body which provides rigidity and a silver metal coating which provides the noble metal reaction surface inside the vessel conventional silver metal vessels begin to slump at about 850 u00b0 c the ceramic body of the present vessel prevents slumping up to temperatures near the melting point of silver 960 u00b0 c the initial ceramic structure is an unglazed porous ceramic vessel having interconnecting open pores water will seep or flow out of the ceramic wall of such a vessel the open porosity of the ceramic vessel is preferably about 5 to about 40 volume percent and more preferably from 10 to 25 volume percent the vessel may be composed of ceramic materials conventionally used in high temperatures reaction crusibles such materials are inert and nonreactive with molten agno 3 and hot silver examples of such materials include alumina thoria zirconia magnesia zeolite etc vessels made of alumina and of thoria were used in the examples reaction vessels of many types may be produced in this invention examples include crucibles boats reaction tubes etc a reaction crucible and reaction boat were produced and used in the examples reaction vessels also include enclosed reaction chambers the first step of the process coats the inner or reaction surfaces of the vessel and infiltrates the interconnecting open pores with molten agno 3 one method of accomplishing this is by immersing.