The Farkas Actinometer 5M Ethanol in Water

The Farkas Actinometer (5M Ethanol in Water), in the Farkas actinometer the hydrogen evolved from 5M aqueous ethanol is measured. The Farkas actinometer appears to be very reliable for the 185 nm line emitted by the Hg low pressure arc. 

The other major line at 254 nm contributes to the H2 evolution only negligibly (128). 

The value of ((i(H2)=0.4 appears to be the most reliable. The higher values including 0.5 which are still currently used would give ti(sum of primary processes) 1 for many systems such as N2O (166), methanol (127), ethanol (128), isopropanol (129), di-t-butyl ether (87) and methyl-n-propyl ether (88), an unreasonable result. However, using ( (H2)=0.4, (Ksum of primary processes) approaches or equals but never exceeds unity. If normalized to the same actlnometer quantum yield value, results from different laboratories, for example, the H2 yield of 1M methanol in water ( cf. 127,166-168), agree within 10 percent. 

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