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