Improvements in and relating to means for the detection and quantitative determination of combustible gas or vapour in an atmosphere

摘要

PICT:0645252/III/1 Means for detecting a combustible gas in an oxygen-containing atmosphere comprises a differential thermometer for measuring the heat generated by burning said gas in said atmosphere by a catalytic agent having two separate conduits whereby the atmosphere is divided into two substantially identical streams, one conduit containing one part of the differential thermometer embedded in the catalytic material whilst the other conduit contains the other part of the differential thermometer embedded in inactive material, the specific heat and heat conductivity of both materials being substantially the same. In the construction shown, a U-tube 8, 9 is held in a flue 19 by diaphragms 27, a partition 20 dividing the flue into two equal portions. A spirally-grooved wall 21 receives liquid from a boiler 23, and the presence of the grooves ensures that the flue, and thereby the active, 18, and inactive, 17, materials, is uniformly heated. A condenser 26 is provided. An electric circuit is completed when the mercury rises to a predetermined value in the limb 8 and an alarm bell is rung. This limb has a chart giving a direct reading of the amount of combustible gas present. In each case the inactive and active materials must offer the same resistance to air, and have similar heat conductances and specific heats. In a modification, a thermo-couple is used and a further modification utilizes a mercury bulb thermometer packed in the catalyst-no inactive component being present. A further modification, designed to operate at room temperatures (Fig. 1, not shown) has an inlet divided into two similar conduits-the active material being in one, and the inactive in the other-and the atmosphere may be drawn through the apparatus by a pump. Active materials specified are a mixture of manganese dioxide, copper oxide and silver oxide, a mixture of iodine pentoxide and sulphuric acid on a porous carrier, cupric oxide, silver oxide or cobaltic oxide; whilst inactive materials are a mixture of manganese dioxide and copper oxide, sulphuric acid in a carrier, magnesium silicates or alumina.