catchment trap of the type shown in the drawings of u s pat no 4 774 069 the catalyst pack will consist of four layers of woven platinum rhodium wire made from an alloy of platinum with 10 wt based on the weight of alloy of rhodium all layers of the catalyst pack are to be made from wire of diameter of 0 076 mm woven into a gauze of mesh size 1024 interstices per sq cm which will give the cloth an open area of 57 the catchment trap will consist of three layers of interstitial ceramics cloth interleaved with two layer of palladium scavenger wire the ceramics cloth will consist of a ceramics material composed of 62 wt alumina 24 wt silica and 14 wt boria formed into fibers of diameter 11 mum which in turn will be spin into threads and woven to make a cloth of mesh size 50 interstices per sq cm which will give the cloth an open area of 52 6 the palladium layers will consist of palladium wire of diameter 0 080 mm woven into a gauze of mesh size 1024 interstices per sq cm giving an open area of 55 the.