Preferred for {HEAD ~ the heteropolyacid} is at least one type selected from among silicomolybdic acid, phosphorotungstic acid, silicotungstic acid, phosphoromolybdic acid and {TAIL ~ silicotungstomolybdic acid} 
Preferred for { HEAD ~ the heteropolyacid } is at least one type selected from among silicomolybdic acid , phosphorotungstic acid , silicotungstic acid , phosphoromolybdic acid and { TAIL ~ silicotungstomolybdic acid }
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL