基本信息
摘要：137,547. Adams, H. E. F. Goold-, Bousfield, W. R., and Todd, G. W. Sept. 28, 1917. Hygrometric apparatus.-Water vapour is detected by passing the gas to be tested over a salt or substance having a definite critical hydration pressure, for example the alkaline chloride or nitrate, which takes up water only if the partial pressure of the water vapour is above the critical hydration pressure of the salt and thereby becomes a conductor, closing an electric circuit. The apparatus shown is suitable for testing a mixture of nitrogen and hydrogen, used for the synthetic production of ammonia, for the presence of oxygen. The gas to be tested is continuously sampled by a by-pass tube a and passes in succession through a drying-tube b, safety tube c, catalyst chamber d in which any oxygen present combines with hydrogen to form water vapour, then through the detecting salt and finally through a sulphuric-acid bubbler q. The dried detecting- salt may be placed between two wire gauze electrodes e, f, Fig. 2, arranged in brass tubes h cemented in a glass tube i. The salt forms part of an electric circuit containing an ammeter or galvanometer g, or a relay n, or both. The relay n may actuate a bell o, or other audible or visible alarm, or means for electro-magnetically cutting off the main supply of gases. A resistance r, equal to that of the salt when moist, may be put in parallel with the detector by a switch s for testing the circuit. A two-way valve p enables gases to be passed through the apparatus at starting without passing through the detector. The detector may be tested by drawing gas free from air or oxygen through a bubbler b' containing 20 per cent sulphuric acid having a definite vapour pressure. An alternative form of detector is shown in Fig. 4, and consists of two fine platinum wires t, t<1> wound round an insulating rod t<2>, on which a thin film of the detecting-salt has been deposited.
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