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