of n hexane to do this various amounts of n hexane ranging up to 2000 ppm in air were injected into the circuit the flow rate of the latter being regulated at 1 l min at regular intervals 50 u03bcl samples of gas were withdrawn in order to measure the concentration of n hexane present in the circuit it was shown that the direct decomposition by uv of n hexane is negligible just as its absorption by the medium in contrast n hexane is virtually 100 decomposed in less than one hour when it passes through the photocatalytic medium though under weak uv irradiation according to the same process a 60 g m 2 glass web was impregnated in an aqueous solution containing 1 g l of a1100 silane and 5 g l of titanium dioxide sold under the name p25 by degussa held in suspension by appropriate means the web was impregnated in line at 0 6 m min the excess binder having been removed under a negative pressure of 90 mm of water column the product was baked at 300 u00b0 c for 30 minutes measurements of effectiveness in the liquid phase were then carried out in order to describe this material a circular specimen of web diameter 100 mm was placed at mid height in a 300 ml beaker the bottom and the edges of the receptacle having been rendered opaque the beaker is illuminated by a bank of uv a lamps 365 mm delivering a power of 3 5 mw cm 2 to the web an aqueous solution deionized water containing 10 mg l of phenol is poured into the device and is kept stirred magnetically the decrease in concentration of the phenol is then monitored samples being withdrawn at regular time intervals by.