GB698204A - Improvements in apparatus for the decomposition of alkali metal amalgam - Google Patents

Abstract

<PICT:0698204/III/1> <PICT:0698204/III/2> A vertical appartus for the decomposition of alkali metal amalgam to alkali metal hydroxide, of the kind having a mass of pieces of graphite or other contact material between upper and lower perforated plates of electrically conductive, non-amalgamateable material, e.g. graphite or silicon iron, wherein amalgam is introduced at the top and spread by the upper plate, is characterized in that a plurality of additional perforated plates, also of non-amalgamateable conductive material, are inserted between the upper and lower plates with layers of contact material between them, which additional plates fit closely against the wall of the apparatus to cause reacting fluids to pass through the openings in the plates. The plates, which may be flat, slightly sloped or frustro-conical, may have graphite spacing pieces, in the form of gaskets sealing against the apparatus wall, between them. The plates may have holes or slots, and holes or slots in adjacent plates may be staggered, or offset at an angle, respectively. Where the plates are slotted they may be in the form of spaced-apart strips laid side by side. Mercury amalgam enters amalgam rinsing compartment 8 at 12 and passes through perforated plates 7 and filling 71 countercurrent to water or steam entering at 10. The plates 7 and filling 71 are of material which is unreactive with water and alkali amalgam and non-electrically conducting e.g. stoneware or rubber-lined steel. The wash water or steam is discharged at 11 and amalgam passes through liquid seal 811 to decomposition chamber 1. The amalgam passes down through perforated graphite cathode plates 3 with spacing gaskets 5 and rings or shaped pieces of graphite filling 31 to mercury outlet 2, while water enters at 61 and caustic alkali solution is withdrawn at 16. The outer holes 141, 151 of the plates 3, Fig. 2, may be countersunk below the surface, and the inner hole 1411, 1511 may be surrounded by projecting flanges, so that amalgam flows through the outer holes and hydrogen and caustic alkali through the inner. The total area of perforations should be 1/6 -\ba1/2 the solid surface area of the plate and the minimum size of openings and the space between plates should be 1/16 -\ba1/2 inch.