The Determination of Trace Amounts of Carbon in Iron and Steel by the Tube Furnace Combustion-Conductometric Method
1985 Volume 71 Issue 14 Pages 1670-1676
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1985 Volume 71 Issue 14 Pages 1670-1676
The useful method is described for the determination of trace amount of carbon in iron and steel by the conductometry with the aid of microcomputer. That is, the carbon dioxide is evolved by combustion of the sample in the stream of oxygen and then absorbed into the sodium hydroxide solution for measurement of conductivity. The following results were obtained:
(1) The concentration of sodium hydroxide solution is decided by the theoretical calculation in order to measure the conductivity shift based on the absorption of the carbon dioxide below 100 μg as carbon and the reasonability of its concentration is also confirmed by the experiment. The optimum concentration is 0.0025 mol dm-3.
(2) Carbon of 0.5 μg can be determined by the present method, because the output of the conductivity cell is treated by the micro computer to improve S/N ratio.
(3) Carbon adsorbed on the sample surface can be eliminated by heating the sample at 430°C in oxygen stream or etching chemically the sample surface in the mixed acid solution.
(4) The certified values of the certified reference materials on the market show generally tendencies to be on the high side in 48 ppm because of carbon adsorbed on their surfaces.
(5) The present method is useful for the determination of carbon of ppm order in iron and steel because of the high sensitivity and the simplicity in the analytical procedure.
