33.5 % (m/v). Dissolve 40 g of stannous chloride, SnC12. 2H20,
in hydrochloric acid (d 1.18) and dilute to 100 ml with the hydrochloric acid.
3.7 Potassium iodide solution, 15 % (m/v). Dissolve 15 g of potassium iodide in 100 ml of water.
Prepare fresh before using.
3.8 Lead acetate solution, saturated. Prepare fresh before using.
3.9 Sulphuric acid solution, approximately 7 N. Add 200 ml of the sulphuric acid (3.2) cautiously
to about 700 ml of water, cool and dilute to 1 litre.
3.10 Ammonium molybdate solution, 1 % (m/v) in 5 N sulphuric acid. Dissolve 5 g of ammonium
molybdate (NH4)~Mo7024.4H20, in about 400 ml of sulphuric acid (3.14) and dilute to
500 ml with the sulphuric acid (3.14).
3.11 Stock iodine solution, approximately 0.02 N. Dissolve 2.54 g of iodine in 25 ml of water
containing 8 g of potassium iodine. Dilute to 1000 ml and store in a dark glass bottle.
The determination of arsenic in microgram quantities in coal and coke,
See
A. Crawford, J.G. Palmer, J. H. Wood, 1958/2,227-294, Mikrochim. Acta.
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ISOlR 601 - 1967 (E)
3.12 Working iodine solution, approximately 0.002 N. Dilute 10 ml of the stock iodine solution
(3.11) to 100 ml. Prepare fresh before using.
3.13 Working iodine solution, approximately 0.001 N. Dilute 5 ml of the stock iodine solution
(3.11) to 100 ml. Prepare fresh before using.
3.14 Sulphuric acid solution, 5.0 N. Add 140 ml of the sulphuric acid (3.2) cautiously to about
500 ml of water, cool and dilute to 1000 ml. Standardize against sodium carbonate, using
methyl orange as indicator and adjust to 5.0 N.
3.15 Standard arsenic solution (1 ml = 1 mg As). Weigh 0.1320 g of arsenious oxide, previously
dried at 110 "C for 2 hours, and dissolve in 50 ml of water containing 0.5 ml of 70 % (m/v)
sodium hydroxide solution. Add 2 ml of the sulphuric acid (3.14) and dilute to 100 ml.
3.16 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.
4. APPARATUS
All glass apparatus should be constructed from borosilicate glass and should be of the best
analytical quality obtainable. Ground glass joints, when used, should comply with the relevant
IS0 Recommendation*. The balance used should be accurate to 0.1 mg.
4.1 Wet oxidation apparatus
A suitable apparatus is illustrated in Figure 1, page 7. It consists of the following parts:
4.1.1 KjeldahlJEasks, of 300 ml capacity fitted with a ground glass socket of joint size 24/29.
4.1.2 Fume ducts, each fitted with a dropping funnel and, at one end, a ground glass cone of
joint size 24/29. The ducts may be of one-piece construction or assembled from separate
of ground glass joints.
units by means
4.1.3 Fume extractor, consisting of a glass tube, of diameter approximately 38 mm, sealed at
one end and drawn out at the other to form a connection point for the pump. The tube
J
is fitted with a series of lipped holes, to accommodate several fume ducts, and with a
drain cock.
4.1.4 Glass water pump
4.1.5 Digestion rack, fitted with several positions, each of which will accommodate a Kjeldahl
flask held at an angle of 45", with a holder for the fume extractor.
4.2 Dry oxidation apparatus
4.2.1 Electrically heated muffle furnace, with a zone of substantially uniform temperature at
800 & 25 "C and a ventilation rate of about 5 air changes per minute.
4.2.2 Crucibles of porcelain or silica, of approximately 25 ml capacity.
4.2.3 Fiat plate 6 mm thick, of silica or other suitable insulating material which fits easily in
the muffle.
* IS0 Recommendation R 383, Interchangeable Conical Ground Glass Joints, which provides for a sue designation for each
of the standard joints based on the large-end diameter and nominal length in millimetres.
I
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ISO/R 601 - 1967 (E)
4.3 Evolution apparatus
This apparatus has been designed to ensure the efficient generation and absorption of arsine ;
the dimensions given should be adhered to. It consists of the following parts (see Figure 2,
page 8):
4.3.1 Evolution$usk (A), a 50 ml conical flask fitted with a ground glass socket of joint size
19/26.
4.3.2 Delivery tube (B), consisting of thick-walled glass tubing of internal diameter 4 mm,
fitted at one end with a ground glass cone of joint size 19/26 and at the other end with a
ground glass cone of joint size 7/16. Glass hooks are fitted just above the smaller cone.
4.3.3 Extension delivery tube (C), consisting of thick-walled glass tubing of internal diameter
4 mm fitted at one end with a ground glass socket of joint size 7/16, with glass hooks
beneath, and drawn out at the other end to a portion 80 mm long of internal diameter
2 mm.
4.3.4 Absorption tube (D), of length approximately 150 mm and fitted at one end with a ground
glass stopper of joint size 14/15. The internal diameter of the tube is 15 mm at the stopper
end, but at the other end a portion about 80 mm long has an internal diameter of 11 mm.
4.3.5 Helix (E), of glass rod or inert plastics material such as unplasticized polyvinyl chloride,
of circular section and of length 80 mm and 5 mm pitch. The helix has an outside dia-
meter such that it fits the lower half of the absorption tube freely but not loosely and an
internal diameter slightly larger than the external diameter of the narrow end of delivery
tube C. A correctly fitted helix causes gas bubbles to follow a spiral course freely and
without by-pass.
4.3.6 Springs. Small springs of suitable metal to ensure a gas-tight joint between the delivery
tube B and its extension C.
4.4 Spectrophotometer, of a suitable type, with accessories.
4.5 5 ml pipette and three 5 ml burettes graduated to 0.01 ml.
n
FIG. 1. - Wet oxidation apparatus
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ISO/R 601 - 1967 (E)
Dimensions in millimetres
.;
Li C
--
V
5
Y
c
ET
19/26
4
I
E
lnt. 1 @
N
Y
J
I
2 Int. 57
c
I
FIG. 2. - Evolution apparatus
Joint size designations in accordance with I
...