{HEAD ~ The aqueous solution} of sodium hydroxide, which is the heavier phase, contains most of {TAIL ~ the catalyst} 
contains
{ HEAD ~ The aqueous solution } of sodium hydroxide , which is the heavier phase , contains most of { TAIL ~ the catalyst }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL