Relatively {HEAD ~ base metals} such as lead and {TAIL ~ cadmium}, specifically, may pass into solution in aqueous and especially in increasingly acid environment, decomposing water and liberating hydrogen 
Relatively { HEAD ~ base metals } such as lead and { TAIL ~ cadmium } , specifically , may pass into solution in aqueous and especially in increasingly acid environment , decomposing water and liberating hydrogen
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH