ISO 4935:1989 pdf free.Steel and iron — Determination of sulfur content — Infrared absorption method after combustion in an induction furnace.
ISO 4935 is applicable to sulphur contents between 0,002 % (m/m) and 0,10 % (m/m). Specifies principle, reagents and material, apparatus, sampling, procedure, expression of results and test report. Annex A gives additional information on the international cooperative tests. Annex B represents the precision date graphically. Annex C deals with induction furnaces and infrared sulfur analysers.
3 Principle
Combustion of a test portion with accelerator at a high temperature in a high-frequency Induction furnace in a current of pure oxygen. Transformation of sulfur into sulfur dioxide.
Measurement by infrared absorption of the sulfur dioxide carried by a current of oxygen.
4 Reagents and materials
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity.
4.1 Oxygen, 99,5 % (rn/en) minimum.
An oxidation catalyst Icopper(ll) oxide or platinum) tube heated to a temperature above 450 °C must be used prior to a purifying unit (see annex C), when the presence of organic contaminants is suspected in the oxygen.
4.2 Pure iron, of known low sulfur contents less than
0,000 5 % (tn/rn).
4.3 SuItable solvent, appropriate for washing greasy or dirty test samples, for example, acetono.
4.4 Magnesium perchiorate, particle size:
from 0,7 mm to 1,2 mm.
4.5 Accelerator, tungsten, free of sulfur, or of known sulfur contents less than 0,000 5 % (rn/rn). The mesh size of the accelerator may be dependent on the type of apparatus used.
5 Apparatus
During the analysis, unless otherwise stated, use only ordinary
laboratory apparatus.
All volumetric glassware shall be class A, in accordance with
ISO 385-1, ISO 648 or ISO 1042 as appropriate. The apparatus required for combustion In a high-frequency Induction furnace and the subsequent Infrared absorption measurement of the evolved sulfur dioxide may be obtained commercially from a number of manufacturers. Follow the manufacturer’s Instructions for the operation of the equipment.
Features of commercial Instruments are given In annex C.