硝酸银滴入氨水：氨水过量,生成银氨离子：
Ag+ + 2NH3 = Ag(NH3)2+
氨水滴入硝酸银溶液:先沉淀,后溶解.
Ag+ + NH3.H2O = AgOH + NH4+
AgOH + 2NH3.H2O = Ag(NH3)2+ + 2H2O