ry lam ide ▁in ▁making ▁a ▁poly ac ry lam ide ▁gel , ▁hence ▁being ▁important ▁for ▁SD S - PA GE ▁and ▁western ▁bl ot . ▁ ▁Illustr ative ▁of ▁its ▁powerful ▁ox id izing ▁properties , ▁it ▁is ▁used ▁to ▁et ch ▁co pper ▁on ▁printed ▁circuit ▁bo ards ▁as ▁an ▁alternative ▁to ▁fer ric ▁ch lor ide ▁solution . ▁ ▁This ▁property ▁was ▁discovered ▁many ▁years ▁ago . ▁In ▁ 1 9 0 8 , ▁John ▁William ▁T urrent ine ▁used ▁a ▁dil ute ▁am mon ium ▁pers ulf ate ▁solution ▁to ▁et ch ▁co pper . ▁ ▁T urrent ine ▁we ighed ▁co pper ▁spir als ▁before ▁placing ▁the ▁co pper ▁spir als ▁into ▁the ▁am mon ium ▁pers ulf ate ▁solution ▁for ▁an ▁hour . ▁ ▁After ▁an ▁hour , ▁the ▁spir als ▁were ▁we ighed ▁again ▁and ▁the ▁amount ▁of ▁co pper ▁dissol ved ▁by ▁am mon ium ▁pers ulf ate ▁was ▁recorded . ▁ ▁This ▁experiment ▁was ▁extended ▁to ▁other ▁met als ▁such ▁as ▁nick el , ▁cad m ium , ▁and ▁iron , ▁all ▁of ▁which ▁yield ed ▁similar ▁results . ▁The ▁ox id ation ▁equation ▁is ▁thus : ▁ ▁( a q ) ▁+ ▁ ▁→ ▁ 2 ▁ ▁( a q ). ▁ ▁Am mon ium ▁pers ulf ate ▁is ▁a ▁standard ▁ing red ient ▁in ▁hair ▁ble ach . ▁ ▁Pers ulf ates ▁are ▁used ▁as ▁ox id ants ▁in ▁organ ic ▁chem istry . ▁For ▁example , ▁in ▁the ▁Min is