Patent GB-554792-A (GB)
Title: An improved electrical apparatus for the analysis or identification of gases, vapours and the like
IPC: G01N27/64
Filed: 1941-10-16
Abstract: 554,792. Determining physical qualities of materials. GEOPHYSICAL PROSPECTING CO., Ltd., TEMPLETON, J. C., and WINKLER, L. T. Oct. 16, 1941, No. 13347. [Class 37] Qualitative or quantitative analysis or identification of mixed gases or vapours is effected by producing ions in the mixture, grouping the ions of the different constituent gases by virtue of the different ion-mobilities, selectively collecting one or more groups of the ions on different electrodes, and measuring the charge imparted to one or more of these electrodes, this charge being a measure of the quantity of gas present having that particular ion-mobility. A rectangular or other chamber 10 is provided with inlet and outlet valves 12, 13 for introducing a quantity of the gas to be analysed. Electrodes 14, 15 are provided for producing an electric field across the chamber and means are provided adjacent to the electrode 15 for ionizing a small volume of the gas. This may be effected through an aluminium window 16 in the electrode 15 or a window 17 in a wall of the chamber by means of X-rays or radio-active material, or it may be effected internally in the chamber by heat or photo-electric action. On two other walls are electrodes for producing a transverse electric field, one electrode 18 being a single plate and the other consisting of separate plates 19, 20, 21. The electrode 19 is narrow compared with the electrodes 20, 21, which are connected to constitute a single electrode. The electric fields are provided successively by a continuously rotated switch 22. An instrument 25 is provided for measuring a charge imparted to the electrode 19 by ions collected on it. When the chamber has been filled with gas, an electric field is established between the electrodes 14, 15 and maintained until any ions fortuitously present are collected on the electrode 15. A small quantity of gas near this electrode is then ionized and the field between the electrodes 14, 15 is reversed to cause the ions to travel towards the electrode 14. Owing to the difference in their ion-mobilities they group themselves in layers. The field is then cut off and a field is applied between the electrode 18 and the electrodes 19, 20, 21 to cause the ions to travel towards the latter. The ions of the layer opposite the electrode 19 are collected thereon and the resulting charge is measured by the instrument 25, which thus indicates the number of ions and therefore the presence of that particular constituent gas or vapour which is present in the mixture. Two or more constituents may be identified simultaneously by collecting their ions on separate electrodes and measuring the charges produced by them. In a modification the electrode 19 is traversed across the chamber to collect the charge, instead of establishing a transverse field. The atmosphere may be examined for the presence of poison gas, in which case the electrodes may be freely exposed to the atmosphere or may be enclosed in an open-ended chamber through which a gentle current of air is passed. The measurement may be amplified so that remote indicators can be used and the distribution of poison gas over an area mapped out. In geophysical investigations the gases are extracted from the soil from any selected depth and introduced into the apparatus.