The Solvay process uses poisonous ammonia gas with {HEAD ~ a complex column system} to extract {TAIL ~ the said products} 
to extract
The Solvay process uses poisonous ammonia gas with { HEAD ~ a complex column system } to extract { TAIL ~ the said products }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL