REEVALUATION OF THE THIOCYANATE DOSIMETER FOR PULSE-RADIOLYSIS

The thiocyanate dosimeter (10(-2) mol dm(-3) SCN- in O-2-saturated water) has been standardised against the super-Fricke dosimeter (10(-2) mol dm(-3) Fe-II in O-2-saturated 0.4 mol dm(-3) H2SO4) using the hexacyanoferrate(II) dosimeter [5 x 10(-3) mol dm(-3) Fe(CN)(6)(4-) in O-2-saturated water] as a secondary standard. On the basis that G(Fe-III) = 1.67 x 10(-6) mol J(-1) and epsilon(FeIII) = 220.4 m(2) mol(-1) at 304 nm and 25 degrees C in the super-Fricke dosimeter, we obtain G epsilon[Fe(CN)(6)(3-)] = (3.47 +/- 0.06) x 10(-5) m(2) J(-1) at 420 nm and G epsilon(SCN)(2)(-) = (2.59 +/- 0.05) x 10(-4) m(2) J(-1) at 475 nm. These values remain unchanged when the solutions are saturated with air instead of O-2 and are doubled in N2O-saturated solution.