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By R. Nemenyi

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The oxygen and hydrogen being made to react using a catalyst to produce water vapour at ambient temperature and atmospheric pressure. The disadvantages common to both hydrogen and nitrogen lies in their bottling. In the course of compression and filling the gas gets contaminated. The dead weight of the cylinders is great, their transportation is costly and they are of small capacity (5 to 6 N m 3 ), consequently these gases are expensive. 4 VACUUM AS AN ATMOSPHERE Vacuum was originally used for annealing or brazing of those metals having a particular tendency to oxidation and gas absorption at elevated temperatures, such as tantalum, zirconium, titanium, niobium, etc.

The gas leaving the retort is cooled down in a cooler (6)filledwith cooling water (7). The unit marked 10 is the pressure-operated dryer. The gas is compressed to 6 to 15 atm by a compressor, then it is cooled down in a cooling water stream (8 and 9). Drying is effected by the pressure dryer (10). 2 the overall dimensions and characteristics of exothermic gas generators are listed. A photograph of an exothermic gas generator can be seen in Fig. 6. 5tol0 22to30 85 to 115 140 to 180 52 Exogas Atmospheres FIG.

The extent of oxidation is computed as follows: Initially we have 5 1 of air (20 v/o 0 2 ) at 10"4 torr. Finally at equilibrium we have 5 1 of gas in which pQ = 10~7 torr plus nickel oxide. Initial quantity of oxygen = PV = 10~4 x 5(20/100) = 10"41 torr. Final quantity of oxygen = 10" 7 x 5 = 5 x 10"71 torr. Quantity of oxygen forming oxide = 10 - 4 — (5 x 10 - 7 ) 1 torr = 995 x 10"71 torr. 81 x 10" 8 1. 88 x HT 7 g. 45 g cm" 3 this gives C. 5 x 10" 8 cm 3 NiO. 25 cm2 of the component's surface.

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