Preferred catalyst comprises {HEAD ~ potassium antimonate} together with potassium sulfate and {TAIL ~ minor amounts} of zinc sulfate and cupric sulfate  
together with
Preferred catalyst comprises { HEAD ~ potassium antimonate } together with potassium sulfate and { TAIL ~ minor amounts } of zinc sulfate and cupric sulfate
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH