{HEAD ~ The iron} and sulphur contained in the residue remain for {TAIL ~ the most part} undissolved 
{ HEAD ~ The iron } and sulphur contained in the residue remain for { TAIL ~ the most part } undissolved
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH