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