Elements for thermochemical gas analysis - by application of carrier and catalysts to platinum metal

Primary elements, esp., for thermochemical gas analysis apparatus, are made by covering a Pt-spiral with a suspension of Al2O3 in unsaturated Al(NO3)3 and methanol, then a similar suspension using H2O instead of methanol. After each addition the spiral is electrically heated to 600-700 degrees C for 15-20 sec. The treated spiral is then heated to 800-900 degrees C for 12-15 hrs. in a muffle furnace and allowed to cool slowly. A catalytically active coating is then applied using drops of PtCl4 and PdCl2 soln. alternately with electrical heating, as before, after addition of each drop. Finally the element is further heat treated at 800-900 degrees C for 12-15 hrs. The element has homogeneous structure and porosity and gives repeatable results of identical sensitivity.