Sentence:  It was possible to make estimates of the quantum yield by observing the extent of reduction of a uranyl oxalate actinometer solution illuminated for a known time in a typical <WSD>reaction</WSD> cell and making appropriate conversions based on the differences in the absorption spectra of uranyl oxalate and of chlorine , and considering the spectral distribution of the light source . 
Meaning of the word marked with <WSD> tags:  (chemistry) a process in which one or more substances are changed into others