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Ref. No. : ISO/R 779-1968 (E)
IS0
I N T ERN AT1 O N A L O RG A N IZATl ON FO R STA N DA R D IZATl ON
IS0 RECOMMENDATION
R 779
PU LPS
DETERMINATION OF IRON
1 st EDIT I ON
July 1968
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 779, Pulp - Determination of iron, was drawn up by Technical
Committee ISO/TC 6, Paper, board and pulps, the Secretariat of which is held by the Association
Française de Normalisation (AFNOR).
Work on this question by the Technical Committee began in 1965 and led, the same year, to the
adoption of a Draft IS0 Recommendation.
In November 1966, this Draft IS0 Recommendation (No. 1070) 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 :
Argentina India Romania
Australia Iran Spain
Belgium Israel Sweden
Switzerland
Brazil Italy
Bulgaria Japan Turkey
Canada Korea, Rep. of U.A.R.
Czechoslovakia Mexico United Kingdom
Denmark Netherlands U.S.A.
Finland New Zealand U.S.S.R.
Yugoslavia
France Norway
Germany Portugal
One Member Body opposed the approval of the Draft :
Cuba
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in July 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 779-1968 (E)
IS0 Recommendation July 1968
R 779
PU LPS
DETERMINATION OF IRON
1. SCOPE
The IS0 Recommendation describes a method for the determination of the iron content of pulp.
2. FIELD OF APPLICATION
This method applies to all kinds of pulp.
3. PRINCIPLE OF THE METHOD
The pulp is ashed and the ash is dissolved in hydrochloric acid. The concentration of iron is
determined colorimetrically with ortho-phenanthroline by measuring the optical density at 5 10 nm.
4. REAGENTS
All reagents should be of analytical grade.
4.1 Hydrochloric acid, about 6 M. Dilute 500 mi of hydrochloric acid (d = 1.19) with 500 ml of
distilled water.
4.2 Sodium acetate solution, 4 M. Dissolve 540 g of sodium acetate (Na COOCH3 . 3 H2O) in
distilled water and dilute to 1 litre.
4.3 Hydroxylamine hydrochloride solution. Dissolve 2 g of hydroxylamine hydrochloride
(",OH . HCI) in 100 ml of distilled water.
4.4 Ortho-phenanthroline hydrochloride solution. Dissolve 1 g of ortho-phenanthroline hydro-
chloride (C,2H8N2 . HCI . H20) in 100 ml of distilled water. Keep the solution in the dark.
Use only a colourless solution.
4.5
Standard iron solution, 0.1 mg of iron per millilitre. Dissolve 0.100 g of pure iron wire in the
smallest possible quantity of hydrochloric acid (d = 1.19) in a 1 litre volumetric flask and
dilute to the mark with distilled water.
5. APPARATUS
5. I Dishes of platinum, of porcelain or of quartz,
5.2 Spectrophotometer or filter colorimeter.
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ISO/R 779-1968 (E)
1
6. CALIBRATION
Dilute the standard iron solution (4.5) ten times so that 1 ml corresponds to 0.01 mg of Fe. Pipette
aliquots of 5.0, 10.0, 15.0 and 20.0 mi of the diluted solution into 50 ml volumetric flasks. Use a
fifth flask for the preparation pf a reference solution. Add to each flask 1 nil of hydroxylamine hydro-
chloride solution (4.3) and 1 mi of orthophenanthroline hydrochloride soliitim (4.4) and dilute to the
mark with distilled water. After 15 minutes measure the optical density at 510 nm with the iron free
solution as a reference.
NOTE. - Avoid expoïure of thc c<,lourcd solution to direct sunlight.
The iron concentrations of the coloured solutions are 1 .O, 2.0, 3.0 and 4.0 mg of Fe per litre respect-
ively. Plot on a diagram the optical density values
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