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Ref. No. : ISO/R 682-1968 (E)
IS0
I NT ERN AT1 ON A L O RG A N IZATl O N FOR STAN DA RD l ZATl ON
IS0 RECOMMENDATION
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R 682
CHEMICAL ANALYSIS OF CEMENTS
DETERMINATION OF SULPHUR AS SULPHIDE
1st EDITION
March 1968
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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 682, Chemical analysis of cements - Determination of sulphur as
sulphide, was drawn up by Technical Committee ISO/TC 74, Hydraulic binders, the Secretariat of
which is held by the Institut Belge de Normalisation (IBN).
Work on this question by the Technical Committee began in 1958 and led, in 1963, to the
adoption of a Draft IS0 Recommendation.
In February 1965, this Draft IS0 Recommendation (No. 775) was circulated to all the IS0
1
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature,
by the following Member Bodies :
Argentina Ireland Romania
Sweden
Australia Israel
Turkey
Austria Italy
Belgium Japan U.A.R.
Czechoslovakia Korea, Rep. of United Kingdom
Denmark Netherlands U.S.A.
France New Zealand U.S.S.R.
Germany Norway Yugoslavia
Hungary Poland
India 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 March 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 682-1968 (E
IS0 Recommendation R 682 ,March 1968
CHEMICAL ANALYSIS OF CEMENTS
DETERMINATION OF SULPHUR AS SULPHIDE
1. SCOPE
This IS0 Recommendation describes the method for determination of sulphur present in cements as
sulphide.
2. PRiNCIPLE OF METHOD
The sulphides contained in the sample are attacked by a strong acid in a reducing medium. Hydrogen
sulphide formed is entrained by an air flow in an ammoniacal solution of zinc or cadmium. Zincor.
cadmium sulphide precipitated is determined by iodimetry.
3. REAGENTS
3.1 Starch solution
To 100 ml of boiling water add 5 rnl of a suspension containing 20 g of starch in 100 ml of cold
water. Cool. Add 10 ml of a solution containing 10 g of sodium carbonate per 100 ml and add
3 g of potassium iodide.
3.2 Standard potassium permanganate solution (0.03 N)
Prepare a solution containing 0.94 g of potassium permanganate per litre, taking the usual pre-
cautions. Standardize against analytical quality sodium oxalate (about 0.1 50 g weighed accu-
rately). Let this mass be A requiring a volume B of potassium permanganate solution.
Sodium thiosulphate solution (0.03 N)
3.3
Prepare a solution containing 7.4 g of Na, S,O, .5 H,O per litre.
Standardize it as follows :
Dissolve 1 g of potassium iodide in 300 ml of cold water in a 500 ml conical flask and add
10 mi of hydrochloric acid. Run in 25 ml of the standard potassium permanganate solution
(3.2) from a burette.
Shake gently, stopper the flask and allow to stand for 5 min. Titrate the iodine liberated with
sodium thiosulphate solution. Near the end of the reaction (colour of solution pale yellow) add
2 ml of starch solution (3.1) and continue the titration until disappearance of the blue colour,
the total volume of sodium thiosulphate solution being D. Then add more potassium perman-
ganate solution until a faint blue colour returns. The total volume of potassium permanganate
solution used is called C.
The mass in grammes of sulphur equivalent to 1 ml of thiosulphate solution is :
A X C X 0.2392
e=
O
BXD
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ISO/R 682-1968 (€
3.4 Standard potassium iodate solution (0.03 N)
Prepare a solution containing 1.12 g of potassium iodate and 12 g of potassium iodide per litre.
Standardize it by repeating the sequence of operations employed in standardizing the thiosul-
phate (3.3), replacing potassium permanganate by potassium iodate solution; (a volume F of the
latter requiring a volume G of sodium thiosulphate).
The mass in grammes of sulphur equivalent to 1 ml of potassium iodate solution is
AXCXGX0.2392-eXG
--
E=
O
BDF F
3.5 Stannous chloride solution
Add 7 ml of concentrated hydrochloric acid to 10 g of SnCl, .2H20. Heat to aid dissolution.
Cool and add 95 ml of cold water. This solution does not keep.
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