Alkaline thiourea process is thiourea leaching method under alkaline conditions.

　　1. Principle: thiourea forms a cationic complex with gold under the presence of alkaline and oxidizing agents. The main electrochemical reactions are:

　　2 (NH2) 2CS + 2OH-- 2E = (N2H3CS) 2 + 2H2O Au + (NH2) 2CS e = Au[(E)

　　(N2H3CS) 2 + 2H2O + 2E = 2 (NH2) 2CS + 2OH- Au[(NH2) 2CS]+ + (NH2) = = 2CS (2CS]+)

　　The total reaction is Au + 2 (NH2) 2CS = Au[(NH2) 2CS]2+ +e

　　2, advantages: alkaline thiourea method has selectivity for gold dissolution; alkaline thiourea method can be used in combination with cyanidation.