Synopsis A new apparatus f or the determination of dif fusible hydrogen in steel has been developed by using a gaschromatograph, a thermal conductivity detector, and a sequencer. The characteristics of the apparatus are as follows: (1) The lower limit of detection is 10 ml (N. T .J.), that is 5>< 10-4 ppm for 2 g specimen. (2) The minimum cycle time of measurement is 3 min. (3) l7Jieen samples can be measured in parallel when the measurement is carried out every one hour. (4) The measurement

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... wn above is automatically carried out by a programed sequencer. (5) The coefficient of variance of results (approximately 4 m1/100g) is about b %. The apparatus is useful not only for determination of dif fusible hydrogen in weld metal but also for determination of d/fusivity of hydrogen in iron, alloyed-steel and thin foil of amorphous iron and for measurement of permeability of hydrogen through steel. It was also revealed that for low hydrogen content specimens the glycerin volumetric method gave much lower results than those obtained by the present method.