<Original Papers>On Some Improvements of Apparatus for the Vacuum Heating Method of Hydrogen Analysis in Iron and Steel

The heat extraction method for the analysis of hydrogen in iron and steel was standardized in 1938 by the 19th Sub-committee of "Gakujutzu-Shinkokai". By the measurement of the exhausting capacity of the mercury diffusion pump and the automatic "Sprengel" pump, it becomes clear that the dead space which is exhausted by the "Sprengel" pump should be as small as possible. In a gas collecting system using these two pumps in series, if the dead space is as small as 30-40 cc and the inner diameter of the capillaries for the mercury dropping tube of "Sprengel" pump are 1.8-2.2mm, it is possible to collect gas extracted from the metal to the amount of about 6-7 cc in 30 min. As it usually takes about one hour or more to extract hydrogen in the metal, if two or three series of extracting systems could be made, each consisting of only one diffusion pump and gas reservoir of 3-5 l, they might be collected by only one collecting system. The weak point of the standard heat extraction method is the time required for analyzing a sample, but, it is possible to make two or three analyses at the same time by the above mentioned arrangement. By the setting of a special micro gas burrette series, when explosion pipette and combustion pipette are compared for hydrogen, carbon monoxide and their mixtures with nitrogen the range of error is within 0.007 cc. And it is clear a combustion pipette, with a platinum wire spiral of 0.125 mm diameter, ought to be used in heating and promoting the oxidation, because explosion by the spark gap causes very complicated oxidation of the combustible gases existing in nitrogen and tends to reduce the value of nitrogen content and to increase the value of hydrogen content. Four absorption pipettes of different types are compared in this study by using 33% KOH aq. solution as the absorption reagent for CO_2 and the best one among them is determined. Comparisons of the spring balance used to absorb H_2O by P_2O_5 and by dissociation of water vapour on the heated tungsten wire spiral for the determination of water vapour in extracted gases are made