passing {HEAD ~ said reactants} at {TAIL ~ 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 catalyst 
at
passing { HEAD ~ said reactants } at { TAIL ~ 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 catalyst
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH