This step is optional, but is essential in the cases where {HEAD ~ the above described metal chlorides} are hygroscopic in {TAIL ~ ambient air} or inert to oxygen or carbon at its melting point 
are hygroscopic in
This step is optional , but is essential in the cases where { HEAD ~ the above described metal chlorides } are hygroscopic in { TAIL ~ ambient air } or inert to oxygen or carbon at its melting point
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH