passing said reactants at {HEAD ~ a known preselected concentration} through said bundle of parallel tubes wherein the inlet temperature is high enough to initiate said catalytic conversion throughout said volume of {TAIL ~ catalyst} 
passing said reactants at { HEAD ~ a known preselected concentration } through said bundle of parallel tubes wherein the inlet temperature is high enough to initiate said catalytic conversion throughout said volume of { TAIL ~ catalyst }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL