GB268637A - Improvements in and relating to gas analysis apparatus - Google Patents

Abstract

268,637. James, R. W., (Brown Instrument Co.). Sept. 3, 1926. Heat and temperature coefficients, apparatus for determining.-In apparatus for gas analysis of the kind in which the relative thermal conductivities of two gases to be compared determine the temperatures and resistances of current carrying elements located in cells in which the gases are received, the cells are formed in a metallic cell block, preferably of lead, aluminium, aluminium coated or impregnated with wax or varnish, or lead cast in a. shell of brass, aluminium &c., and the cell block is carried in a metallic housing formed with passages for conveying one or both of the gases to the cells, and preferably also with passages for receiving cooling-fluid. By this arrangement inequalities in the temperatures of the two gases are minimised. As shown in Figs. 3 and 5, a cavity D<1> in the housing D is adapted to receive the cell block E, which is drilled to form cells e, ea, for the two gases. Insulating- plugs inserted in the cell openings and secured by gland nuts carry conductors O, P, to the ends of which are secured helical wires R, a spider P<1> of insulating material being provided to centre the wires at their lower ends. The conductors O are slidably carried in the insulating plugs to permit of adjustment of the spacing between the convolutions of the wires and may be secured in position by set screws. PassagesD<2> for cooling- fluid are provided in the housing D, and passages D<3> D<5> therein, filled with glass beads, glass wool, steel wool, and absorbent cotton d<3>, serve to filter and cool the gas entering at B before it finally passes through an aluminium filter tube d<4> into a passage E<4> and so to the cells e. If desired, the lower end of the passage D<3> may contain water through which the gas is bubbled. The cell block E is of such size that a space is left between it and the housing D, which is supplied with gas, both from the passage E<4> through ports E<3>, and from the cells e whereby the temperature of the cell block is maintained slightly higher than that of the housing. Gas finally leaves the housing at B<1>. The cells ea are also fitted with resistances, but are filled with air and are connected to a closed chamber e<1> containing materials adapted to dry or to saturate the air in the cells ea. The resistances of the cells e and ea form alternate arms of a Wheatstone bridge, of which two opposed junctions are included in a circuit comprising a battery, ammeter, adjustable resistance and a balancing resistance S with sliding contact S<3>, whilst the remaining two opposed junctions are connected through a switch to a galvanometer. If it is required to determine both the carbon dioxide and carbon monoxide content of a gas, two of the units described above are used, in the first of which the carbon dioxide content is determined, using air as the comparision gas, whilst in the second, the gas from the first unit is passed to the cells em through the chamber e<1>, and the cells e are supplied with gas which has been passed through a furnace to convert the carbon monoxide to carbon dioxide. Conveniently the two units are connected to the same galvanometer through a switch, and the whole is so arranged that the galvanometer needle moves in one direction to indicate the carbon dioxide content and in the other to indicate the carbon monoxide content. In a simplified form the housing D essentially comprises a water jacket and no provision is made for filtering the gases, which pass to the cells through a single cooling passage.