{HEAD ~ The invention} requires three chemicals CO2, {TAIL ~ Ca2}, and sodium chloride NaCl to produce NaHCO3 
requires
{ HEAD ~ The invention } requires three chemicals CO2 , { TAIL ~ Ca2 } , and sodium chloride NaCl to produce NaHCO3
HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH